Oxide superconductor and production method therefor

Abstract

An oxide superconductor according to an embodiment includes an oxide superconducting layer that has a first surface and a second surface opposite the first surface, and that includes a first region and a second region. The first region has a continuous perovskite structure and includes rare earth elements, barium (Ba), and copper (Cu). The rare earth elements include a first element that is praseodymium (Pr), a second element, a third element, and a fourth element. The first element, the second element, the third element, and the fourth element are all different elements. The second region is amorphous or polycrystalline and includes, at the second surface, first portions that extend in a first direction parallel to the first surface and second portions that are different from the first portions and extend in a second direction parallel to the first surface and intersecting the first direction. The volume percent of the second region is 0.001-1.10%.

Description

Oxide superconductor and method for manufacturing the same

[0001] Embodiments of the present invention relate to oxide superconductors and methods for manufacturing the same.

[0002] Oxide high-temperature superconductors were discovered in 1986 by Bednorz and Mueller, but the main applications of copper oxide superconductors are those that use copper. Copper oxide superconductors are, as the name suggests, superconductors that use copper, and other types such as iron-based superconductors and nickel-based superconductors have also been reported. However, among the reported superconductors, copper oxide superconductors are considered to have the highest performance and practicality.

[0003] Among copper oxide superconductors, the first to be developed were the first-generation (1G superconducting wires), known as Bi-based superconductors. Bi-based superconductors are superconductors containing Bi, Sr, Ca, and Cu, and were characterized by improved superconducting properties when Bi was substituted with Pb. However, the metal that could be used as the sheath material for Bi-based superconductors needed to be a metal that could maintain its metallic state even after the internal superconductor was oxidized.

[0004] Currently, the only metals that can be used as sheathing materials for Bi-based superconductors are precious metals, and their high price is a practical problem. Bi-based superconducting wires using Ag (silver) as sheathing material have been put into practical use, and sales volume increased for a time. Furthermore, the world's first power transmission cable test using this wire was conducted in the suburbs of New York, and it was confirmed that the superconducting wire could be used in the same way as ordinary wires even when hundreds of thousands of volts of voltage were applied to it.

[0005] The 1G superconducting wire seemed poised for success, but the high cost of the sheath material became a problem. The optimal material for the sheath is silver (Ag), but the minimum amount of Ag required is approximately 60% of the total, so the price problem could not be solved.

[0006] Then came the era of 2G superconducting wire applications. 2G superconducting wires have Dy inside, with a diameter of approximately 50 nm. ２ O ３ YBa containing many particles ２ Cu ３ O ６．９３It is a superconducting wire. This wire is made by a method called Metal-organic deposition using trifluoroacetates (TFA-MOD method). The operating temperature range of the wire is 69 - 77K, which is a temperature range below the liquid nitrogen temperature.

[0007] This superconducting wire has mainly been applied in low magnetic fields below 1T. In applications in magnetic fields above approximately 1T at 20 - 30K, Dy particles with a diameter of around 50nm ２ O ３ enter into YBa ２ Cu ３ O ６．９３ superconducting wires, resulting in low performance and no consideration for application.

[0008] If asked what kind of superconductor enables magnetic field application, it is a superconductor with a non-superconducting structure of the same size as the quantum flux penetrating at the operating temperature of the superconductor, that is, a structure called an artificial pin. The size of the quantum flux depends on the type of superconductor used and the critical temperature (critical temperature: T ｃ ) value.

[0009] For example, in the case of a YBa ２ Cu ３ O ６．９３ superconductor, when it is a superconductor with the maximum critical current density (critical current density: J ｃ ) at 77K, its T ｃ is 90.7 ± 0.1K. When the above superconductor is cooled, it is said that the size of the quantum flux of the generated magnetic field is around the coherence length. At 30K and 77K, the sizes of the respective quantum fluxes are approximately 5nm and approximately 50nm. In this specification, for simplicity of explanation, the sizes of the quantum fluxes in YBa ２ Cu ３ O ６．９３ superconductors at 30K and 77K are all set to 5nm and 50nm.

[0010] The quantum flux and the superconducting state cannot coexist in some superconductors. When the quantum flux penetrates into the superconductor, the superconducting state collapses. However, in YBa２ Cu ３ O ６．９３ In the case of superconductors, quantum magnetic flux and the superconducting state can coexist. However, if the quantum magnetic flux moves freely within the superconductor, the region where the properties deteriorate increases, and the superconducting properties in a magnetic field decrease.

[0011] YBa at 77K ２ Cu ３ O ６．９３ If a non-superconducting region of 50 nm in diameter exists inside a superconductor, the superconducting potential of the quantum magnetic flux is 100% when the quantum magnetic flux is inside the superconductor and 0% when it is inside the non-superconducting region. When the quantum magnetic flux moves 50 nm, the superconducting potential changes from 100% to 0%, and this potential difference generates stress in the quantum magnetic flux. This stress is called a pinning force, and artificial pins are used to create this pinning force.

[0012] As will be explained in more detail later, artificial pins have specific sizes, and using any other size will result in a reduced effectiveness. For this reason, this wire cannot be used with 30K.

[0013] Superconducting wires with high performance at 30K are the result of long-term development of BaZrO ３ Non-superconducting materials such as YBa ２ Cu ３ O ６．９３ This technique involves forming superconductors inside the superconductor. Known as the Artificial Pinning Center, it was first proposed by Professor M. Driscoll of the UK and remains a technology that many researchers worldwide continue to study.

[0014] The Artificial Pinning Center's features include BaZrO ３ Non-superconducting materials such as YBa ２ Cu ３ O ６．９３ This is because the lattice mismatch of superconductors is relatively small. Dy present in the aforementioned wire ２ O ３ The particle is YBa ２ Cu ３ O ６．９３ The lattice mismatch for superconductors reaches as high as 26%, causing them to grow independently of each other. However, BaZrO３ YBa ２ Cu ３ O ６．９３ The lattice mismatch for superconductors is around 9%.

[0015] This small lattice mismatch is YBa ２ Cu ３ O ６．９３ Superconductors and BaZrO ３ The shared lattice points, i.e., lattice bonds, are formed by BaZrO ３ This allows for the creation of smaller particles. However, this leads to the non-uniformity of the superconducting potential and nanoburn, which is combustion in the nanoscale, as will be discussed later. This is thought to be the reason why long-term operational results have not been reported for large-scale equipment to date. Furthermore, there were no presentations at EUCAS 2023 that attempted to understand and resolve this issue, and it is likely that the current situation will continue for the time being.

[0016] If we define a non-lattice-matched artificial pin as a Non-Lattice-matched pinning center (NLMP), then an Artificial Pinning Center is a Partially Lattice-matched pinning center (PLMP). Unless the problems described later are solved, it will be difficult to apply PLMPs to large-scale equipment at low temperatures of 20K or 30K, and new technologies are needed to avoid internal non-uniformity. Therefore, currently, there are no superconducting wires that have artificial pins that function at 20K or 30K and can be used stably for long periods of time.

[0017] To overcome this situation, the inventors have developed Clustered Atom-Replaced Pins (CARP), a Substantially Lattice-matched pinning center (SLMP). As will be explained in more detail later, these artificial pins are the world's first 5nm-sized artificial pins with a uniform and stable internal structure, and have a high probability of being highly uniform and stable for use.

[0018] In the current research stage, the most common type of CARP involves incorporating only 8% of the material that will become the CARP element. In other words, if the quantum magnetic flux is in a position to pass through one CARP, a pinning force acts that reduces the 8% superconducting potential.

[0019] Patent No. 3556586 Patent No. 6374365 Patent No. 6479251 Patent No. 6556674 Patent No. 6556769 Patent No. 7330152 Patent No. 7330153

[0020] T. Araki and I. Hirabayashi, Supercond. Sci. Technol. 16 (2003) R71-R94M. Hayashi et. al. Supercond. Sci. Technol. 31 (2018) 055013 (7pp) T. Araki, et. al. Supercond. Sci. Technol. 31 (2018) 065008 (8pp)

[0021] The problem that this invention aims to solve is to provide an oxide superconductor with improved properties in a magnetic field and a method for manufacturing the same.

[0022] The oxide superconductor of the embodiment has a first surface and a second surface facing the first surface, and comprises an oxide superconducting layer including a first region and a second region, wherein the first region has a continuous perovskite structure and comprises a rare earth element, barium (Ba), and copper (Cu), wherein the rare earth element is a first element which is praseodymium (Pr), at least one second element selected from the group consisting of neodymium (Nd), samarium (Sm), and europium (Eu), yttrium (Y), europium (Eu), gadridium It comprises at least one third element selected from the group consisting of nium (Gd), dysprosium (Dy), holmium (Ho), and erbium (Er), and at least one fourth element selected from the group consisting of yttrium (Y), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu), wherein the first element, the second element, the third element, and the fourth element are all different elements, and the third element and the fourth element are If the second element is not yttrium (Y), the atomic number of the second element is smaller than the atomic number of the third element, and the atomic number of the third element is smaller than the atomic number of the fourth element; if the third element is yttrium (Y), the fourth element is at least one element selected from the group consisting of erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu); if the fourth element is yttrium (Y), the atomic number of the second element is smaller than the atomic number of the third element, and An oxide superconductor comprising an oxide superconducting layer in which the third element is at least one element selected from the group consisting of europium (Eu), gadolinium (Gd), and dysprosium (Dy), the second region is amorphous or polycrystalline, and on the second surface, includes a first portion extending in a first direction parallel to the second surface and a second portion different from the first portion, extending in a second direction parallel to the second surface and intersecting the first direction, and the volume percentage of the second region is 0.001% or more and 1.10% or less.

[0023] Schematic cross-sectional view of the oxide superconductor of the first embodiment. Enlarged view including a part of the oxide superconducting layer of the first embodiment. Enlarged schematic cross-sectional view of the oxide superconducting layer of the first embodiment. Transmission electron microscope (TEM) image of the oxide superconducting layer of the first embodiment. Flowchart showing an example of coating solution preparation for the manufacturing method of the oxide superconductor of the first embodiment. Flowchart showing an example of a method for forming a superconductor film from the coating solution for the manufacturing method of the oxide superconductor of the first embodiment. Diagram showing a typical calcination profile for the manufacturing method of the oxide superconductor of the first embodiment. Diagram showing a typical final calcination profile for the manufacturing method of the oxide superconductor of the first embodiment. Diagram explaining the operation and effect of the oxide superconductor of the first embodiment. Diagram explaining the operation and effect of the oxide superconductor of the first embodiment. Diagram explaining the operation and effect of the oxide superconductor of the first embodiment. Diagram explaining the operation and effect of the oxide superconductor of the first embodiment. Enlarged view including a part of the oxide superconducting layer of the comparative example. Transmission electron microscope (TEM) image of the oxide superconducting layer of the comparative example. Diagram explaining the operation and effect of the oxide superconductor of the first embodiment. Diagram illustrating the operation and effects of the oxide superconductor of the first embodiment. Examples and comparative examples J ｃ - Diagram illustrating B-T measurement. Comparative Example 1 J ｃ -Figure showing the measurement results of B-T measurement. Explanatory diagram of the quantum magnetic flux state of Comparative Example 1. Explanatory diagram of the quantum magnetic flux state of Comparative Example 1. XRD measurement results of the superconducting film of Comparative Example 2. ω-scan measurement results of the superconducting film of Comparative Example 2. Transmission electron microscope (TEM) image of the oxide superconducting layer of Comparative Example 2A. Barium acetate used when preparing the coating solution of the comparative example. Barium acetate used when preparing the coating solution of Example 1. J of Example 1 ｃ -Figure showing the measurement results of B-T measurement. Explanatory diagram of the quantum magnetic flux state in Example 1. Explanatory diagram of the pinning effect in Example 1. Explanatory diagram of the pinning effect in the comparative example. J in Example 2 ｃ -Figure showing the measurement results of B-T measurement. Example 3, J ｃ - A diagram showing the measurement results of the B-T measurement. Diagram explaining the operation and effect of the example. Diagram explaining the operation and effect of the example. Diagram explaining the operation and effect of the example. Diagram explaining the operation and effect of the example. J of Example 6 ｃ -Figure showing the measurement results of B-T measurement. Comparative Example 3, J ｃ A diagram showing the measurement results of the B-T measurement.

[0024] In this specification, a crystallographically continuous structure is considered a "single crystal." Furthermore, even though the in-plane orientation degree ΔΦ of the orientation intermediate layer on a metal is 5 to 6 degrees, it is still considered that superconducting current flows as long as the grain boundary angles are 4.0 degrees or less. However, since superconducting lattices on metal substrates have lower properties than superconducting thin films on single crystals, even if crystalline bonding exists, the grain boundary angles may exceed 4 degrees. Therefore, even when the structure is crystallographically continuous and a superconducting current of nearly 100% is obtained, it will be considered a single crystal in this specification, but only when applied to a metal substrate.

[0025] In this specification, PA (Pinning Atom) refers to a rare earth element that acts as an artificial pin in an oxide superconducting layer. PA forms a non-superconducting unit cell. The only rare earth element that functions as PA is praseodymium (Pr).

[0026] In this specification, SA (Supporting Atom) is a rare earth element that promotes the clustering of artificial pins. The trivalent ionic radius of SA is smaller than that of PA, and larger than that of MA, which will be described later.

[0027] In this specification, MA (Matrix Atom) refers to a rare earth element that forms the matrix phase of an oxide superconducting layer.

[0028] In this specification, CA (Counter Atom) refers to a rare earth element that forms clusters with PA and SA. The trivalent ionic radius of CA is smaller than that of MA.

[0029] Furthermore, the types and concentrations of elements contained in oxide superconductors can be identified, for example, using Secondary Ion Mass Spectrometry (SIMS) or Energy Dispersive X-ray Spectroscopy (EDX). In addition, the dimensions of each part of the oxide superconductor can be measured, for example, from images obtained by Transmission Electron Microscopy (TEM).

[0030] The oxide superconductor of the embodiment will be described below with reference to the drawings.

[0031] (First Embodiment) The oxide superconductor of the first embodiment includes an oxide superconducting layer having a first surface and a second surface facing the first surface, and comprising a first region and a second region. The first region has a continuous perovskite structure and comprises rare earth elements, barium (Ba), and copper (Cu). Rare earth elements include a first element, which is praseodymium (Pr); a second element selected from the group consisting of neodymium (Nd), samarium (Sm), and europium (Eu); a third element selected from the group consisting of yttrium (Y), europium (Eu), gadolinium (Gd), dysprosium (Dy), holmium (Ho), and erbium (Er); and a fourth element selected from the group consisting of yttrium (Y), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu). The first, second, third, and fourth elements are all different elements. If the third and fourth elements are not yttrium (Y), the atomic number of the second element is less than that of the third element, and the atomic number of the third element is less than that of the fourth element. If the third element is yttrium (Y), the fourth element is at least one element selected from the group consisting of erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu). If the fourth element is yttrium (Y), the atomic number of the second element is less than that of the third element, and the third element is at least one element selected from the group consisting of europium (Eu), gadolinium (Gd), and dysprosium (Dy). The second region is amorphous or polycrystalline and includes, on the second plane, a first portion extending in a first direction parallel to the second plane, and a second portion that, unlike the first portion, extends in a second direction parallel to the second plane and intersecting the first direction. In the oxide superconducting layer, the volume percentage of the second region is 0.001% or more and 1.10% or less.

[0032] Figure 1 is a schematic cross-sectional view of an oxide superconductor according to the first embodiment.

[0033] The oxide superconductor of the first embodiment is a superconducting wire. The oxide superconductor of the first embodiment is suitable for applications under conditions where a magnetic field is applied, such as superconducting coils, superconducting magnets, MRI equipment, magnetic levitation trains, or SMES (Superconducting Magnetic Energy Storage). The oxide superconductor of the first embodiment is also applicable to power transmission cables under conditions where a magnetic field is applied.

[0034] As shown in Figure 1, the oxide superconductor 100 comprises a substrate 10, an intermediate layer 20, an oxide superconducting layer 30, and a metal layer 40. The substrate 10 enhances the mechanical strength of the oxide superconducting layer 30. The intermediate layer 20 is a so-called oriented intermediate layer. The intermediate layer 20 is provided to orient the oxide superconducting layer 30 and form a single crystal when the oxide superconducting layer 30 is formed. The metal layer 40 is a so-called stabilization layer. The metal layer 40 protects the oxide superconducting layer 30. Furthermore, the metal layer 40 has the function of diverting the current and stabilizing it even if the superconducting state becomes partially unstable during actual use of the oxide superconductor 100 as a superconducting wire.

[0035] The substrate 10 is a metal such as a nickel-tungsten alloy. The intermediate layer 20 is made of, for example, yttrium oxide (Y) from the substrate 10 side. ２ O ３ ), yttria-stabilized zirconia (YSZ), cerium oxide (CeO ２ The layer configuration of the substrate 10 and the intermediate layer 20 is, for example, nickel-tungsten alloy / yttrium oxide / yttria-stabilized zirconia / cerium oxide. In this case, an oxide superconducting layer 30 is formed on the cerium oxide.

[0036] The substrate 10 may be, for example, a single crystal layer that is lattice-matched with the oxide superconducting layer 30. The single crystal layer may be, for example, lanthanum aluminate (LaAlO). ３ (Hereafter, this will also be referred to as LAO). In this case, the intermediate layer 20 can be omitted.

[0037] Furthermore, for the substrate 10 and intermediate layer 20, for example, an IBAD (Ion Beam Assisted Deposition) substrate can be used. In the case of an IBAD substrate, the substrate 10 is an unoriented layer. The intermediate layer 20 consists of, for example, a five-layer structure. For example, the bottom two layers are unoriented layers, an orientation-origin layer manufactured by the IBAD method is formed on top of them, and two oriented metal oxide layers are formed on top of that. In this case, the uppermost oriented layer is lattice-matched with the oxide superconducting layer 30.

[0038] The oxide superconducting layer 30 has a first surface (F1 in Figure 1) and a second surface (F2 in Figure 1) opposite to the first surface F1. The first surface F1 and the second surface F2 are, for example, parallel. The direction parallel to the second surface F2 is defined as the first direction, the direction parallel to the second surface F2 and intersecting the first direction is defined as the second direction, and the direction from the first surface F1 toward the second surface F2 is defined as the third direction. The second direction is, for example, perpendicular to the first direction.

[0039] Hereinafter, the oxide superconducting layer 30 may be referred to as the superconducting film.

[0040] Figures 2(a) and 2(b) are enlarged views including a portion of the oxide superconducting layer of the first embodiment. Figure 2(a) is a top view, and Figure 2(b) is a cross-sectional view. Figure 2(a) is a top view of the second surface F2 of the oxide superconducting layer 30. Figure 2(b) is a cross-sectional view perpendicular to the second surface F2 of the oxide superconducting layer 30.

[0041] The oxide superconducting layer 30 includes a main region 30a and a sub-region 30b. The main region 30a is an example of a first region. The sub-region 30b is an example of a second region.

[0042] The main region 30a has superconducting properties. The sub-region 30b does not have superconducting properties.

[0043] The main region 30a contains rare earth elements, barium (Ba), and copper (Cu). The rare earth elements include a first element which is praseodymium (Pr), at least one second element selected from the group consisting of neodymium (Nd), samarium (Sm), and europium (Eu), at least one third element selected from the group consisting of yttrium (Y), europium (Eu), gadolinium (Gd), dysprosium (Dy), holmium (Ho), and erbium (Er), and at least one fourth element selected from the group consisting of yttrium (Y), dysprosium (Dy), holmium (Ho), and erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu). The first, second, third, and fourth elements are all different elements.

[0044] If the third and fourth elements are not yttrium (Y), the atomic number of the second element is smaller than that of the third element, and the atomic number of the third element is smaller than that of the fourth element. Also, if the third element is yttrium (Y), the fourth element is at least one element selected from the group consisting of erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu). Also, if the fourth element is yttrium (Y), the atomic number of the second element is smaller than that of the third element, and the third element is at least one element selected from the group consisting of europium (Eu), gadolinium (Gd), and dysprosium (Dy).

[0045] In the first embodiment, the first element is PA (Pinning Atom). The second element is SA (Supporting Atom). The third element is MA (Matrix Atom). The fourth element is CA (Counter Atom).

[0046] The main region 30a has a continuous perovskite structure. The main region 30a is, for example, a single crystal. The perovskite structure is, for example, REBa ２ Cu ３ O ７－ｙ This is denoted as (-0.2 ≤ y ≤ 1) (hereinafter referred to as REBCO), where RE is a rare earth element.

[0047] As shown in Figures 2(a) and 2(b), the main region 30a includes, for example, a plurality of first blocks 30a1 and a plurality of second blocks 30a2. The boundaries of each block are, for example, low-angle grain boundaries 30x where the difference in the direction of the c axis between the blocks on either side of the boundary is small. The difference in the direction of the c axis is, for example, 1.0 degree or less on a single crystal and about 6.0 degrees or less on a metal substrate. The average value of the difference in the direction of the c axis is, for example, 1.0 degree or less on a single crystal and 6.0 degrees or less on a metal substrate.

[0048] Each block is a collection of unit cells. Hereafter, a single block may be referred to as a collection of unit cells.

[0049] While block sizes are typically 50 nm x 200 nm, the size can vary depending on the firing temperature and the control of the gas volume, which affects the growth conditions. For example, some blocks may simply become smaller, such as 25 nm x 100 nm, while others may become longer in one direction, such as 50 nm x 300 nm.

[0050] Each first block 30a1 and each second block 30a2 are single crystals. In the first block 30a1, for example, the a-axis of the perovskite structure extends along a first direction, and the b-axis of the perovskite structure extends along a second direction. Similarly, in the second block 30a2, for example, the b-axis of the perovskite structure extends along a first direction, and the a-axis of the perovskite structure extends along a second direction.

[0051] In both the first block 30a1 and the second block 30a2, for example, the c-axis of the perovskite structure extends along a third direction. In the main region 30a, the c-axis of the perovskite structure extends along a direction perpendicular to the substrate 10.

[0052] The first element contained in the main region 30a is so-called PA (Pinning Atom), the second element is so-called SA (Supporting Atom), the third element is so-called MA (Matrix Atom), and the fourth element is so-called CA (Counter Atom).

[0053] The oxide superconducting layer 30 of the first embodiment includes so-called second-generation clustered atom replacement artificial pins (2nd-CARPs). A first element, PA, a second element, SA, and a fourth element, CA, form the CARPs.

[0054] In the main region 30a, the ratio of the atomic concentration of the third element to the sum of the atomic concentrations of the first element, the second element, the third element, and the fourth element is, for example, 60% or more and 95% or less.

[0055] The main region 30a contains, for example, fluorine (F). The atomic concentration of fluorine (F) in the main region 30a is, for example, 2.0 × 10⁻⁶. １５ atoms / cm ３ The above 5.0 x 10 １９ atoms / cm ３ The following applies:

[0056] The main region 30a contains, for example, carbon (C). The atomic concentration of carbon (C) in the main region 30a is, for example, 1.0 × 10⁻¹⁴. １７ atoms / cm ３ The above 5.0 x 10 ２０ atoms / cm ３ The following applies: The fluorine and carbon contained in the main region 30a are residual elements resulting from the deposition of the oxide superconducting layer 30 by the TFA-MOD method. The fluorine and carbon in the main region 30a are present, for example, in the low-angle grain boundaries 30x of the main region 30a.

[0057] The fluorine contained in the oxide superconducting layer 30 is, for example, 2.0 × 10 １６ atoms / cm ３ That concludes the explanation. Furthermore, the amount of carbon contained in the oxide superconducting layer 30 is, for example, 1.0 × 10 １８ atoms / cm ３ That's all.

[0058] Subregion 30b is amorphous or polycrystalline. Subregion 30b does not have a continuous perovskite structure. Subregion 30b is a non-superconducting region.

[0059] As shown in Figures 2(a) and 2(b), the sub-region 30b is, for example, tangent to the second surface F2. As shown in Figures 2(a) and 2(b), the sub-region 30b includes a plurality of first portions 30b1 and a plurality of second portions 30b2. On the second surface F2, the first portions 30b1 extend, for example, in a first direction. The second portions 30b2 extend, for example, in a second direction. On the second surface F2, the first portions 30b1 and the second portions 30b2 intersect each other.

[0060] As shown in Figure 2(b), the sub-region 30b is provided, for example, along the low-angle grain boundary 30x of the main region 30a. The sub-region 30b is provided, for example, on the side of the second surface F2 of the low-angle grain boundary 30x of the main region 30a.

[0061] In the second surface F2, for example, at least a portion of the sub-region 30b is provided at the boundary between the first block 30a1 and the second block 30a2.

[0062] The volume ratio of the sub-region 30b to the oxide superconducting layer 30 is, for example, 0.001% or more and 1.10% or less.

[0063] The volume ratio of the sub-region 30b can be calculated, for example, by multiplying the area ratio of the sub-region 30b obtained from the TEM image of the second surface F2 of the oxide superconducting layer 30 by the ratio of the depth of the sub-region 30b to the thickness of the oxide superconducting layer 30, obtained from the TEM image of the cross-section perpendicular to the second surface F2 of the oxide superconducting layer 30. The area ratio of the sub-region 30b is, for example, the median value obtained from measurements at multiple locations. The ratio of the depth of the sub-region 30b to the thickness of the oxide superconducting layer 30 is also the median value obtained from measurements at multiple locations.

[0064] The area ratio of the second surface F2 of the sub-region 30b is, for example, 0.03% or more and 10% or less.

[0065] For example, to determine the area ratio of sub-region 30b, a TEM image of a 100 nm × 100 nm region of the second surface F2 is used.

[0066] The width of the second surface F2 of the first portion 30b1 in the direction perpendicular to the elongation direction is, for example, 1 nm or more and 10 nm or less. Similarly, the width of the second surface F2 of the second portion 30b2 in the direction perpendicular to the elongation direction is, for example, 1 nm or more and 10 nm or less.

[0067] The depth of the sub-region 30b in the direction from the second surface F2 to the first surface F1 is, for example, 0.03% to 10% of the thickness of the oxide superconducting layer 30 in the direction from the second surface F2 to the first surface F1.

[0068] The subregion 30b contains, for example, barium (Ba). For example, the atomic concentration of barium (Ba) contained in the subregion 30b is higher than the atomic concentration of barium (Ba) contained in the main region 30a.

[0069] The sub-region 30b is thought to be formed when decomposition products and impurities of the raw material acetate present in the solution segregate at the grain boundaries during the formation of the oxide superconducting layer 30. It is thought that decomposition products and impurities of the raw material acetate are segregated in the sub-region 30b.

[0070] The thickness of the oxide superconducting layer 30 is, for example, 0.1 μm or more and 10 μm or less.

[0071] The metal layer 40 may be an alloy, for example, with silver (Ag) or copper (Cu) as the base metal. It may also contain small amounts of precious metals such as gold (Au).

[0072] Figure 3 is an enlarged schematic cross-sectional view of the oxide superconducting layer of the first embodiment. Figure 3 is an enlarged schematic cross-sectional view of the oxide superconducting layer 30 viewed from above, i.e., from the c-axis direction. Each rectangle represents a unit cell in the single crystal.

[0073] Figure 3 illustrates the case where PA is praseodymium (Pr), SA is samarium (Sm), MA is yttrium (Y), and CA is thulium (Tm). In other words, it illustrates the case where the first element is praseodymium (Pr), the second element is samarium (Sm), the third element is yttrium (Y), and the fourth element is thulium (Tm).

[0074] The main region 30a of the oxide superconducting layer 30 is composed of unit cells of PBCO containing praseodymium (Pr), SmBCO containing samarium (Sm), YBCO containing yttrium (Y), and TmBCO containing thulium (Tm).

[0075] The rectangles representing the PrBCO, SmBCO, and TmBCO unit cells are labeled Pr, Sm, and Tm, respectively. The blank rectangles in the diagram represent the unit cells of the matrix phase, YBCO.

[0076] Within the main region 30a, unit cells of PrBCO, SmBCO, and TmBCO form aggregates within the matrix phase, YBCO. These aggregates are called clusters. In Figure 3, the regions enclosed by thick solid lines represent clusters.

[0077] PrBCO is a non-superconductor. Clusters containing PrBCO function as artificial pins in the oxide superconducting layer 30.

[0078] Clusters are dispersed within the oxide superconducting layer 30. The clusters are segregated with the first, second, and fourth elements. For example, praseodymium (Pr), samarium (Sm), and thulium (Tm) are segregated in the clusters.

[0079] The atomic concentrations of the first element, the second element, and the fourth element within the cluster are higher than, respectively, the atomic concentrations of the first element, the second element, and the fourth element in the surrounding area of ​​the cluster.

[0080] In the cross-section of the oxide superconducting layer 30, the cluster size is, for example, between 1 nm square and 10 nm square. In the cross-section parallel to the second surface F2 or perpendicular to the second surface F2, the cluster size is, for example, between 1 nm square and 10 nm square.

[0081] The main region 30a includes a portion smaller than 10 nm square containing the first element, the second element, and the fourth element. A cluster is an example of the above portion.

[0082] The relationship between the trivalent ionic radii of praseodymium (Pr), samarium (Sm), yttrium (Y), and thulium (Tm) is Pr > Sm > Y > Tm. The cluster consists of PrBCO and SmBCO containing rare earth elements larger than the matrix phase YBCO, and TmBCO containing rare earth elements smaller than YBCO. Hereinafter, unit cells containing rare earth elements larger than the matrix phase will be referred to as large unit cells, and unit cells containing rare earth elements smaller than the matrix phase will be referred to as small unit cells.

[0083] A unit cell containing MA is a matrix phase. The amount of MA is the largest among the rare earth elements contained in the main region 30a. For example, if the number of atoms of the rare earth elements is N(RE) and the number of atoms of the third element, MA, is N(MA) / N(RE) ≥ 0.6. In other words, the proportion of the atomic concentration of MA among the rare earth elements contained in the main region 30a is 60% or more. In other words, in the main region 30a, the ratio of the atomic concentration of the third element to the sum of the atomic concentrations of the first element, the second element, the third element, and the fourth element is 60% or more.

[0084] The critical current densities obtained when magnetic fields of 0.5T, 2.0T, 3.0T, and 5.0T are applied to the oxide superconducting layer 30 in the direction from the first surface F1 to the second surface F2 at a temperature of 77K are given by α (MA / cm²). ２ ), β(MA / cm ２ ), γ (MA / cm ２ ), and δ(MA / cm ２ ) is defined as follows. In this case, at least one inequality holds, for example, α / β > 4.0, α / γ > 10, or α / δ > 70.

[0085] Furthermore, for example, all of the inequalities α / β > 4.0, α / γ > 10, and α / δ > 70 hold true.

[0086] Furthermore, at least one inequality holds, for example, α / β > 6.0, α / γ > 20, or α / δ > 200.

[0087] Furthermore, for example, all of the inequalities α / β > 6.0, α / γ > 20, and α / δ > 200 hold true.

[0088] Furthermore, at least one inequality holds, for example, α / β > 10, α / γ > 40, or α / δ > 1000.

[0089] Furthermore, for example, all inequalities such as α / β > 10, α / γ > 40, and α / δ > 1000 hold true.

[0090] Figures 4(a) and 4(b) are transmission electron microscope (TEM) images of the oxide superconducting layer of the first embodiment. Figures 4(a) and 4(b) are Planview TEM images of the second surface F2 of the oxide superconducting layer 30. Figure 4(b) is an enlarged view of the area enclosed by the frame in Figure 4(a).

[0091] In Figures 4(a) and 4(b), the main region 30a and the sub-region 30b are observed. The sub-region 30b is located between two adjacent main regions 30a.

[0092] Next, a method for manufacturing an oxide superconductor according to the first embodiment will be described.

[0093] The first embodiment of the method for manufacturing an oxide superconductor involves preparing a coating solution using a rare earth element acetate, barium (Ba) acetate, copper (Cu) acetate, and trifluoroacetic acid, applying or injecting the coating solution onto a substrate to form a gel film, performing calcination of the gel film at a temperature of 400°C or lower to form a calcined film, and then performing oxygen annealing of the calcined film under a humidified atmosphere at a temperature of 725°C to 800°C to form an oxide superconducting layer. For example, barium acetate hydrate is used as the barium (Ba) acetate.

[0094] Furthermore, for example, the acetates of rare earth elements, barium (Ba) acetate, and copper (Cu) acetate are all in a crystalline state, and the total amount of impurities in the acetates of rare earth elements, barium (Ba) acetate, and copper (Cu) acetate is 1.10 mol% or less.

[0095] The first embodiment of the method for manufacturing the oxide superconductor 100 involves forming an intermediate layer 20 on a substrate 10, forming an oxide superconducting layer 30 on the intermediate layer 20, and forming a metal layer 40 on the oxide superconducting layer 30. The oxide superconducting layer 30 is formed by the TFA-MOD method.

[0096] Figure 5 is a flowchart showing an example of the preparation of a coating solution for the manufacturing method of an oxide superconductor according to the first embodiment. The following explanation will be given using the case where the first element PA is praseodymium (Pr), the second element SA is samarium (Sm), the third element MA is yttrium (Y), and the fourth element CA is thulium (Lu) as an example.

[0097] As shown in Figure 5, prepare the acetates of yttrium, praseodymium, samarium, lutetium, barium, and copper (a1). Also prepare trifluoroacetic acid (a2). Next, dissolve the prepared metal acetates in water (b) and mix with the prepared trifluoroacetic acid (c). React and purify the resulting solution (d) to obtain a first gel containing impurities (e). Then, dissolve the obtained first gel in methanol (f) to prepare a solution containing impurities (g). React and purify the obtained solution to remove impurities (h) to obtain a second gel containing a solvent (i). Furthermore, dissolve the obtained second gel in methanol (j) to prepare a coating solution (k).

[0098] Mix the metal acetates so that RE(Y,Pr,Sm,Lu):Ba:Cu = 1:2:3. Mix so that the amount of Pr in the RE site is between 0.00000001 and 0.20. After mixing and reaction, the amount of residual water and acetic acid in the coating solution is reduced to 2 wt% or less by a high-purity solution purification process using the SIG (Stableized Sovent-Into-Gel) method. The SIG method in the first embodiment is a high-purity solution purification method that partially stabilizes the solution to prevent the decomposition of PrBCO, and is the PS-SIG (Partially Stabilized Sovent-Into-Gel) method.

[0099] Barium acetate hydrate is used as the acetate of barium (Ba). For example, barium acetate hydrate is (CH₂). ３COO) ２ Ba・H ２ It is represented by the chemical formula O. Barium acetate hydrate is in a crystalline state.

[0100] Furthermore, the yttrium acetate, praseodymium acetate, samarium acetate, lutetium acetate, barium acetate, and copper acetate are all in a crystalline state, and the total amount of impurities in the yttrium acetate, praseodymium acetate, samarium acetate, lutetium acetate, barium acetate, and copper acetate is, for example, 1.10 mol% or less.

[0101] Figure 6 is a flowchart showing an example of a method for forming a superconductor film from a coating solution in the manufacturing method of an oxide superconductor according to the first embodiment.

[0102] As shown in Figure 6, first, the previously prepared coating solution is prepared (a). The coating solution is applied to the substrate, for example, by die coating, to form a film (b) and obtain a gel film (c). Then, the obtained gel film is subjected to a primary heat treatment called calcination to decompose organic matter (d) and obtain a calcined film (e). Furthermore, this calcined film is subjected to a secondary heat treatment called final calcination (f), and then, for example, pure oxygen annealing is performed (h) to obtain a superconducting film (h).

[0103] Figure 7 shows a typical calcination profile for the manufacturing method of an oxide superconductor according to the first embodiment. The calcination temperature is, for example, 400°C or lower. In calcination under atmospheric pressure, trifluoroacetate is mainly decomposed between 200°C and 250°C. To prevent exceeding that temperature range, the heating rate is reduced around 200°C. With a gradual heating to 250°C, the substances decomposed from trifluoroacetate contain fluorine and oxygen, and these fluorine and oxygen tend to remain in the film due to hydrogen bonding. To remove these substances, the temperature is raised to 400°C. In this way, a translucent brown calcined film composed of oxides and fluorides is obtained.

[0104] Figure 8 shows a typical calcination profile for the manufacturing method of the oxide superconductor according to the first embodiment. The calcination is performed at a temperature of, for example, 725°C to 800°C.

[0105] Up to tb1 at 100°C, the mixture is dry, but humidification is performed from there. The humidification start temperature can be between 100°C and 400°C. The formation of the pseudo-liquid layer is thought to begin around 550°C, so humidification is performed at a temperature below that to ensure that the humidified gas spreads throughout the membrane and a uniform pseudo-liquid layer is formed.

[0106] Figure 8 shows a typical temperature profile for the 800°C firing. The heating profile is gradual from 775°C to 800°C to avoid temperature overshoot at tb3. Even with this, an overshoot of 2-3°C may remain at 800°C, but this is not a significant problem. The oxygen partial pressure at the maximum temperature depends on the matrix phase. In the case of YBCO superconductor firing, it is 1000 ppm at 800°C, and the optimal oxygen partial pressure is halved for every 25°C decrease in temperature. That is, it is 500 ppm at 775°C and 250 ppm at 750°C. In this firing, for YBCO systems, YBa... ２ Cu ３ O ６ A superconductor is formed. At this point, it is not a superconductor.

[0107] During the final firing at the highest temperature, a drying gas is introduced at tb4 before the firing is complete and the temperature begins to decrease. This is because humidifying gas decomposes the superconductor into oxides below 700°C. Oxygen annealing is performed at tb6 to increase the oxygen count of the superconductor from 6.00 to 6.93. At this oxygen count, it becomes a superconductor. However, PrBCO is the only one that has a perovskite structure but is not a superconductor. Also, since the valence of Pr is unknown, the oxygen count in the unit cell is also unknown, but it is thought to be high. This is because the valence of Pr takes a value between 3 and 4, and the number of oxygen atoms in the unit cell increases accordingly. The temperature for oxygen annealing is, for example, between 375°C and 525°C. After the temperature holding period ends, furnace cooling is performed from tb8.

[0108] By the above manufacturing method, an oxide superconductor 100 of the first embodiment, including an oxide superconducting layer 30, is manufactured.

[0109] Next, the operation and effects of the oxide superconductor 100 of the first embodiment will be described.

[0110] The oxide superconductor 100 of the first embodiment includes a matrix phase of YBCO in the oxide superconducting layer 30. Non-superconductor PrBCO is clustered in the matrix phase together with the superconductors SmBCO and TmBCO. These clusters function as atomic-level artificial pins, improving the magnetic field properties of the oxide superconductor 100.

[0111] The oxide superconducting layer 30 of the first embodiment consists of PA, SA, MA, and CA. SA and CA induce a clustering phenomenon. PA is incorporated into the cluster as part of SA, forming clustered atom-replaced artificial pins (CARPs). These clustered atom-replaced artificial pins improve the magnetic field characteristics.

[0112] Furthermore, in the first embodiment, the oxide superconductor 100 includes a main region 30a and a sub-region 30b in the oxide superconducting layer 30. The volume ratio of the sub-region 30b to the oxide superconducting layer 30 is 1.10% or less. By having a volume ratio of 1.10% or less of the sub-region 30b to the oxide superconducting layer 30, the magnetic field characteristics of the oxide superconductor 100 can be improved by CARP.

[0113] Furthermore, according to the manufacturing method of the oxide superconductor 100 of the first embodiment, by using high-purity barium acetate hydrate as the barium (Ba) acetate, it is possible to manufacture an oxide superconductor 100 with improved magnetic field characteristics.

[0114] The realization of CARP was expected to enable superconductivity applications at low temperatures and low magnetic fields. However, CARP does not always fully demonstrate its function of improving magnetic field characteristics. The reason for this is thought to be the non-superconducting regions that do not possess superconducting properties, formed along the low-angle grain boundaries near the surface of the oxide superconducting layer. These non-superconducting regions formed along the low-angle grain boundaries are, for example, amorphous. The non-superconducting regions formed along the low-angle grain boundaries near the surface correspond to the sub-region 30b of the oxide superconducting layer 30 in the first embodiment.

[0115] In the current research stage, CARP primarily involves inserting only 8% of the material that will become the CARP element into the rare earth element sites. In other words, if the quantum magnetic flux is in a position to pass through one CARP, a pinning force acts that reduces the 8% superconducting potential.

[0116] In the oxide superconducting layer 30 produced by the TFA-MOD method, a sub-region 30b, which is a non-superconducting region, is formed along the low-angle grain boundary 30x. The sub-region 30b is thought to be caused, for example, by impurities in the solution used when forming the oxide superconducting layer 30.

[0117] Hereinafter, the main region 30a may be referred to as the superconducting region, and the sub-region 30b as the amorphous region.

[0118] The oxide superconducting layer 30 includes, for example, multiple main regions 30a measuring 50 nm × 200 nm. The main regions 30a are aggregates of unit cells. Amorphous regions, which are sub-regions 30b, are formed in the oxide superconducting layer 30.

[0119] Let's assume that 1% of impurities are present in the solution, and that these impurities create amorphous regions. In this case, an amorphous region with a width of 10% (5 nm) and a thickness of 10% (22 nm for a 220 nm superconductor) may be formed in the main region 30a of 50 nm x 200 nm. Since a 10% pinning force acts on the amorphous region with a thickness of 10%, the quantum magnetic flux of 5 nmΦ at 30 K enters the amorphous region.

[0120] The amorphous region described above, with a width of 5 nm, can be made, for example, 200 nm long. For example, within a length of 200 nm, another quantum magnetic flux enters the region at a position where the repulsive force of the existing quantum magnetic flux does not reach, moves in one direction, and pushes the other quantum magnetic flux. The pushed quantum magnetic flux exceeds the pinning force at its end and enters the superconducting region from the amorphous region. In this way, the magnetic field properties of the superconductor are reduced.

[0121] As with the amorphous region described above, we will refer to the pathway through which multiple quantum magnetic fluxes gather and move as a quantum flux gallery (QFG). We believe that reducing this QFG is the key to the effectiveness of CARP.

[0122] In the first embodiment, a structure with reduced QFG is realized, providing a structure that can exert the effects of CARP. In the first embodiment, the manufacturing method for the structure with reduced QFG is also described, along with the reason why the QFG is reduced by the manufacturing method. Furthermore, a method for detecting the structure with reduced QFG is also described.

[0123] CARP is a structure that can only be fabricated using the TFA-MOD method, which forms unit cells through liquid phase growth. When CARP is fabricated using the TFA-MOD method, for example, numerous superconducting regions with a size of 50 nm x 200 nm are formed, and amorphous regions are formed if there are foreign materials. These foreign materials form, for example, QFGs with a length of 200 nm or 50 nm. The presence of QFGs allows the penetration of multiple quantum magnetic fluxes, leading to a decrease in magnetic field properties.

[0124] In other words, the QFG needs to be sufficiently small for CARP to function. Furthermore, at 30K (quantum magnetic flux of 5 nmΦ), a 4 nm wide QFG also degrades the magnetic field characteristics. This is because, if a 4 nm wide and 50 nm long QFG exists, and the center of the 5 nmΦ quantum magnetic flux is located at the center of the QFG, most of the quantum magnetic flux enters the 4 nm wide non-superconducting region, thus reducing the superconducting potential. Since the rate of reduction in the superconducting potential is determined by the occupied area, the reduction rate is over 90%. Because the superconducting potential is reduced by 90%, quantum magnetic flux accumulates in the QFG in this case as well.

[0125] The following explains the causes of QFG formation, methods for reducing QFG, and the structures in which CARP can be effective.

[0126] In the formation of CARP, impurities in the raw material acetate affect its formation. Patents No. 7330152 and No. 7330153 use acetate with a purity of 98% or 99%, according to the vendor's description.

[0127] However, a 99% pure acetate contains 1% impurities, which is thought to lead to the formation of QFGs and prevent CARP from being effective. Therefore, it is considered necessary to form CARP using a crystalline raw material with impurities at the 0.1% level.

[0128] For example, copper acetate used in the formation of CARP is a transparent blue monohydrate crystal, while yttrium acetate is a transparent tetrahydrate crystal. The amount of impurities in acetates of elements such as Pr, Sm, and Tm that form CARP can also be reduced by using crystals that have hydrates.

[0129] Among the acetate salts used in the formation of CARP, barium acetate is the only one for which a salt containing crystal water is not commercially available. This was the situation in Japan at least as of 2024. Barium acetate is purchased in the form of white pellets or powder. The white part of barium acetate is barium carbonate formed by the absorption of carbon dioxide from the atmosphere. Barium carbonate is known as a stable and difficult-to-decompose substance in the superconductivity manufacturing process. The TFA-MOD method itself has developed through methods that avoid barium carbonate formation.

[0130] In the first embodiment, the aim was to reduce the amount of impurities and QFG (Quick Fibre Grain) in the formation of CARP by the TFA-MOD method by using crystalline barium acetate monohydrate. Barium acetate monohydrate is a transparent rod-shaped crystal and is stable in a dry atmosphere at room temperature. The use of crystalline barium acetate monohydrate reduces the amount of QFG, allowing the CARP's inherent effect of improving its properties in a magnetic field to be exhibited.

[0131] Before describing the details of the operation and effects of the first embodiment, a basic scientific explanation of artificial pins will be given.

[0132] Regarding artificial pins, several phenomena are understood through empirical observation. For example, an artificial pin that is effective at 30K may not be effective at 77K, and an artificial pin that is effective at 77K may not be effective at 30K. However, I believe there are probably no papers or explanatory books that clearly explain the above decrease.

[0133] As mentioned above, there are no papers or explanations that clearly demonstrate the phenomenon related to artificial pins. Therefore, I will not explain artificial pins in detail here in a way that can be understood by non-experts.

[0134] In short, an artificial pin is a device that pins down the quantum magnetic flux, which is the source of the magnetic field that degrades superconductivity, thereby mitigating the degradation of superconductivity. The pinning of quantum magnetic flux is achieved by utilizing the difference in superconducting potential over a certain distance. Therefore, any non-superconducting material will exhibit the pinning effect. In other words, it has the effect of mitigating the degradation of superconductivity in a magnetic field.

[0135] Assuming the superconducting potential of the superconducting state is 100% and the superconducting potential of the non-superconducting region is 0%, energy is required to move the quantum magnetic flux from 100% potential to 0%, or vice versa. The rate of change of potential when the quantum magnetic flux is moved a certain distance is the pinning force that makes it difficult for the quantum magnetic flux to move.

[0136] For example, if the travel distance is 5 nm and the superconducting potential changes from 0% to 100%, a stress corresponding to this change is applied to the quantum magnetic flux, making it difficult for the quantum magnetic flux to move within the superconductor. For example, if the travel distance is 50 nm and the potential changes from 0% to 100%, the rate of change of the potential is 0.1 times that of the case where the travel distance is 5 nm, so the pinning force also becomes smaller.

[0137] Furthermore, even with a displacement of 5 nm, if the potential changes from 0% to 20%, the pinning force will still decrease, and the pinning force will be only 0.2 times that of when the potential changes from 0% to 100%.

[0138] It appears that the ease with which quantum magnetic flux moves varies with temperature. However, at least at the same temperature, the thermal disturbance of quantum magnetic flux is the same, making it possible to compare the magnitude of the pinning force.

[0139] The size of the quantum magnetic flux, which is deeply involved in pinning, is related to the critical temperature T of the material. ｃ It is said to depend on the type. The size of the quantum magnetic flux is said to be around the coherence length. YBa ２ Cu ３ O ６．９３ In superconductors, the quantum magnetic flux is said to be 5 nmΦ at 30 K and 50 nmΦ at 77 K.

[0140] Some quantum magnetic fluxes can cause the superconducting state to collapse when they penetrate into a superconductor. However, in the case of YBa ２ Cu ３ O ６．９３ they can coexist in the superconductor. However, when the quantum magnetic flux moves inside, the region of the superconducting state becomes smaller and the superconducting properties deteriorate. Therefore, it is important to make the quantum magnetic flux difficult to move in order to prevent the deterioration of the superconducting properties. The sites that make the quantum magnetic flux difficult to move are artificial pins.

[0141] Here, the superconductor BS-SC1 (basic science, superconductor 1) is made entirely of a superconductor, and a critical current density J ｃ is obtained at 30 K. The superconducting properties of this superconductor BS-SC1 are defined as 100%. The superconductor BS-SC1 has a uniform interior, and in the magnetic field BS-B1 (basic science, magnetic field B1), the quantum magnetic flux moves inside and the superconducting properties are reduced to 10%.

[0142] The superconductor BS-SC2 is assumed to have 10% by volume of a non-superconducting part, that is, artificial pins, which match the quantum magnetic flux size of 5 nmΦ at 30 K, with the superconductor of BS-SC1. Since 10% of the superconductor BS-SC2 is non-superconducting, a Jc value of 90% can be obtained at 30 K.

[0143] When BS-SC2 is moved into the magnetic field B1, the quantum magnetic flux is successively captured by the artificial pins with a volume of 10%, and a large amount of quantum magnetic flux that cannot move is generated. Therefore, the deterioration of the superconducting properties is alleviated, and superconducting properties of 30% can be obtained. This is the function of the artificial pins.

[0144] When asked what an artificial pin is, it does not improve the superconducting properties, but alleviates the deterioration of the superconducting properties in a magnetic field. When using BS-SC1 and BS-SC2 in the magnetic field B1, BS-SC2 obtains a current value three times that of BS-SC1. This is not because the superconducting properties have improved, but because the influence of the quantum magnetic flux is alleviated, and only a larger J ｃ value can be achieved than that of BS-SC1.

[0145] In other words, artificial pins can never exceed their inherent maximum performance of 100%. Realistically, it is also virtually impossible to achieve 100% superconductivity in a magnetic field. This would require all quantum magnetic flux to be completely pinned to the artificial pin, resulting in zero influence, which is an unrealistic condition.

[0146] In relation to the above explanation, there is a phenomenon called the matching magnetic field phenomenon. The matching magnetic field phenomenon is a phenomenon in which the superconducting properties of a superconductor become higher when a magnetic field is applied than when there is no magnetic field. The matching magnetic field phenomenon is thought to occur because a ferromagnetic material that creates a magnetic field is present inside the superconductor.

[0147] For example, suppose a ferromagnetic material is present inside a superconducting material, and a magnetic field of 0.1 T is applied to a neighboring superconducting material. In this case, even with an externally applied magnetic field of 0.0 T, the superconducting material will exhibit the same low superconductivity as if an external magnetic field of 0.1 T were applied. If an external magnetic field is applied to the superconducting material in such a way that the internal 0.1 T magnetic field is canceled out, the superconductivity will effectively become 0.0 T, making it appear as if the superconductivity has improved. For example, the degree of improvement in superconductivity can reach three times.

[0148] One thing to be aware of in the matching magnetic field phenomenon is that the ferromagnetic material providing the magnetic field effectively reduces the superconducting properties both physically and electrically. For example, in a superconductor with the above-mentioned ferromagnetic material inside, if we define the superconducting properties at 0.0 T as 100% when the ferromagnetic material is not present, then in this case, the superconducting properties might be as low as 15% because the magnetic field created by the ferromagnetic material and the ferromagnetic material blocking the superconductor network.

[0149] Suppose that when a magnetic field of 0.1 T is applied to the superconductor, and the internal magnetic field becomes virtually zero, the superconducting properties become 45%. In this case, since the properties have improved threefold despite the application of a 0.1 T magnetic field, it appears as though the superconducting properties have improved by utilizing the matching magnetic field.

[0150] However, the original 100% superconducting property means that the maximum value decreases to 45% due to the influence of the ferromagnetic material, and the highest property itself of 100% does not increase. Also, in principle, it is impossible to exceed the highest property that a superconductor has. Here, the highest property refers not to the highest property that can be calculated in theoretical physics and the like, but to the highest property measured in a superconducting film having appropriately low-angle grain boundaries. It is the superconducting property obtained when the influence of a small self-magnetic field can be excluded by natural pins, rather than the superconducting property of a bulk superconductor.

[0151] There is no example where the 100% J value of the superconductor becomes higher under the same temperature conditions. Also, considering the above physical and magnetic field phenomena related to artificial pins, there is no reason for the 100% J value of the superconductor to become higher under the same temperature conditions. ｃ There is no example where the 100% J value of the superconductor becomes higher under the same temperature conditions. Also, considering the above physical and magnetic field phenomena related to artificial pins, there is no reason for the 100% J value of the superconductor to become higher under the same temperature conditions. ｃ There is no example where the 100% J value of the superconductor becomes higher under the same temperature conditions. Also, considering the above physical and magnetic field phenomena related to artificial pins, there is no reason for the 100% J value of the superconductor to become higher under the same temperature conditions.

[0152] Next, it is explained that artificial pins effective at 30 K are effective only at 30 K, and artificial pins effective at 77 K are effective only at 77 K. This is the case of a YBaCuO superconductor. It is also added here that there is little difference in the discussion even if yttrium (Y) is replaced by other rare earth elements (Re). ２ Cu ３ O5] ６．９３ There is little difference in the discussion even if yttrium (Y) is replaced by other rare earth elements (Re).

[0153] T ｃ At the T value, the coherence length diverges to infinity, but the maximum T that can be used in practice is possessed by SmBaCuO which is considered to be superconducting. The T is 94.0 K, and there is only a difference of 3.3 K from the YBaCuO superconductor. ｃ SmBa ２ Cu ３ O ６．９３ T ｃ is 94.0 K, and there is only a difference of 3.3 K from the YBaCuO superconductor. ２ Cu ３ O ６．９３ At the T value, the coherence length diverges to infinity, but the maximum T that can be used in practice is possessed by SmBaCuO which is considered to be superconducting. The T is 94.0 K, and there is only a difference of 3.3 K from the YBaCuO superconductor.

[0154] Re entering the Y site has a smaller ionic radius as the atomic number increases due to the lanthanoid contraction, and the T value becomes smaller. Even for Lu with the smallest ionic radius, the T value is 87 - 88 K. Superconductors with a low T are not realistically used, and Eu, Ho, Gd, etc. are used. ｃ Lu ｃ value is 87 - 88 K. ｃ Superconductors with a low T are not realistically used, and Eu, Ho, Gd, etc. are used. ｃThe values ​​range from 90.7 to 94.0K, with a small difference. At least when discussing 30K and 77K, there is no significant impact.

[0155] Figure 9 is an explanatory diagram of the operation and effects of the oxide superconductor of the first embodiment. Figure 9 is a schematic diagram of the YBCO superconductor viewed from above.

[0156] The rectangle represents an artificial pin measuring 5 nm x 5 nm. The artificial pin is a non-superconductor with zero internal superconducting potential. Figure 9 shows artificial pin P5-1 (Pinning center 5 nm, No. 1) and artificial pin P5-2.

[0157] The circles represent quantum magnetic flux. Figure 9 shows the case of a YBCO superconductor, and since it is cooled to 30K, the quantum magnetic flux has a diameter of 5 nmΦ. Figure 9 shows quantum magnetic fluxes B5-1, B5-2, and B5-3.

[0158] Figure 9 shows the state in which the quantum magnetic flux B5-1 enters the artificial pin P5-1. For example, when the quantum magnetic flux B5-1 leaves the artificial pin P5-1, the quantum magnetic flux B5-1 moves 5 nm, and the superconducting potential changes from 0% to 100%. As a result, the quantum magnetic flux B5-1 is subjected to a pinning force, which is a stress corresponding to the change in its superconducting potential.

[0159] In Figure 9, quantum magnetic flux B5-2 is pinned to artificial pin P5-2. For example, suppose another quantum magnetic flux B5-3 approaches quantum magnetic flux B5-2. Although there is a repulsive force between quantum magnetic fluxes, quantum magnetic flux B5-2 is pinned to artificial pin P5-2 and therefore does not move even when subjected to stress from quantum magnetic flux B5-3. On the other hand, quantum magnetic flux B5-3 will experience a repulsive force from quantum magnetic flux B5-2, causing its trajectory to curve.

[0160] In this case, the quantum magnetic flux B5-2 will remain pinned to the artificial pin P5-2, thus improving the magnetic field characteristics. If there are many artificial pins, the quantum magnetic flux B5-3 will also be pinned. If the quantum magnetic flux and the artificial pins are the same size (5 nmΦ), the superconductivity in the magnetic field will improve.

[0161] Figure 10 is an explanatory diagram of the operation and effects of the oxide superconductor of the first embodiment. Figure 10 is a schematic diagram of the YBCO superconductor viewed from above.

[0162] Next, using Figure 10, we will explain whether the 5 nmΦ artificial pin, which showed effectiveness at 30 K in Figure 9, is also effective at 77 K.

[0163] Figure 10 shows artificial pins P5-4, P5-5, P5-6, and P5-7, each measuring 5 nm x 5 nm. YBa ２ Cu ３ O ６．９３ Since the superconductor is at 77K, the size of the quantum magnetic flux is 50 nmΦ. Quantum magnetic flux B50-1 represents a quantum magnetic flux of 50 nmΦ.

[0164] In Figure 10, when quantum magnetic flux B50-1 is at B50-1a, quantum magnetic flux B50-1 has no artificial pins inside, and its superconducting potential is 100%. When quantum magnetic flux B50-1 moves to position B50-1b, it has artificial pins P5-4 and P5-5 measuring 5 nm × 5 nm inside, and its superconducting potential becomes 98%. For simplicity, here we treat 5 nm × 5 nm and 5 nmΦ as having the same area and explain it as 1 / 100 of the 50 nm × 50 nm region.

[0165] When quantum magnetic flux B50-1 moves to position B50-1c, it has artificial pins P5-5, P5-6, and P5-7 inside, so its superconducting potential is 97%. Quantum magnetic flux B50-1a moves 25 nm at a time, and its superconducting potential changes from 100% to 98% and then to 97%. The rate of change of the superconducting potential is -2% / 25 nm and -1% / 25 nm, indicating that the pinning force is almost nonexistent for quantum magnetic flux B50-1a.

[0166] Since 5nm x 5nm artificial pins are uniformly dispersed, the probability of a large number of artificial pins being concentrated in one place is small. For example, the probability of 30 artificial pins being placed in a 50nmΦ region is astronomically low. Furthermore, even if 30 artificial pins are placed in a 50nmΦ region, the superconducting potential only changes from 100% to 70%. Compared to the case where 50nmΦ artificial pins are present, as will be explained next, the pinning force is almost negligible.

[0167] Figure 11 is an explanatory diagram of the operation and effects of the oxide superconductor of the first embodiment. Figure 11 is a schematic diagram of the YBCO superconductor viewed from above.

[0168] Next, we will explain the case where artificial pins and quantum magnetic flux of the same size exist at 77K using Figure 11. Figure 11 shows a superconductor having artificial pins P50-2 of 50 nm × 50 nm cooled to 77K. The quantum magnetic flux B50-2 is 50 nmΦ at 77K.

[0169] For example, the quantum magnetic flux B50-2 moves from position 50-2a to 50-2b and 50-2c. When the quantum magnetic flux B50-2 moves by 50 nm, the superconducting potential changes from 0% to 100%.

[0170] In the case of Figure 10, no pinning force was exerted due to the artificial pins having different quantum magnetic flux sizes. However, as shown in Figure 11, a large pinning force is exerted when the size of the artificial pins matches the size of the quantum magnetic flux. However, there is one point to note here. At 77K, the quantum magnetic flux moves 50 nm for the superconducting potential to change from 0% to 100%. At 30K, it moves 5 nm for the superconducting potential to change from 0% to 100%. At 77K, the pinning force is only 1 / 10 of that at 30K.

[0171] The above comparison is not straightforward because the temperatures are different at 30K and 77K. However, generally speaking, thermal disturbances are greater at higher temperatures, and quantum magnetic flux pinning at 77K is probably difficult. The pinning force due to distance is reduced to 1 / 10, and the effect of thermal disturbances further reduces the pinning force, so the pinning effect is probably only 1 / 50 or 1 / 100 of that at 30K.

[0172] Another point of interest is the number of artificial pins. YBa ２ Cu ３ O ６．９３ Regardless of whether it's a superconductor or not, it's impossible to insert an infinite number of artificial pins. If you insert artificial pins that make up 50% of the volume, YBa ２ Cu ３ O ６．９３ The volume proportion of the superconducting region within a superconductor is 50%. Therefore, the continuity of the superconducting region in the superconductor is interrupted, and the superconducting properties of the superconductor decrease. Furthermore, if the artificial pin is made of low-strength amorphous material, the physical strength of the superconductor will be insufficient.

[0173] The extent to which artificial pins can be incorporated into superconductors by volume has been studied in the past. While some reports indicate a maximum volume percentage of 30%, it is generally believed that around 15% is the limit from the perspective of maintaining the strength of the superconductor. In actual applications, artificial pins in superconductors that are stably used are said to occupy around 15% of the volume.

[0174] When discussing the number of artificial pins for 30K and 77K, the shape of the artificial pins becomes important. Is the artificial pin spherical (3D) or cylindrical (2D)? Here, we will assume a cylindrical, 2D artificial pin with a small difference in length relative to its radius.

[0175] The artificial pin sizes for 30K and 77K are 5nmΦ and 50nmΦ, respectively. As mentioned above, artificial pins occupy only 15% of the volume. Suppose we have a superconductor with 1,000 5nmΦ artificial pins for 30K. If we were to change the artificial pins to 50nmΦ, which are effective at 77K, while maintaining the same volume as the superconductor, the number of artificial pins would be reduced to 10. At 77K, where the quantum magnetic flux is large, the number of artificial pins cannot be increased, and the effect becomes less than 1 / 100th of that at 30K.

[0176] As mentioned above, the pinning effect at 77K is 1 / 100th of that at 30K in terms of volume, but when thermal disturbances are also taken into account, it is thought to be 1 / 1000th of that at 30K. Therefore, it is unlikely that a large pinning effect can be obtained at 77K.

[0177] As will be explained later, the ideal structure at 77K is that of a 2G superconducting wire. This is because it has artificial pins with a diameter of 50 nm, and the superconducting potential changes from 0% to 100%. This is an ideal configuration of artificial pins, and it is considered that nothing better can be theoretically created. The explanation for this will be given later.

[0178] Figure 12 is an explanatory diagram of the operation and effects of the oxide superconductor of the first embodiment. Figure 12 is a schematic diagram of the YBCO superconductor viewed from above.

[0179] Next, we will explain, using Figure 12, whether there is an improvement in magnetic field characteristics when a superconductor with a 50 nmΦ artificial pin for 77 K is cooled to 30 K. As shown in Figure 12, let's assume that there is an artificial pin P50-2 of 50 nm × 50 nm. Let's assume that the quantum magnetic flux B5-8 at 30 K approaches the artificial pin P50-2, enters its interior, and moves to the boundary between the artificial pin P50-2 and the superconductor due to stress. Since the superconducting potential is 0% everywhere inside the superconductor, no pinning force acts, and the quantum magnetic flux can move freely.

[0180] At the interface between the artificial pin and the superconductor, a 5 nm diameter quantum magnetic flux B5-8 moves 5 nm, causing the superconducting potential to change from 0% to 100%, which might suggest that the quantum magnetic flux cannot move. However, because quantum magnetic flux B5-8 is much smaller than the artificial pin P50-2, other quantum magnetic fluxes B5-9 and B5-10 penetrate the artificial pin. This is because the repulsive force of B5-8 cannot reach them. As a result, quantum magnetic fluxes B5-9 and B5-10 move in the same direction and exert a repulsive force on each other.

[0181] Even if quantum magnetic fluxes B5-9 and B5-10 are fortunate enough to exist alongside quantum magnetic flux B5-8 near the interface, in that case, the repulsive force will no longer act at the entrance of the quantum magnetic flux, allowing yet another quantum magnetic flux to penetrate.

[0182] In this way, a repulsive force is finally exerted on quantum magnetic flux B5-8 by other quantum magnetic fluxes, exceeding the pinning force and penetrating from the artificial pin into the superconductor. In other words, an artificial pin that is too large has no effect on a small quantum magnetic flux.

[0183] Until now, in the world of superconductivity, there has been no literature that rationally explains why artificial pins that are effective at 30K and 77K are ineffective at the opposite temperatures. However, as mentioned above, from the perspective of physical phenomena dealing with magnetic fields, the artificial pins that are effective at 30K and 77K have completely different sizes, 5 nmΦ and 50 nmΦ, respectively. Therefore, it can be understood that one is ineffective against the other. Thus, it is thought that a structure with artificial pins that are effective across the entire temperature range, including 30K and 77K, cannot exist.

[0184] Let's assume we can create artificial pins that are effective at both 30K and 77K. The maximum amount of artificial pins is 15%, and even if 7.5% of them are 5nmΦ artificial pins that are effective at 30K, the effect of the artificial pins will be half that of 15%. Furthermore, if they are effective at 77K, then 50nmΦ artificial pins must also be present. In other words, a structure containing two types of artificial pins, 5nmΦ and 50nmΦ, is required.

[0185] Next, we will explain why PLMP is heterogeneous and unstable. ReBa ２ Cu ３ O ７－ｘ Superconductors exhibit superconducting properties when rare earth elements such as yttrium (Y) are present in rare earth sites (Re). It is known that the best superconducting properties are obtained when x = 0.07, or when the oxygen number is 6.93. It has long been known that non-superconductors occur at oxygen numbers of 6.00 (x = 1.00) and 7.00 (x = 0.00).

[0186] ReBa ２ Cu ３ O ７－ｘ The superconducting properties of superconductors are sensitive to the oxygen number, and the properties deteriorate significantly at both 6.80 and 6.70 oxygen numbers. This is thought to have a major impact on PLMP, which will be discussed later. Also, when the properties deteriorate due to a change in the oxygen number, the T ｃ It is also widely known that this can decrease.

[0187] For example, YBa ２ Cu ３ O ７－ｘIn superconductors, the highest J is achieved when the oxygen number is 6.93. ｃ It is assumed that a value can be obtained. In this case, T ｃ The value is 90.7K. ｃ This is not the highest value. In bulk superconductors, J ｃ The value is about 1 / 100th of that of a thin-film superconductor, ｃ The value improves to 92-93K. This is because there are no naturally formed artificial pins inside the bulk superconductor. ｃ This is thought to be because the value drops significantly. On the other hand, in thin-film superconductors, low-angle grain boundaries exist inside, and these low-angle grain boundaries act as artificial pins, T ｃ Although the magnetic field strength decreases, it is believed that high superconductivity is achieved because the influence of the tiny magnetic field created by the superconducting current is reduced.

[0188] Thin-film superconductors using NLMP, PLMP, and SLMP all exhibit good J characteristics. ｃ A value has been obtained. Good J ｃ The value is 77K, 0T, and 1MA / cm ２ This refers to the superconducting properties described above. This is the 0.01 MA / cm² of bulk superconductors. ２ This characteristic far surpasses the superconducting properties of the preceding and succeeding elements.

[0189] If the number of oxygen atoms changes, and the number of oxygen atoms deviates from the optimal value of 6.93, then in the case of a thin-film superconductor, T ｃ The value changes towards the smaller side. ｃ The value depends on the type of rare earth element (Re), so here we use YBa. ２ Cu ３ O ７－ｘ Let's compare using superconductors. YBa ２ Cu ３ O ７－ｘ In superconductors, when the number of oxygen atoms is 6.93, the J ｃ The value reaches its maximum, and at that time T ｃ The value is said to be 90.7K.

[0190] As mentioned above, a oxygen number of 7.00 is not superconducting, but the same applies to 6.80 and 6.70 J. ｃ The value decreased significantly, and at the same time, T ｃThe value also drops significantly. ｃ Since the value is measured through all superconductors during measurement, the decrease in oxygen number and T ｃ It is difficult to determine the exact numerical value of the decrease. When the oxygen count decreases, T ｃ The values ​​were 89K and 87K, and when they dropped significantly, results of 85K and 82K were also observed. At least when the oxygen count changes from the optimal value, T ｃ The price will fall.

[0191] T ｃ Samples with low values ​​have T inside. ｃ There is always a point where the value is low. YBa ２ Cu ３ O ７－ｘ If a superconductor is formed and only the number of oxygen atoms differs, then if the number of oxygen atoms decreases from 6.93 to 6.80 or 6.70, then J ｃ The value decreases from 100% to, for example, 30% or 10%. One of the points where the current passes is T. ｃ This is because it becomes a normal conductor.

[0192] For the sake of clarity, the discussion of oxygen number reduction in this specification is based on YBa. ２ Cu ３ O ７－ｘ Based on the concept of superconductors, we will explain the superconductivity characteristics when the oxygen number is 6.93, 6.80, and 6.70, using 100%, 30%, and 10% respectively. These values ​​are not precise experimental values, and measuring them is extremely difficult. However, the actual characteristics are thought to be close to these values.

[0193] The above observations are largely consistent with superconductors using other rare earth elements (Re). For example, GdBa ２ Cu ３ O ７－ｘ Superconductors and SmBa ２ Cu ３ O ７－ｘ Superconductors have a maximum joule count of 6.93 oxygen atoms. ｃ A value is obtained. Maximum J ｃ T when a value is obtained ｃ The values ​​are said to be around 92.5K and 94.0K, respectively. Even if the rare earth elements (Re) are different, if the number of oxygen atoms in the superconductor changes, the T will be the same. ｃ The value decreases Jｃ The value decreases. GdBa ２ Cu ３ O ７－ｘ Superconductors and SmBa ２ Cu ３ O ７－ｘ T in superconductors ｃ The decrease in value is due to each T ｃ This represents a decrease from the maximum values ​​of 92.5K and 94.0K.

[0194] To be clear, the above discussion concerns the GdBa of thin films. ２ Cu ３ O ７－ｘ Superconductors and SmBa ２ Cu ３ O ７－ｘ This is about superconductors. If it's a bulk superconductor, then it's definitely J. ｃ The value decreased to 1 / 100, T ｃ The value will increase by 2-3K compared to the value mentioned above.

[0195] YBa ２ Cu ３ O ７－ｘ As mentioned earlier, if a superconductor has good superconducting properties, then T ｃ = 90.7 K, and the amount of J obtained at that temperature ｃ The value is still zero. When cooled, it will be J ｃ The values ​​improved, and at a liquid nitrogen temperature of 77K, the sample on a single crystal substrate showed a density of 5-7 MA / cm². ２ It is known that the characteristics (77K, 0T) can be obtained.

[0196] YBa ２ Cu ３ O ７－ｘ Superconductors do not improve indefinitely with cooling. In a temperature-dependent study conducted in the US, the superconductor's properties were 70 MA / cm² at 4.2 K, the boiling point of liquid helium. ２ There are reports that characteristics (4.2K, 0T) were obtained.

[0197] In the temperature range from 77K to 4.2K, the lower the temperature, the greater the J. ｃ The value will rise. 20K J ｃ The value is approximately 40 MA / cm ２(20K, 0T). Superconducting properties are a similarly recognized characteristic among materials researchers worldwide. As mentioned earlier, superconducting properties cannot be improved by artificial pins, nor can they be enhanced by matching magnetic field effects. In other words, the highest performance at 20K was 40 MA / cm². ２ Therefore, this is the case with YBCO superconductors, but other ReBa ２ Cu ３ O ７－ｘ It is believed that superconductors also exhibit similar values. While different superconductors, such as Bi-based superconductors, have completely different characteristics, ReBa... ２ Cu ３ O ７－ｘ The characteristics of superconductors at 20-30K are expected to be almost the same.

[0198] As explained above, ReBa ２ Cu ３ O ７－ｘ Even with the presence of artificial pins in the superconductor and the effect of matching magnetic fields, the magnetic field strength remains 40 MA / cm. ２ It will never exceed (20K, 0T). Matching magnetic fields and artificial pins do not improve the characteristics; they only make it appear better by mitigating degradation conditions, and it is impossible from a natural science perspective to exceed the original characteristics.

[0199] Furthermore, when a magnetic field of 1T is applied to a superconductor (20K, 1T), quantum magnetic flux corresponding to the magnetic field penetrates the interior of the superconductor, and its properties degrade to a greater or lesser extent. There have never been any reports of a superconductor exhibiting higher performance at 1T than at 0T, near its inherent maximum performance.

[0200] The above explains the basic physical phenomena related to artificial pins, and ReBa ２ Cu ３ O ７－ｘ This is about the superconducting properties of superconductors. Research since Bednorz and Muller's discovery of high-temperature superconductivity has shown that ReBa ２ Cu ３ O ７－ｘ As of 2024, no superconductor with greater practical applications than conventional superconductors has been discovered.

[0201] Next, we will explain NLMP and PLMP in order. ReBa ２Cu ３ O ７－ｘ Regarding superconductors, two main types of artificial pins have been developed so far. These two types of artificial pins will be explained in turn.

[0202] The first artificial pin is ReBa ２ Cu ３ O ７－ｘ , especially YBa ２ Cu ３ O ６．９３ These are artificial pins contained in superconducting wires. The composition of this wire is YBa ２ Cu ３ O ６．９３ A superconductor unit cell and a Dy with a size of approximately 50 nmΦ that exists independently of it. ２ O ３ This wire is uniform throughout, and the oxygen count is estimated to be 6.93, therefore, YBa ２ Cu ３ O ６．９３ It is described as a superconductor.

[0203] Dy ２ O ３ YBa ２ Cu ３ O ６．９３ This substance has a very large lattice mismatch of 26%. Therefore, Dy ２ O ３ The perovskite structures of YBCO are not continuous and are formed independently. This superconducting wire was deposited using the TFA-MOD method, and since a liquid phase is formed during growth, if the lattice mismatch is large, they grow independently of each other. Therefore, Dy ２ O ３ and YBa ２ Cu ３ O ６．９３ Therefore, they likely have very few common lattice points.

[0204] This superconductor first exhibits non-superconducting tetragonal YBa at a temperature estimated to be 750-800°C. ２ Cu ３ O ６．００ A unit cell is formed, and independently of it, Dy ２ O ３ Many particles are formed. ２ O３ The particles are thought to function as artificial pins, and their amount is estimated to be around 15%.

[0205] Tetragonal YBa ２ Cu ３ O ６．００ The unit cell undergoes oxygen annealing to produce YBa ２ Cu ３ O ６．９３ It forms a unit cell, achieving the highest performance characteristics as a superconductor. Oxygen annealing changes the crystal structure from tetragonal to orthorhombic, changing the angle between the a-axis and b-axis from 90 degrees to 89 degrees. YBa ２ Cu ３ O ６．９３ The unit cell is Dy ２ O ３ It appears that there is almost no bonding between the particles and the lattice, and YBa is present throughout the superconductor. ２ Cu ３ O ６．９３ It is presumed that a superconductor is being formed.

[0206] This superconductor is YBa throughout ２ Cu ３ O ６．９３ The basis for claiming it is a superconductor is as follows: Purchase this wire and make precision T ｃ Measurements were taken, and 10 samples were measured with a distance of 3 cm between terminals, but all were T ｃ The value was 90.7 ± 0.1 K. This result is T ｃ At the measurement point where continuity is present, T is measured at all passing points. ｃ This indicates that the value was 90.7K.

[0207] Another reason why the inside of this superconducting wire is homogeneous is that no noise is produced when a large current is passed through it all at once. If the majority of this wire does not exhibit the highest performance, but only a portion does, then T ｃ The value was 90.7K, which resulted in the T of a 3cm long sample. ｃ Let's assume the current was measured at 90.7K. If the current applied to that wire is increased from 0A to 100A in 5 seconds, the current will reroute. If a magnetic field of 15T is applied in this state, noise should be generated by the rerouted current. However, no such noise is detected at the 0.1μV level.

[0208] In this wire, YBa ２ Cu ３ O ６．９３ Unit cell and Dy ２ O ３ I don't think the number of connection points with particles is completely zero. However, I believe their number is extremely small. I will explain the reason for this next.

[0209] YBa prepared using the TFA-MOD method ２ Cu ３ O ６．９３ Planview TEM observations have revealed that it has unit cell aggregates (blocks) of approximately 50 × 200 nm. Since the length of a unit cell is 0.39 nm, this results in an aggregate of 130 × 530 unit cells.

[0210] The inventor himself has never performed Planview TEM or cross-sectional TEM observation of this wire. However, judging from the published papers, Dy ２ O ３ The particles are formed in independent 50 nm x 50 nm regions, and YBa ２ Cu ３ O ６．９３ Even if there were contact points with the unit cell, it is easy to imagine that the number of grid cells would be less than 1 / 10,000. If we assume a grid of 1 / 10,000, Dy ２ O ３ Particles are bonded together in a lattice and either oxygen is absorbed or donated, resulting in YBa ２ Cu ３ O ６．９３ Even if the number of oxygen atoms in a unit cell is slightly different, the overall effect is virtually zero. This is likely why a uniform superconductor is formed.

[0211] From the above, it can be inferred that this superconducting wire material possesses high uniformity.

[0212] This superconducting wire is 50 nm in size Dy ２ O ３ A key feature is the presence of particles. As explained in the discussion of artificial pins, this artificial pin will not work at 30K. It is an artificial pin specifically for 77K. However, this wire is YBa ２ Cu ３ O６．９３ As discussed, the unit cell has a 100% superconducting potential. And Dy ２ O ３ The particle has a superconducting potential of 0%.

[0213] As mentioned earlier, the quantum magnetic flux at 77K is 50 nmΦ. It was explained that the 50 nm-sized artificial pin reduces its influence. This artificial pin allows the superconducting potential of the superconducting wire to be 0% and 100%. Therefore, this superconducting wire is considered to have the optimal configuration at 77K. When used at 77K, YBa ２ Cu ３ O ６．９３ Theoretically, it can be seen that no higher superconducting wires exist using superconductors.

[0214] Another type of superconducting wire that has been developed is the Artificial Pinning Center, proposed by Professor M. Driscoll. This research is still being pursued by many researchers worldwide. However, it lacks stability and cannot be applied to large-scale equipment for extended periods, or it quenches even when applied. This explanation will focus on the artificial pinning center.

[0215] This superconducting wire has a 26% lattice mismatch. ２ O ３ Because particles were used, the size became 50 nmΦ, which meant it couldn't be used at 30 K. ２ O ３ The particles are ReBa ２ Cu ３ O ７－ｘ This was because the unit cells grew independently. Therefore, the motivation for developing the Artificial Pinning Center was likely the idea that artificial pins, with smaller lattice mismatches and growing while being partially influenced, could be made smaller.

[0216] Furthermore, here ReBa ２ Cu ３ O ６．９３ Instead of writing ReBa ２ Cu ３ O７－ｘ The reason for this is that the oxygen count deviates from the average value of 6.93. The explanation for this will be given later.

[0217] The most widely developed artificial pin used as an artificial pinning center worldwide is BaZrO ３ It seems so. YBa ２ Cu ３ O ７－ｘ The lattice mismatch with superconductors is said to be about 9%, and by partially forming lattice bonds during growth, BaZrO ３ It is believed that this prevented excessive growth, resulting in the creation of artificial pins with a diameter of 5 nm.

[0218] 5 nmΦ size BaZrO ３ Cross-sectional images of the artificial pins have also been published, demonstrating a significant improvement in magnetic field characteristics, suggesting that the presence of 5 nmΦ artificial pins would have improved these properties. These results are highly reliable and supported by scientific evidence.

[0219] However, on the other hand, as other announcements show, BaZrO ３ ReBa with artificial pins ２ Cu ３ O ７－ｘ It is also true that superconductors have an internal heterogeneity. While clues to why this internal heterogeneity occurs are readily available, no one has attempted to improve or modify them. This situation is incomprehensible to the inventor. It's unclear whether others simply don't understand it, or if they understand it but find it too difficult to tackle, leaving it untouched.

[0220] Before explaining the cause of this non-uniformity, let's explain that another type of artificial pin used as an artificial pinning center also exhibits similar behavior. This material is, for example, BaHfO ３ Artificial pins and BasnO ３ These are artificial pins. These artificial pins are made of BaZrO ３ Similar to artificial pins, they have relatively small lattice mismatches, and the ability to partially form lattice bonds during growth allows artificial pins to be made smaller.

[0221] These artificial pins have adjacent ReBa ２ Cu ３ O ７－ｘ There have been numerous reports that oxygen is being removed from superconductors. A typical example is BaZrO2. ３ Let's take artificial pins as an example. ReBa ２ Cu ３ O ７－ｘ Unit cell and BaZrO ３ These two materials form a lattice bond. Although both have a perovskite structure, they are fundamentally dissimilar substances, so it is natural that oxygen annealing will result in either an excess or deficiency of oxygen in one of them.

[0222] When fabricating these superconductors, the main deposition methods are Pulsed Laser Deposition and Metal Organic Chemical Vapor Deposition. These deposition methods also involve first depositing a non-superconductor tetragonal ReBa at a temperature of 700°C to 800°C. ２ Cu ３ O ６ To make BaZrO ３ It has a volume ratio of 15%, and the artificial pins are made small, so lattice bonding is possible in many places. ２ Cu ３ O ６ This is how it will be made.

[0223] ReBa ２ Cu ３ O ６ and BaZrO ３ The oxygen annealing will be performed on a mixture of these substances. ReBa ２ Cu ３ O ６ The volume ratio is 85%, and BaZrO ３ The volume ratio is 15%. ReBa ２ Cu ３ O ６ However, ReBa exhibits the greatest superconductivity. ２ Cu ３ O ６．９３ Oxygen annealing is performed in such a way that it results in the desired outcome.

[0224] Here, BaZrO ３ReBa ２ Cu ３ O ６ Reports have shown that it is easier to inhale oxygen than [another method]. Therefore, oxygen annealing allows ReBa ２ Cu ３ O ６．９３ In some places, ReBa ２ Cu ３ O ６．８ Ya ReBa ２ Cu ３ O ６．７ There are some cases where this is the case. As mentioned earlier, here, ReBa ２ Cu ３ O ６、 ReBa ２ Cu ３ O ６．８ ReBa ２ Cu ３ O ６．７ We will discuss the superconductivity characteristics of each material assuming values ​​of 100%, 30%, and 10%.

[0225] For example, BaZrO ３ What happens if it is an oxygen-donating substance? ReBa ２ Cu ３ O ６．９３ Some places make it, while others use ReBa ２ Cu ３ O ７．００ Ya ReBa ２ Cu ３ O ７．１０ It is thought that such areas will also be created. In this case, the superconducting characteristics will be 100%, 0%, 0%. In such superconductors, there will be many places where the superconducting current path is interrupted, and extremely J ｃ The value is expected to decrease. Therefore, it appears that research on artificial pins made of that type of oxygen-donating material has been suspended at the preliminary investigation stage.

[0226] BaZrO, which has been studied for a long time at the Artificial Pinning Center ３ BaHfO ３ ,BaSnO ３All of these materials appear to be oxygen-inhibiting materials. This likely explains the non-uniform superconductivity, with superconductivity levels ranging from 100% to 30% and 10%. Supporting experimental results have also been obtained.

[0227] When this superconducting wire is measured, T ｃ The value is GdBa ２ Cu ３ O ６．９３ The temperature was 85-90K, which is lower than the optimal 92.5K. This indicates that the 3cm measurement terminals were not connected in the 92.5K range. A total of 5 samples were measured, but T ｃ The values ​​varied between 85 and 90K.

[0228] We investigated whether voltage noise would be generated in this superconducting wire by rapidly increasing the current value from 0A to 100A in 5 seconds at 15T. A severe noise voltage of 50-100μV was observed. This suggests that the internal characteristics are non-uniform, causing the current to bypass various points, and generating voltage noise under the applied magnetic field conditions.

[0229] These results also reveal another important fact: the current values ​​were examined in the cross-sectional direction of the superconductor, and from left to right, J ｃ Suppose the values ​​were 100%, 30%, and 10%. If the values ​​are 100%, 30%, and 10% in the next region, there is no problem. However, in the next region, J ｃ If the values ​​are 10%, 30%, and 100%, the current will be rerouted, and in some cases, the 10% portion will likely burn out in the nanoscale.

[0230] This phenomenon occurs even at current values ​​below the overall rated current of the superconducting wire, and it is thought that burnout can occur in the nanoscale even at 50% of the rated current. With use, the maximum rated current gradually decreases, and eventually, quenching may occur even at 50% of the rated current.

[0231] The possibility of combustion in the nanoscale leading to a decrease in properties has not been actually confirmed. However, based on numerous related data, it is a phenomenon that is quite possible. If combustion occurs in the nanoscale, that part will no longer be a superconductor. We will refer to this phenomenon as nanoburn.

[0232] Research presentations on nanoburn and how to address internal heterogeneity, as mentioned above, were completely absent from EUCAS 2023, the largest superconductivity conference held recently. It seems that either this phenomenon is not recognized at all, or even if recognized, it is being tolerated because it is difficult to address. However, it seems difficult to build and stably operate large-scale equipment using superconducting wires that exhibit such phenomena, and this is indeed the case.

[0233] A 500m-long wire produced using the PLD method was reported as early as 2007. It is now 2024. In the past 17 years, there has been no record of successfully passing high currents repeatedly through large-scale equipment. The complete lack of reported cases suggests that some fundamental problem has not been addressed. If research into this issue is initiated and progress is made, superconducting wires produced by Artificial Pinning Center may become practical.

[0234] As described above, the superconductor by the Artificial Pinning Center has an internal J ｃ The values ​​are non-uniform, T ｃ The values ​​are unstable. Therefore, the internal superconducting potential is not necessarily adjacent to 100%; there may be places where 30% or 10% is adjacent to 100%. If there is a 10% adjacent to 0%, the pinning force will be only 1 / 10 of what it would be if there was a 100% adjacent to 0%. In other words, there will be countless regions inside with relatively weak pinning force. Furthermore, if it is non-uniform in three dimensions, the quantum magnetic flux will deviate through various routes, and the properties will deteriorate because it cannot be pinned.

[0235] This internal inhomogeneity is likely to exacerbate the problem at temperatures of 20K and 30K, where the quantum magnetic flux decreases to 3.5 nmΦ and 5.0 nmΦ, respectively. At low temperatures, the quantum magnetic flux decreases, so we would like the superconducting potential of the adjacent region to change significantly. However, if there is an oxygen-attracting artificial pin, the surrounding superconducting potential decreases, and the pinning force decreases. The above considerations indicate that, in principle, artificial pins are created that either do not exert a pinning force or have a reduced pinning force.

[0236] This artificial pinning technology, commonly known as an Artificial Pinning Center, will be referred to here as PLMP (Plant-Like Pinning Matrix) because it creates partial lattice bonding due to close lattice mismatches. This is by no means an attempt to negate the Artificial Pinning Center. PLMPs include oxygen-absorbing and oxygen-donating types, and both are included in the classification of PLMP. It should also be added that the term Artificial Pinning Center seems to refer only to the oxygen-absorbing type.

[0237] Based on previous explanations of NLMP and PLMP, neither can stably form artificial pins of approximately 5 nm in diameter, nor can they produce superconductors with a uniform oxygen count of 6.93 inside the superconductor. As a solution, the inventors' group proposed and has been developing CARP, a clustered atom substitution type artificial pin.

[0238] CARP localizes the superconducting unit cell by placing PrBCO inside it, and Pr ３＋ →Pr ４＋ This is an artificial pin that utilizes this property. Results from bulk superconductors suggest that the c-axis length of Pr is shortened by 14% due to the increase in oxygen within the perovskite structure caused by the valence change. This method involves the formation of an aggregate of non-superconductors, where the elements adjacent to the Pr site are also affected by the valence change of Pr.

[0239] In this specification, artificial pins that do not grid-match are classified as NLMPs, and artificial pins that partially grid-match are classified as PLMPs. CARPs are virtually grid-matched artificial pins and can be called SLMPs. CARPs have very little grid mismatch between their constituent unit cells.

[0240] The unit cells used by CARP, when discussed at the moment the grid is assembled, have a matrix of YBa ２ Cu ３ O ６ In this case, and if lanthanum (La) is not used as the rare earth element (Re), then PrBa ２ Cu ３ O ６ This is the maximum size, and the minimum size is LuBa ２Cu ３ O ６ These are all tetragonal non-superconductors.

[0241] YBa ２ Cu ３ O ６ PrBa against ２ Cu ３ O ６ Regarding the lattice mismatch, based on knowledge from bulk superconductors, the latter is estimated to be +1.11%. It has long been known that lanthanide elements exhibit lanthanide contraction, meaning that as the atomic number increases, the ionic radius of the +3 valent element decreases, and the lattice constant also decreases.

[0242] Meanwhile, YBa ２ Cu ３ O ６ LuBa ２ Cu ３ O ６ Since there is no data in related papers regarding the lattice mismatch, the one atomic number earlier, YbBa, is used. ２ Cu ３ O ６ If we substitute with this, it is +0.47%. Furthermore, if we use TmBa with the atomic number one step earlier... ２ Cu ３ O ６ Since it is +0.31%, the smallest LuBa ２ Cu ３ O ６ However, it seems to be around +0.60%. These ReBa ２ Cu ３ O ６ Then, oxygen annealing is performed on ReBa ２ Cu ３ O ６．９３ However, this is because oxygen annealing does not change the valence of the rare earth element (Re) or the structure. Therefore, the lattice mismatch after oxygen annealing is also considered to be almost the same.

[0243] The only significant change in lattice length is observed in bulk material studies of PrBa. ２ Cu ３ O ６．９３It is said that Pr changes from a +3 valency to a +4 valency due to oxygen annealing, and oxygen enters the lattice to compensate for that valency. Originally, PrBa ２ Cu ３ O ９ ABO, which should be ３ The type perovskite structure is PrBa ２ Cu ３ O ６ In that case, the number of oxygen atoms is significantly reduced from nine, and there is a lack of oxygen between the Cu atoms at site B.

[0244] When the valence of Pr becomes +4, the probability of oxygen being present at the Cu sites increases in order to maintain electrical neutrality. As a result, studies on bulk superconductors have shown that the c-axis length shrinks by approximately 14%. CARP, an artificial pin, is a technology consisting of clustering and Pr pins, and Pr pins are formed in this way. Therefore, in a perovskite structure that has been formed as a tetragonal crystal, if the amount of Pr is small, the perovskite structure is maintained while physical contraction causes PrBa ２ Cu ３ O ７－ｘ The unit cells become non-superconducting, and the four adjacent unit cells inside the a / b axis also become non-superconducting.

[0245] Furthermore, in the c-axis direction of the contracted Pr, the Ba, Ba, and Re are aligned, so the upper and lower unit cells do not become non-superconducting. Therefore, it is thought that a 5-fold degradation phenomenon occurs. Thus, CARP is a technology that uses unit cells with a lattice mismatch of virtually a maximum of +1.11%, and can be said to be a technology with virtually zero or near-zero lattice mismatch. For this reason, CARP will be classified as SLMP here.

[0246] PLMP has a lattice mismatch of approximately 9%, and various cross-sectional TEM observations have reported strain structures resulting from this. On the other hand, CARP does not have such strain structures at all. It forms a continuous perovskite structure, and then the pr changes valence to form a non-superconducting unit cell. This is not the only major structural difference between PLMP and SLMP.

[0247] As explained above, CARP is known to exhibit a five-fold degradation phenomenon. Therefore, PrBa ２ Cu ３ O ７－ｘ In structures where Pr is uniformly dispersed within a superconductor, it has been confirmed that the superconducting properties can decrease by 50% when, for example, 10% Pr is present. ２ Cu ３ O ７－ｘ If only that exists, a five-fold degradation phenomenon occurs, resulting in a total of 50% of the unit cells becoming non-superconducting.

[0248] In addition to the above, to confirm the internal uniformity, we conducted a test on the superconducting film containing CARP by applying current values ​​from 0A to 100A for a short period of 5 seconds under a 15T magnetic field, similar to the experiments conducted with NLMP and PLMP, to see if any noise of 1μV was generated. The results showed that the noise was almost zero, with noise only detected at the 0.1μV level. This suggests that the internal structure of the superconducting film containing CARP is also uniform, and that it has a high potential for stable long-term use in large-scale equipment.

[0249] Tests to determine the future properties of CARP have already been conducted, using 10% PrBa ３ Cu ３ O ７－ｘ YBa is uniformly dispersed ３ Cu ３ O ７－ｘ In superconductors, it is known that the superconducting properties have decreased by 50%, and T ｃ The value has been consistently measured at 90.7K. This value is YBa ３ Cu ３ O ７－ｘ This result indicates that the oxygen count in the superconductor was maintained at 6.93.

[0250] As explained above, YBa ３ Cu ３ O ７－ｘ The highest performance of a superconductor is achieved when it is a thin-film superconductor. ｃThis is the case when the value is 90.7K. In that case, the number of oxygen atoms is 6.93. And naturally, 50% of the unit cells formed by CARP are non-superconducting, and YBa ３ Cu ３ O ７－ｘ A superconductor consists of many adjacent unit cells. The superconducting potentials of these two adjacent cells are 0% and 100%.

[0251] PrBa ３ Cu ３ O ７－ｘ This is a single unit cell with a size of 0.39 nm in the a / b axis direction. However, with CARP, the size can be adjusted to around 5 nm x 5 nm depending on the combination and manufacturing conditions. The CARP produced in this way has an internal superconducting potential of 0% and a superconducting potential of 100% in the superconducting region. In other words, experimental results show that the best structure can be created with artificial pins of 5 nm x 5 nm size.

[0252] CARP is a structure that, according to the inventor's assumptions, only appears when the pseudo-liquid-phase network model of the TFA-MOD method is activated. Spain's group is attempting to deposit films at high speed. However, in the TFA-MOD method, if unit cells that are not oriented in the c-axis direction appear, it is necessary to correct them. This results in a structure where almost all cells are aligned in the c-axis direction.

[0253] In the ultrafast growth of the Spain group, the growth rate is accelerated to a level where unit cell repair fails, thus creating a stable structure for YBa ３ Cu ３ O ７－ｘ It seems that this has not been done.

[0254] Incidentally, there are other SLMPs besides CARP. These are techniques that deliberately cause oxygen annealing to fail, for example, SmBa ２ Cu ３ O ７－ｘ SmBa ２ Cu ３ O ７－ｘIt is said that substitution between Sm and Ba occurs, resulting in non-superconductivity. Although this does not involve clustering, it is still considered an SLMP and an atomic substitution type artificial pin.

[0255] However, it is unknown how the surrounding unit cells will behave in a superconductor where Ba substitution has occurred. ｃ It is also unknown whether the value is maintained. Ba substitution is assumed to occur randomly, and SmBa ２ Cu ３ O ７－ｘ Within the structure, there is a 2 / 3 probability that Ba is in the center, and a 1 / 3 probability that Sm is in the center, suggesting a random structure. Therefore, adjacent elements like T in CARP are also present. ｃ Measurements and other such procedures are expected to be extremely difficult. The superconducting potential of adjacent unit cells is not necessarily 100% and 0%.

[0256] The above provides a scientific explanation regarding artificial pins, and NLMP is best at 77K YBa ２ Cu ３ O ６．９３ Regarding the ability to create superconductors, PLMP explained that the distribution of oxygen atoms due to oxygen annealing poses a problem that needs to be solved. It also explained that SLMP, to which CARP belongs, is currently the closest technology to being able to create artificial pins used in 30K and 20K applications.

[0257] CARP was expected to be able to form stable artificial pins with a diameter of 5 nm, but the inventors have newly discovered that amorphous regions are formed on the upper part of the film, which negates the effect of the artificial pins. The structure of the amorphous regions was such that they were located along the grain boundaries on the upper part of the film.

[0258] The TFA-MOD method is known to form aggregates of unit cells approximately 50 nm × 200 nm in size, based on its growth mechanism. These unit cell aggregates correspond to the blocks shown in Figures 2(a) and 2(b). Furthermore, Planview TEM observations of samples in which CARP formation was attempted revealed that amorphous regions exist along the grain boundaries of these unit cell aggregates.

[0259] Figures 13(a) and 13(b) are enlarged views including a portion of the oxide superconducting layer of the comparative example. Figure 13(a) is a top view, and Figure 13(b) is a cross-sectional view. Figures 13(a) and 13(b) correspond to Figures 2(a) and 2(b) of the first embodiment.

[0260] The comparative oxide superconductor includes an oxide superconducting layer 31. The comparative oxide superconducting layer 31 includes a main region 30a and a sub-region 30b, similar to the oxide superconducting layer 30 of the first embodiment.

[0261] The main region 30a has superconducting properties. The sub-region 30b does not have superconducting properties.

[0262] The comparative example oxide superconducting layer 31 differs from the oxide superconducting layer 30 of the first embodiment in that the volume ratio of the sub-region 30b to the oxide superconducting layer 31 is greater than 1.10%.

[0263] Figures 14(a) and 14(b) are transmission electron microscope (TEM) images of the oxide superconducting layer of the comparative example. Figures 14(a) and 14(b) are TEM images of the second surface F2 of the oxide superconducting layer 30. Figure 14(b) is an enlarged view of the area enclosed by the frame in Figure 14(a).

[0264] Figures 14(a) and 14(b) show YBa ２ Cu ３ O ７－ｘ This is a Planview TEM image.

[0265] In Figures 14(a) and 14(b), the main region 30a and the sub-region 30b are observed. The sub-region 30b is located between two adjacent main regions 30a.

[0266] Figures 14(a) and 14(b) correspond to Figures 4(a) and 4(b) of the first embodiment. The width of the sub-region 30b in the comparative example is greater than the width of the sub-region 30b in the first embodiment.

[0267] The comparative example oxide superconducting layer 31 differs from the oxide superconducting layer 30 of the first embodiment in that it is manufactured using barium acetate, which does not contain crystalline water, as a raw material.

[0268] In the TFA-MOD method, superconducting film deposition begins with solution synthesis. Solution synthesis is performed according to the flowchart shown in Figure 5. Each acetate salt to be used in the final ratio is dissolved in pure water in that ratio and reacted with an equimolar amount of trifluoroacetic acid to form trifluoroacetate. The resulting trifluoroacetate is purified twice by the SIG method to obtain a coating solution.

[0269] A superconductor is obtained from the resulting coating solution according to the flowchart shown in Figure 6. First, a gel film is obtained by methods such as dip coating or spin coating. At this point, most of the solvent evaporates, so a gel film consisting mainly of trifluoroacetate is obtained.

[0270] The gel film decomposes organic matter in the firing profile shown in Figure 7, yielding oxidized fluorides. The gel film absorbs water vapor and shrinks, but above 100°C, the shrinkage due to absorption ceases. At that temperature, there is a possibility that copper trifluoroacetate, which has the smallest molecular weight, may sublimate, so humidification is performed from 100°C. It is said that humidification causes partial hydrolysis of copper trifluoroacetate, forming oligomers and preventing sublimation.

[0271] The decomposition of organic matter is carried out at X in Figure 7. The decomposition temperature of trifluoroacetate is also a function of the heating rate, but in the calcination profile where the temperature rises from 200°C to 250°C in about 10 hours, the decomposition reaction is thought to occur around 210°C to 240°C. After that, the decomposition residue is removed in steps Y and Z to obtain a calcined film.

[0272] The calcined film consists of oxides and fluorides of six different metal elements. Of these six elements, only Cu primarily forms CuO, although some fluoride is also present. The other five elements form unbalanced compounds of fluoride and oxide. Fluorine is partially substituted into the oxides, resulting in these unbalanced compounds. This unbalanced structure maintains an amorphous state without forming crystals.

[0273] The resulting calcined film becomes a superconductor through the final calcination profile shown in Figure 8 and oxygen annealing. Humidification is carried out from 100°C, and a characteristic of the TFA-MOD method is that it grows while forming a liquid phase. The maximum temperature is between 725°C and 800°C, at which temperature a perovskite structure is formed. However, the structure is tetragonal and the number of oxygen atoms is 6.00. Note that oxides with this tetragonal structure and 6.00 oxygen atoms are not superconductors.

[0274] In Figure 8, after the final firing is complete, a drying gas replacement is performed, and after the drying gas is circulated, pure oxygen annealing is carried out at a temperature between 375°C and 525°C. This results in an oxygen count of 6.93. As explained earlier, in the TFA-MOD method, the oxygen count of NLMP and SLMP superconductors is 6.93 throughout the entire range.

[0275] On the other hand, using the TFA-MOD method, BaZrO ３ Numerous attempts have been made to create artificial pins using PLMPs. In that case, as explained above, there may be some regions with 6.93 oxygen atoms, but if it is an oxygen-absorbing PLMP, the average value will be even smaller, resulting in a random structure where the number of oxygen atoms varies from place to place.

[0276] Even when a PLMP superconducting film is formed using the TFA-MOD method, the instability of the oxygen number remains unchanged. Therefore, it is believed that there are no PLMP wires that can be reliably mounted on large products. This is not due to a flawed method, but rather to the non-uniformity during oxygen annealing.

[0277] In the first embodiment, a continuous perovskite structure is formed, but there are four types of elements that can occupy the Y site, such as Pr, Sm, Tm, and Y. Each has an optimal oxygen partial pressure, which is 1 ppm, 20 ppm, 3000 ppm, and 1000 ppm when calcined at 800°C. These superconductors can only have a continuous perovskite structure formed by the TFA-MOD method. This discussion is similar to the descriptions in the registered patents No. 7330152 and No. 7330153 filed by the inventor, so a detailed explanation is omitted here.

[0278] For example, in the Pulsed Laser Deposition method, even a doubling or 0.5x reduction in the optimal oxygen partial pressure can prevent the formation of a perovskite structure. The same is true for Metal Organic Chemical Vapor Deposition. However, in the TFA-MOD method, perhaps due to liquid-phase growth, it seems that the formation of a perovskite structure is determined by the average value of the optimal oxygen partial pressure. As a result, superconductors that form a continuous perovskite structure with multiple elements can be obtained.

[0279] Figure 8 shows a typical temperature profile for the 800°C firing, but the heating profile is gradual from 775°C to 800°C to avoid temperature overshoot at tb3. Even with this, an overshoot of 2-3°C may remain at 800°C, but this is not particularly problematic. The oxygen partial pressure at the maximum temperature depends on the matrix phase. In the case of YBCO superconductor firing, it is 1000 ppm at 800°C, and the optimal oxygen partial pressure is halved for every 25°C decrease in temperature. That is, it is 500 ppm at 775°C and 250 ppm at 750°C. In this firing, YBa ２ Cu ３ O ７－ｘ In the case of the system, YBa ２ Cu ３ O ６ A superconductor is formed. At this point, it is not a superconductor.

[0280] In the first embodiment, for example, a charred metal with a maximum temperature of 750°C is used. In this case, the same heating rate as in Figure 8 is used until the temperature is 25°C below the maximum temperature, and then the heating rate is reduced to raise the temperature to the maximum temperature.

[0281] During the final firing at the highest temperature, a drying gas is introduced at tb4 before the firing is complete and the temperature begins to decrease. This is because the humidifying gas decomposes the superconductor into oxides below 700°C. Oxygen annealing is performed at tb6 to reduce the number of oxygen atoms in the perovskite oxide from 6.00 to 6.93. At this oxygen number, it becomes a superconductor. However, PrBa ２ Cu ３ O ７－ｘ Only PrBa has a perovskite structure but is not a superconductor. ２ Cu ３ O７－ｘ Since it also forms a perovskite structure, it is thought to be trivalent when formed from a pseudo-liquid phase during calcination. The rare earth element Ce, which takes a tetravalent form, is CeO ２ It may also exist without forming a perovskite structure. ３＋ This is evidence of that fact. Subsequently, it is currently unknown whether the temperature at which it becomes tetravalent is above or below the oxygen annealing temperature. The oxygen annealing temperature is, for example, between 375°C and 525°C. After the temperature holding period ends, furnace cooling is performed from tb8.

[0282] Next, we will explain how to obtain a structure in which the effects of CARP can be exerted in the first embodiment. As shown in Figure 5, the TFA-MOD method is a method that uses metal acetate as a raw material. Here, we will explain CARP in which Y is substituted with 2% Pr, 2% Sm, and 4% Tm.

[0283] As described in the registered patent, CARP is a method for accumulating large and small unit cells by utilizing the slight difference in lattice constants that occurs when forming a perovskite structure. This unit cell accumulation is thought to be achievable by mixing elements within a predetermined range.

[0284] As shown in Figures 13(a), 13(b), 14(a), and 14(b), the comparative oxide superconducting layer 31 includes a sub-region 30b. The width of the sub-region 30b in the comparative example is greater than the width of the sub-region 30b in the first embodiment. The depth of the sub-region 30b in the comparative example is greater than the depth of the sub-region 30b in the first embodiment. The sub-region 30b is, for example, an amorphous region.

[0285] The volume percentage of the subregion 30b in the comparative example is greater than 1.10%.

[0286] If the volume ratio of the amorphous sub-region 30b in the oxide superconducting layer 31 is large, it is thought that the CARP contained in the main region 30a of the oxide superconducting layer 31 cannot exert its effect. This will be explained below.

[0287] The amorphous region is thought to function as a quantum flux gallery (QFG) where multiple quantum magnetic fluxes gather and move.

[0288] In the comparative example of the oxide superconducting layer 31, the size of the amorphous region is large, and the volume ratio of the amorphous region in the oxide superconducting layer 30 is also large. Therefore, quantum magnetic flux is more likely to enter the amorphous region, which has a smaller superconducting potential than CARP. When quantum magnetic flux enters the amorphous region, it moves in the direction of the applied stress, and another quantum magnetic flux enters the amorphous region and moves along the same path. As a result, the quantum magnetic flux exceeds the pinning force at the edges and enters the superconducting layer. For this reason, even if CARP is formed, for example, it is thought that the superconducting properties in a magnetic field of 20-30K will not be significantly improved.

[0289] In the oxide superconducting layer 30 of the first embodiment, the size of the amorphous region is smaller compared to the oxide superconducting layer 31 of the comparative example, and the volume ratio of the amorphous region in the oxide superconducting layer 30 is also smaller. Therefore, quantum magnetic flux can more easily enter the CARP, which has a lower superconducting potential than the amorphous region. As a result, the CARP is thought to function effectively, and the superconducting properties in a magnetic field at 20-30K are expected to be greatly improved.

[0290] In the first embodiment, the volume ratio occupied by the sub-region 30b in the oxide superconducting layer 30 is 0.001% or more and 1.10% or less. From the viewpoint of improving the superconducting properties of the oxide superconductor 100, the volume ratio occupied by the sub-region 30b in the oxide superconducting layer 30 is preferably 1.0% or less, more preferably 0.5% or less, and even more preferably 0.3% or less.

[0291] The area ratio of the second surface F2 of the sub-region 30b in the oxide superconducting layer 30 is preferably 10% or less, preferably 5% or less, and more preferably 3% or less.

[0292] From the viewpoint of improving the superconducting properties of the oxide superconductor 100, the width of the second surface F2 of the sub-region 30b in the direction perpendicular to the elongation direction is preferably 10 nm or less, and more preferably 5 nm or less.

[0293] From the viewpoint of improving the superconducting properties of the oxide superconductor 100, the depth of the sub-region 30b in the direction from the second surface F2 to the first surface F1 is preferably 10% or less, and more preferably 5% or less, of the thickness of the oxide superconducting layer 30 in the direction from the second surface F2 to the first surface F1.

[0294] Furthermore, it is difficult to completely eliminate the sub-region 30b within the oxide superconducting layer 30. Even if all crystalline raw materials are used, some decomposition products will still be present, so it is estimated that the maximum purity achievable is only 99.9999%. In that case, the volume percentage occupied by the sub-region 30b will be 0.001%.

[0295] The sub-region 30b has the function of improving the reliability of the metal layer 40 formed on the oxide superconducting layer 30. For example, suppose a silver film with a thickness of approximately 1 μm is deposited on the oxide superconducting layer 30 as the metal layer 40. In this case, because the bond between the amorphous sub-region 30b and the silver film is weak, it plays a role in preventing the silver from cracking due to the temperature difference between the silver film during deposition and at room temperature. By suppressing cracking, the reliability of the metal layer 40 is improved.

[0296] From the viewpoint of improving the reliability of the metal layer 40, the volume ratio occupied by the sub-region 30b is preferably 0.05% or more, and more preferably 0.01% or more.

[0297] In the oxide superconductor 100 of the first embodiment, the critical current densities obtained when magnetic fields of 0.5T, 2.0T, 3.0T, and 5.0T are applied to the oxide superconducting layer 30 in the direction from the first surface F1 to the second surface F2 at a temperature of 77K are α (MA / cm²), respectively. ２ ), β(MA / cm ２ ), γ (MA / cm ２ ), and δ(MA / cm ２ ) is defined as follows. In this case, it is preferable that at least one of the following inequalities holds: α / β > 4.0, α / γ > 10, or α / δ > 70.

[0298] From the viewpoint of improving the superconducting properties of the oxide superconductor 100, it is more preferable that all of the following inequalities hold: α / β > 4.0, α / γ > 10, and α / δ > 70.

[0299] From the viewpoint of improving the superconducting properties of the oxide superconductor 100, it is even more preferable that at least one of the following inequalities holds: α / β > 6.0, α / γ > 20, or α / δ > 200.

[0300] From the viewpoint of improving the superconducting properties of the oxide superconductor 100, it is even more preferable that all of the following inequalities hold: α / β > 6.0, α / γ > 20, and α / δ > 200.

[0301] From the viewpoint of improving the superconducting properties of the oxide superconductor 100, it is even more preferable that at least one of the following inequalities holds: α / β > 10, α / γ > 40, or α / δ > 1000.

[0302] From the viewpoint of improving the superconducting properties of the oxide superconductor 100, it is even more preferable that all of the following inequalities hold: α / β > 10, α / γ > 40, and α / δ > 1000.

[0303] In both the oxide superconducting layer 30 of the first embodiment and the oxide superconducting layer 31 of the comparative example, amorphous regions are formed along low-angle grain boundaries. The amorphous regions are sub-regions 30b. Due to the manufacturing process of the TFA-MOD method, impurities and decomposition products exist within the pseudo-liquid phase, and since these cannot participate in the growth of unit cells, they are pushed out to the upper grain boundaries.

[0304] It was found that amorphous regions are concentrated at low-angle grain boundaries when forming an oxide superconducting layer using the TFA-MOD method. Furthermore, it is thought that if the amount of amorphous regions is greater than the amount of CARP formed inside the oxide superconducting layer, the CARP will not be able to exert its effect.

[0305] Numerous experiments have been conducted focusing on CARP, in which 8% of the yttrium sites in the oxide superconducting layer are replaced. In this case, if 10% of the amorphous region is present, the quantum magnetic flux will concentrate in that amorphous region. This concentrated region is called the quantum magnetic flux gallery. Unless the amorphous region is reduced, good CARP properties cannot be obtained.

[0306] So, how much impurity has an effect? ​​If it exceeds 1% of the total volume, it will have an effect. Let's assume that an amorphous region is formed in the oxide superconducting layer with a width and thickness ratio of 10% each. In this case, the volume ratio of the amorphous region is 1%. In this case, CARP tries to fix the quantum magnetic flux with an 8% reduction in superconducting potential, while QFG tries to pin the quantum magnetic flux with a 10% reduction in superconducting potential.

[0307] Since quantum magnetic flux simply concentrates where the superconducting potential is small, if it concentrates at the QFG, the quantum magnetic flux will move in the direction of the stress, overcome the pinning force at the tip, and enter the superconducting region. In this way, the superconducting properties deteriorate.

[0308] Even if quantum magnetic flux accumulates in the QFG, this does not mean that CARP does not improve the properties at all. Even if most of the quantum magnetic flux enters the QFG, it is thought that some will remain in the CARP. Furthermore, if there are two CARPs in the thickness direction and quantum magnetic flux is trapped there, the decrease in superconducting potential will be 16%, and it is thought that some quantum magnetic flux will be pinned to the two CARPs without entering the QFG. This is thought to be why the performance improvement effect observed in oxide superconductors using CARP in the past was only 30% compared to YBCO.

[0309] However, in order to utilize CARP's inherent pinning power and improve its magnetic field characteristics, it is necessary to suppress the formation of this QFG (Quick Field Generator). Only by suppressing QFG formation can CARP exhibit its optimal performance.

[0310] The question then becomes, how much QFG formation inhibition is necessary? This seems to depend on the amount of decomposition of the raw acetate. The purity of the raw acetate can be determined by precise thermal analysis using thermogravimetry. This is because decomposition reduces the weight loss. However, the measurement accuracy is only 0.2%.

[0311] What became clear was that if the raw materials were not crystalline, there would be many decomposition products. Therefore, when manufacturing the oxide superconducting layer, Pr, Sm, Tm, Y, and Cu salts were all made from crystalline raw materials. It was found that the amount of impurities of Pr and Sm, which are easily decomposed by light rare earth elements, could be limited to 0.6% even when crystalline raw materials were produced, and the others could be reduced to 0.2%. Even if some QFG remains, a slight improvement in CARP properties can be seen. This is because a pinning force is at work to some extent.

[0312] However, the biggest problem wasn't that, but rather the lack of crystalline barium acetate (BA) salt. Crystalline barium acetate is not available commercially. Some vendors sell it in powder form, while others sell it in pellet form. The pellet form was the only one that offered even a slight improvement in its properties as a CARP (Carbonated Refining Agent).

[0313] Both the powdered and pelletized raw materials are opaque white in color. Since they do not contain water of crystallization, a large amount of the raw material is dissolved in water, and BaCO3 is produced. ３ The only way to analyze it is to collect it by filtration, but the analysis results showed that even the best raw material was 3.0% degraded. The powdered material was degraded by nearly 4.5-6.5% and became BaCO3. ３ There were elements that formed it.

[0314] Assuming all of the above raw materials are in optimal condition, and only the Ba salt has a 3.0% degradation, the amount of impurities can be calculated as 1.12%. This amount exceeds 1.00%, which is enough to form an amorphous region with a width of 10% and a thickness of 10% on top of the superconducting layer as described above. It is thought that improvement of the Ba salt was necessary to achieve the effect of CARP.

[0315] This time, we discussed this with the vendor and decided to try producing a prototype of barium acetate monohydrate, which is not commercially available. Surprisingly, this raw material was colorless and transparent. Until now, we had only seen opaque white raw materials, but this is probably BaCO3 ３ The white color was a result of the formation process, and it is believed that the raw material was originally colorless and transparent.

[0316] By obtaining raw materials containing crystal water, it became possible to measure the amount of impurities using TG thermal analysis. As a result, it was found that even the Ba salt, in monohydrate form, contains only 0.2% impurities. When a solution was synthesized using this and the minimum impurity amounts of all acetate salts, it was found that the amount of impurities in the solution was 0.2%.

[0317] This suppresses the formation of amorphous regions near the surface, as shown in Figures 14(a) and 14(b), allowing the CARP formed internally to exert its intended magnetic field characteristic improvement effect. In other words, if an oxide superconducting layer 30 in which the volume ratio of the sub-region 30b is 1.10% or less can be realized, it is considered possible to realize an oxide superconductor 100 in which the CARP can exert its intended magnetic field characteristic improvement effect.

[0318] A key point of the first embodiment is the deliberate creation of barium acetate monohydrate, which is not commercially available, and the synthesis of a solution with fewer impurities by using barium acetate monohydrate. Figure 14(b) is a high-magnification image of Figure 14(a), and it can be seen that there are many bright white lines clearly visible at each grain boundary. The appearance of these white lines differs depending on the angle, but the X-ray results show that a relatively thick amorphous layer is present.

[0319] As a result, the amount of impurities in the solution is theoretically reduced from 1.14% to 0.20%, a reduction to 1 / 5, and the amount of QFG formation is theoretically suppressed to 1 / 5. The volume ratio of QFG in the oxide superconducting layer can be determined by Planview TEM observation or cross-sectional TEM observation. However, measuring the depth of QFG by Planview TEM observation or cross-sectional TEM for each sample preparation is time-consuming and laborious. Therefore, a simpler method for investigating the structure in which QFG is suppressed will be disclosed in the examples below.

[0320] As described above, according to the first embodiment, an oxide superconductor with improved properties in a magnetic field and a method for manufacturing the same can be provided.

[0321] (Second Embodiment) The oxide superconductor of the second embodiment includes an oxide superconducting layer having a first surface and a second surface facing the first surface, and comprising a first region and a second region. The first region has a continuous perovskite structure and comprises rare earth elements, barium (Ba), and copper (Cu). The rare earth elements include a first element which is praseodymium (Pr), at least one second element selected from the group consisting of yttrium (Y), europium (Eu), gadolinium (Gd), dysprosium (Dy), holmium (Ho), and erbium (Er), and at least one third element selected from the group consisting of yttrium (Y), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu). The first, second, and third elements are all distinct elements. If the second and third elements are not yttrium (Y), the atomic number of the second element is less than the atomic number of the third element. If the second element is yttrium (Y), the third element is at least one element selected from the group consisting of erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu). If the third element is yttrium (Y), the second element is at least one element selected from the group consisting of europium (Eu), gadolinium (Gd), and dysprosium (Dy). The second region is amorphous or polycrystalline and includes, on the second plane, a first portion extending in a first direction parallel to the first plane and extending in a second direction, which is different from the first portion and parallel to the first plane and intersects the first direction. In the oxide superconducting layer, the volume percentage of the second region is between 0.001% and 1.10%.

[0322] The oxide superconductor of the second embodiment differs from the oxide superconductor of the first embodiment in that it requires three types of rare earth elements instead of four. Some descriptions that overlap with the first embodiment may be omitted below.

[0323] The oxide superconductor of the second embodiment is a superconducting wire. The oxide superconductor of the second embodiment has a structure similar to the oxide superconductor of the first embodiment shown in Figure 1. As shown in Figure 1, the oxide superconductor of the second embodiment comprises a substrate 10, an intermediate layer 20, an oxide superconducting layer 30, and a metal layer 40.

[0324] The oxide superconducting layer 30 of the second embodiment includes a main region 30a and a sub-region 30b. The main region 30a is an example of a first region. The sub-region 30b is an example of a second region. The main region 30a has superconducting properties. The sub-region 30b does not have superconducting properties.

[0325] The main region 30a contains rare earth elements, barium (Ba), and copper (Cu). The rare earth elements include a first element which is praseodymium (Pr), a second element selected from the group consisting of yttrium (Y), europium (Eu), gadolinium (Gd), dysprosium (Dy), holmium (Ho), and erbium (Er), and a third element selected from the group consisting of yttrium (Y), dysprosium (Dy), holmium (Ho), and erbium (Er), where the first, second, and third elements are all different elements.

[0326] If the second element is not yttrium (Y), the atomic number of the second element is less than the atomic number of the third element. Also, if the second element is yttrium (Y), the third element is at least one element selected from the group consisting of erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu). Also, if the third element is yttrium (Y), the second element is at least one element selected from the group consisting of europium (Eu), gadolinium (Gd), and dysprosium (Dy).

[0327] The first element included in the main region 30a is so-called PA (Pinning Atom), the second element is so-called MA (Matrix Atom), and the third element is so-called CA (Counter Atom). This differs from the main region 30a of the first embodiment in that it does not necessarily include an element corresponding to SA (Supporting Atom).

[0328] The oxide superconducting layer 30 of the second embodiment includes so-called second-generation clustered atom replacement artificial pins (2nd-CARPs). A first element, PA, and a third element, CA, form the CARPs.

[0329] In the main region 30a, the ratio of the atomic concentration of the second element to the sum of the atomic concentrations of the first element, the second element, and the third element is, for example, 60% or more and 95% or less.

[0330] The main region 30a contains, for example, fluorine (F). The atomic concentration of fluorine (F) in the main region 30a is, for example, 2.0 × 10⁻⁶. １５ atoms / cm ３ The above 5.0 x 10 １９ atoms / cm ３ The following applies:

[0331] The main region 30a contains, for example, carbon (C). The atomic concentration of carbon (C) in the main region 30a is, for example, 1.0 × 10⁻¹⁴. １７ atoms / cm ３ The above 5.0 x 10 ２０ atoms / cm ３ The following applies: The fluorine and carbon contained in the main region 30a are residual elements resulting from the deposition of the oxide superconducting layer 30 by the TFA-MOD method. The fluorine and carbon in the main region 30a are present, for example, in the low-angle grain boundaries 30x of the main region 30a.

[0332] The fluorine contained in the oxide superconducting layer 30 is, for example, 2.0 × 10 １６ atoms / cm ３ That concludes the explanation. Furthermore, the amount of carbon contained in the oxide superconducting layer 30 is, for example, 1.0 × 10 １８ atoms / cm ３That's all.

[0333] The configuration of the sub-region 30b of the oxide superconducting layer 30 in the second embodiment is the same as the configuration of the sub-region 30b of the oxide superconducting layer 30 in the first embodiment.

[0334] As described above, according to the second embodiment, an oxide superconductor with improved properties in a magnetic field and a method for manufacturing the same can be provided.

[0335] The following describes some examples.

[0336] A key aspect of the oxide superconductor of this embodiment is reducing the amount of QFG, which hinders the effectiveness of CARP. Reducing the amount of QFG not only reduces decomposition products of the raw material acetate, but also prevents the formation of decomposition products in each process. Before applying the manufacturing method of this embodiment, the amount of QFG could only be reduced to 1.14%, but using the manufacturing method of this embodiment, it can be reduced to 1.10% or less.

[0337] This specification clarifies the definition of impurity content. In the inventors' previous patent application, they simply stated the 99% barium acetate content as described by the vendor. This impurity content was measured using methods such as the difference finite method. However, there is no way to accurately determine the purity of barium acetate, which does not contain crystal water, and it is likely that this impurity content of barium acetate differed from the impurity content of barium acetate used in experiments.

[0338] The barium acetate manufacturer may have measured its purity immediately after manufacturing and stated it as 99%. However, while barium acetate should be colorless and transparent, in powder form it is all opaque white, and even in pellet form, colorless and transparent barium acetate is almost nonexistent. It is almost entirely opaque white.

[0339] When the barium acetate was dissolved and the remaining precipitate was measured, it was found to be 3.0% BaCO3. ３ It was found that impurities were present, and the purity was only 97.0%. Unless the other raw materials are crystalline acetates, the amount of impurities is unlikely to match the vendor's description.

[0340] Therefore, in this specification, the impurities of all acetate raw materials other than barium acetate are calculated as amounts derived from the water of crystallization obtained by thermal analysis. For copper acetate and other materials with a stable water of crystallization number, the amount of impurities can be measured from the water of crystallization number. This is because, if decomposed copper oxide (CuO) is present, the more decomposition products there are, the smaller the weight loss will be in order to avoid losing water of crystallization during thermal analysis.

[0341] While salts with a stable number of water molecules, such as copper acetate, are suitable, yttrium acetate has a water molecule count of around 3.7, which is less than 4.0, making it difficult to measure the amount of impurities. In such cases, the water molecule count was determined using a perfectly crystalline raw material, and the decrease from that amount was considered the amount of decomposition products. The crystalline raw material was prepared by sandwiching it between glass plates during thermal analysis to create a powder, which was then measured. Although the surface of the acetate may be degraded, the powder obtained from large crystals is thought to contain only decomposition products attached to the surface. The amount of these decomposition products was calculated, and the minimum impurity amount was set at 0.2%.

[0342] The process of synthesizing solutions from these acetates is the conventional YBa ２ Cu ３ O ７－ｘ This is the same as when forming YBa. This synthesis process is originally YBa ２ Cu ３ O ７－ｘ Although it was made for this purpose, the amount of CARP element is at most 40%, and the decomposition behavior is expected to show the average behavior of each acetate. Therefore, even if CARP element is present, currently YBa ２ Cu ３ O ７－ｘ It appears that no problems have occurred with the same synthesis process.

[0343] The phenomenon in which the decomposition behavior is the average behavior of each acetate salt is PrBa ２ Cu ３ O ７－ｘ This is the same discovery as the invention of the pin. Easily disassembled PrBa ２ Cu ３ O ７－ｘ In creating it, initially YBa ２ Cu ３ O ７－ｘ PrBa inside２ Cu ３ O ７－ｘ The experiment was conducted after confirming that the substance did not decompose by using concentrations of 3% and 10%. PrBa ２ Cu ３ O ７－ｘ Although it is a substance that easily decomposes due to its large ionic radius in its elemental form, after that, PrBa ２ Cu ３ O ７－ｘ Mixed solutions with concentrations of 22% and 24% have been achieved.

[0344] The resulting coating solution is used to deposit films using dip coating or spin coating methods. The film deposition process is the same as conventional methods. It is known that the film deposition conditions change depending on the concentration and viscosity of the solution.

[0345] Even if the CARP element makes up the maximum 40%, it will only be present at the Y site, and the Y site itself accounts for only 1 / 6 of all metal element sites. In other words, even with the maximum amount of CARP element mixed in, it will only occupy 8.33% of the total metal elements.

[0346] After film formation, a calcination process is immediately carried out to avoid moisture absorption and obtain a calcined film. This process is currently also YBa ２ Cu ３ O ７－ｘ It is identical to YBa during calcination. ２ Cu ３ O ７－ｘ The decomposition temperature is thought to be mainly between 210 and 240°C. Light rare earth elements, which have a large atomic radius and are unstable, decompose easily, while heavy rare earth elements, which have a small atomic radius and are stable, decompose difficult. CARP is a combination of light and heavy rare earth elements, with CARP elements present in a maximum ratio of only 8.33%. The decomposition behavior is determined by the average value of easily decomposed and difficult-to-decompose substances, so currently YBa ２ Cu ３ O ７－ｘ The calcination process has been implemented and no problems have occurred. However, in the future, the optimal value in a strict sense will be YBa ２ Cu ３ O ７－ｘ It is possible that it is slightly different from the superconducting film deposition process.

[0347] Regarding the proportion of CARP elements in the Y site, 8%, 12%, and 16% are likely to be frequently used. Proven wire materials include Dy ２ O ３ While it is stated that the percentage is 15%, from that perspective, 16% may be adopted. In that case, since Y-site accounts for 1 / 6, 2.67% of all metallic elements would be CARP elements.

[0348] The CARP structure is stable. Therefore, materials with a CARP element occupying 16% to 40% of the Y site may be primarily used in the future. However, if the proportion exceeds 40%, it becomes difficult to be certain which elements are forming the cluster. This is because the quantity is too large, and the elements may become random before forming a cluster.

[0349] The resulting calcined film is then subjected to final calcination under humidification conditions, the same as in the conventional process. The optimal oxygen partial pressure during final calcination depends on the matrix element species. YBa ２ Cu ３ O ７－ｘ If so, the oxygen partial pressure at 800°C is 1,000 ppm, but SmBa ２ Cu ３ O ７－ｘ Then it becomes 20 ppm. It also depends on the firing temperature, and the optimal oxygen partial pressure is halved for every 25°C decrease in firing temperature. In other words, YBa ２ Cu ３ O ７－ｘ In that case, the partial pressure of oxygen at 775°C and 750°C would be 500 ppm and 250 ppm, respectively.

[0350] It has long been known that the dependence of the optimal oxygen partial pressure during firing on the firing temperature behaves the same as that of YBCO, as described above, even when the matrix element species change.

[0351] Following the main firing process, pure oxygen annealing is performed. Pure oxygen annealing is performed using YBa. ２ Cu ３ O ７－ｘ So, starting from 525°C, to prevent Ba substitution, NdBa ２ Cu ３ O ７－ｘ Ya SmBa ２ Cu ３ O ７－ｘSo we start at 325°C or 375°C.

[0352] Let's assume that a system containing the element CARP is annealed with pure oxygen starting at 525°C. If the matrix element is Y, then Pr, Nd, and Sm will be present within the CARP. Pr is already present at 525°C. ３＋ →Pr ４＋ It is thought that this is the case. If Pr is uniformly dispersed within YBCO, it is known to cause a five-fold degradation phenomenon. If Pr is uniformly dispersed within YBCO, it will be present at the Y site, and it is thought that it will make the adjacent Y non-superconducting through valence change and physical contraction. At that time, Nd and Sm may be substituted with Ba. Even if Nd and Sm are substituted with Ba, there are many non-superconducting unit cells inside the CARP structure, so it is thought that there is no difference from the case where Ba substitution does not occur.

[0353] The key point of this embodiment appears to be crystalline barium acetate. It is known that even if the raw materials are not entirely crystalline, but partially degraded, QFG is suppressed and CARP is formed. However, it is unlikely that anyone would use partially degraded raw materials knowing that it would reduce superconductivity.

[0354] By using crystalline raw materials, including barium acetate monohydrate, the resulting CARP exhibits its full potential. The artificial pins capture quantum magnetic flux, mitigating the degradation of its properties in a magnetic field.

[0355] Observing structures with reduced QFG using cross-sectional TEM or Planview TEM each time is time-consuming, expensive, and cumbersome, hindering research and development. Therefore, it was discovered that identifying characteristics related to the QFG structure allows for development based on those characteristics.

[0356] When the structure formed by the TFA-MOD method is observed from the top of the substrate, it can be seen that it is an aggregate of unit cells with a size of 50 x 200 nm or slightly larger. Since the amorphous layer is formed along the boundary, the superconductivity at 77 K, for example, when the diameter is 50 nm, tends to improve.

[0357] The artificial pins that are effective at 77K exist in a way that overlaps with a portion of the 50 nmΦ quantum magnetic flux. Therefore, if this structure is cooled to 30K, multiple 5 nmΦ quantum magnetic fluxes enter the QFG, and the ends easily slip out, thus reducing the effectiveness of the artificial pins.

[0358] Conversely, if the structure presented in the embodiment is realized, the above-mentioned QFG amount is reduced, and the effect as an artificial pin at 77K becomes smaller. Therefore, if a structure with a reduced QFG amount is realized, the high magnetic field characteristics at 77K will be lower compared to structures with a large QFG amount other than those in the embodiment.

[0359] By utilizing this trend and examining the characteristics of 77K at 0.5T, 2T, 3T, and 5T, it is possible to determine whether the structure of the embodiment that suppresses QFG formation has been realized. While the structure of the embodiment can certainly be confirmed by direct observation, there are aspects where indirectly investigating QFG formation and conducting development is more effective, and such methods are also disclosed in this specification.

[0360] (Comparative Example 1) The coating solution of Comparative Example 1 was synthesized and purified according to the flowchart shown in Figure 5 to obtain the solution. In order to reduce the amount of QFG formation, crystallization raw materials were used for all acetates, with the exception of crystalline barium acetate, which was not available previously. Thermal analysis by the number of water molecules in crystallization revealed that the purity of praseodymium acetate was 99.4%, samarium acetate was 99.4%, yttrium acetate was 99.8%, copper acetate was 99.8%, and thulium acetate was 99.8%.

[0361] The barium acetate used did not have a hydrate, and the purity stated on the chemical bottle was 99%. However, it was opaque white, and barium acetate was found to be CO2 in the atmosphere. ２ It absorbs gas and produces opaque white BaCO3 ３ It appears that this is the case. Impurity analysis during dissolution showed a purity of 95.5%. Barium acetate, which does not contain water of crystallization, does not show any change even when heated up to the maximum temperature of the measuring device, 1,200°C. Therefore, the purity of barium acetate, which does not contain water of crystallization, cannot be evaluated using thermogravimetric analysis.

[0362] Praseodymium acetate, samarium acetate, thulium acetate, yttrium acetate, barium acetate, and copper acetate are mixed in a metal ion molar ratio of 2:2:4:92:200:300, dissolved in ion-exchanged water, and an equimolar amount of CF is reacted. ３ COOH was mixed and stirred to obtain the solution ref-1-ini-Sol (initial solution in Comparative Example 1).

[0363] The resulting mixed solution was placed in a round-bottom flask, and the reaction and purification were carried out under reduced pressure in a rotary evaporator for 12 hours to obtain a translucent blue substance ref-1-blue-Mat-i (the blue substance of Comparative Example 1: with a higher amount of impurities). The obtained substance ref-1-blue-Mat-i contains approximately 7 wt% water and acetic acid, which are reaction byproducts during solution synthesis. The translucent blue substance ref-1-blue-Mat-i was dissolved in 20 times its weight of anhydrous methanol to obtain the solution ref-1-MeOH-Sol-i (the methanol solution of Comparative Example 1: with a higher amount of impurities).

[0364] The purification process shown in Figure 5h is performed. Further purification of the methanol solution ref-1-MeOH-Sol-i yields a translucent blue substance ref-1-blue-Mat. In this substance, the amount of water and acetic acid has been largely replaced by methanol. This method is a patented method previously registered as the Solvent-Into-Gel method, and uses a method reported in the literature (T. Araki and I. Hirabayashi, Supercond. Sci. Technol. 16 (2003) R71-R94). The methanol contained within dissolves, and since the amount of impurities does not increase even when a methanol solution is formed, the purity is greatly improved.

[0365] The obtained translucent blue substance ref-1-blue-Mat was dissolved in a volumetric flask to a metal ion concentration of 1.50 mol / l to obtain the coating solution ref-1-CS (coating solution of Comparative Example 1).

[0366] Using the coating solution ref-1-CS and the spin coating method, a 10 × 28 × 0.50 mmt layer of LaAlO was coated at an acceleration of 10,000 rpm / s, a maximum rotation speed of 2,000 rpm, and a holding time of 60 s. ３(100) A film was formed on an oriented single crystal to obtain a translucent blue gel film ref-1-gel-film (the gel film of Comparative Example 1). As shown in Figure 6, this is part of the process of obtaining a gel film from a coating solution, decomposing organic matter in a primary heat treatment to form a calcined film, and then obtaining a superconducting film through a secondary heat treatment and pure oxygen annealing.

[0367] The obtained gel film ref-1-gel-film was immediately placed in a furnace filled with drying gas, and organic matter was decomposed at X at 200-250°C according to the profile shown in Figure 7. The residue was removed at Y and Z at temperatures below 400°C to obtain a translucent brown calcined film ref-1-cal-film (calcined film of Comparative Example 1).

[0368] The calcined film ref-1-cal-film was calcined at 750°C in a 250 ppm oxygen-mixed argon gas using the calcination profile shown in Figure 8, resulting in the oxide thin film ref-1-oxide-YBa. ２ Cu ３ O ６．００ (In comparative example 1, the matrix is ​​YBa ２ Cu ３ O ６．００ ) was obtained.

[0369] Oxide thin film ref-1-oxide-YBa ２ Cu ３ O ６．００ The CARP element-containing superconducting film ref-1-CARP-YBa is produced by annealing with pure oxygen at a temperature of 525°C or lower, and the oxygen count is treated to maximize the superconducting properties. ２ Cu ３ O ６．９３ (The superconducting film of Comparative Example 1) was obtained.

[0370] Figure 15 shows the XRD measurement results of the superconducting film of Comparative Example 1. CARP-containing superconducting film ref-1-CARP-YBa ２ Cu ３ O ６．９３ Figure 15 shows the results of the XRD measurement using the 2θ / ω method. In Figure 15, the horizontal axis represents the 2θ angle, and the vertical axis represents the intensity on a logarithmic scale. The sample was a relatively low-temperature 750°C calcined sample, but from Figure 15, YBa ２ Cu ３ O ６．９３It can be seen that a peak (00n) is obtained. Since the figure is a logarithmic graph, the peak located near the Back Ground (BG) is a fairly small peak.

[0371] In Figure 15, the angles around 24 degrees and 48 degrees in 2θ are LaAlO ３ These are the (100) and (200) peaks on the substrate. The strongest peak, YBa, is visible at approximately 46.8 degrees in 2θ. ２ Cu ３ O ６．９３ (006) This is the peak. The peak intensity is 311,000 cps, which is a good peak intensity for a 220 nm thick superconductor fired at 750°C.

[0372] In Comparative Example 1, the anomaly in the 2θ / ω method of XRD measurement is Y, which appears around 34 degrees. ２ O ３ And Ba can be seen at around 42 degrees. ２ CuO ３ That is. Y ２ O ３ The peak intensity of is 180 cps, and the nearby BG is 100 cps, therefore Y ２ O ３ The intensity for that minute would only be 80 cps.

[0373] Ba visible at around 42 degrees ２ CuO ３ The intensity is only 200 cps, and even in this area BG is 100 cps, Ba ２ CuO ３ The intensity would be only 100 cps. ref-1-CARP-YBa ２ Cu ３ O ６．９３ (006) The peak is 311,000 cps, and even after subtracting the background, it remains almost the same value. Therefore, when comparing the intensity of the other phase with the main peak, it is 100 / 310,900. The intensity ratio is 0.03%, which is so small that it can be almost ignored.

[0374] Figure 16 shows the ω-scan measurement results for the superconducting film of Comparative Example 1. Figure 16 shows the ω-scan results using the (006) peak of Comparative Example 1. This sample was fired at a relatively low temperature of 750°C, and the unit cell bonding is weaker compared to the sample fired at 800°C. As a result, an intensity of about 200 cps is observed even at a distance from the center, for example, at ω = 20 degrees. Since the background is 100 cps, the signal is only 100 cps.

[0375] However, a signal of 100 cps at ω = 20 degrees is a sufficiently small value considering that it is a low-temperature charring process at 750°C. The smaller this value, the stronger the bond between the unit cells or the smaller the average bond angle at the low-angle grain boundaries. This improves the superconducting properties.

[0376] Superconducting film ref-1-CARP-YBa ２ Cu ３ O ６．９３ The superconductivity properties were measured in liquid nitrogen under its own magnetic field using the induction method. In principle, the induction method requires the presence of superconductors in a region of approximately 6 mm in diameter within the superconducting film to be evaluated. Therefore, characteristics are obtained only at 4-6 points in the central region, but the highest value among these points is considered the characteristic of the superconducting film. The obtained superconductivity property was 3.58 MA / cm². ２ The result was (77K, 0T). This result is shown in Table 1.

[0377]

[0378] LaAlO ３ The properties degrade due to the formation of a / b axis-oriented particles on the substrate, so the properties also depend on the film thickness. The film thickness of this sample is 220 nm, and typically, when fired at 800°C, the film thickness is 5.5 MA / cm. ２ Characteristics around (77K, 0T) can be obtained. Compared to those characteristics, Comparative Example 1 appears to have sufficiently high characteristics.

[0379] Superconductor J ｃ The values ​​tend to decrease with lower firing temperatures, which is thought to be due to increased loss at low-angle grain boundaries between unit cells. For a 750°C fired sample, the value was 3.58 MA / cm². ２The superconducting properties at (77K, 0T) were good, and XRD measurements also showed minimal dissimilar phases. This sample was expected to show improved superconducting properties in a magnetic field due to the formation of CARP.

[0380] This sample was masked with chemical-resistant tape and etched with a dilute acetic acid solution to create a sample with a bridge section approximately 2 mm wide, enabling four-terminal measurement. The current and voltage terminals of the sample were coated with Pt by sputtering, and contact with the sample was improved by pure oxygen annealing.

[0381] Figure 17 shows the J of the examples and comparative examples. ｃ - This is an explanatory diagram for B-T measurement. Figure 17 shows the measurement sample attached to the probe. ｃ - This shows the state immediately before the B-T measurement is performed.

[0382] The white area in the center of the diagram is a ceramic attached to the probe. A 5mm wide metal plate, designed to conduct 100A of current, has a 4mm wide silver tape attached to it. The silver tape connects to an electronic load device. The silver tape is folded over to relieve stress.

[0383] The sample is attached slightly to the right of the current terminal, and the electrical connection between the sample and the Pt electrode is maintained with indium silver solder at the Pt electrode deposition site. The thin black and white terminal wires visible at the top of the sample are the voltage terminals. The voltage terminals pick up the voltage generated in the bridge section visible between the voltage terminals, which is 2 mm wide and 10 mm long. J ｃ The judgment criterion was determined using the common value of 1 μV / cm. The sample was heated to 77K–20K and 0–5T. ｃ Measurements were taken, and at 30K, J was measured from 0 to 15T. ｃ Measurements were taken.

[0384] Figure 18 shows the J of Comparative Example 1. ｃ This figure shows the measurement results of the B-T measurement. In Figure 18, the horizontal axis is the magnetic field strength in tesla (T), and the vertical axis is the logarithmic scale in joules (J). ｃ Value, MA / cm ２ The circles in the figure represent the data for Comparative Example 1. On the other hand, the squares in the figure represent the data for Comparative Example 0 (zero), which is used for comparison. Comparative Example 0 does not include CARP. ２ Cu ３O ６．９３ That is the case.

[0385] Comparing the characteristics at 30K and 5T, the characteristic of Comparative Example 0 is 1.07 MA / cm ２ (30K, 5T) is the case for Comparative Example 1, while Comparative Example 1 is 1.02 MA / cm². ２ (30K, 5T). They have almost the same characteristics.

[0386] From the 30K data in Figure 18, at 5T, the characteristics of Comparative Example 1 are almost the same as those of Comparative Example 0, while at 1T, 0.5T, and 0.2T, YBa ２ Cu ３ O ６．９３ It can be seen that it becomes even smaller. If CARP were formed in Comparative Example 1, the lower the magnetic field where the quantum magnetic flux decreases, the greater the quantum magnetic flux pinning effect by CARP would be, and it should have better performance than Comparative Example 0, which does not have CARP. In other words, this indicates that Comparative Example 1 does not have a structure that pins the quantum magnetic flux at low temperatures and low magnetic fields.

[0387] On the other hand, at 77K, the characteristics of Comparative Example 0 are displayed up to 3T, where 0.020 MA / cm² is shown. ２ (77K, 3T). In contrast, Comparative Example 1 showed 0.065 MA / cm². ２ (77K, 3T) is nearly three times the original value.

[0388] The results above indicate that while there is no effect in pinning the 5 nmΦ quantum magnetic flux at 30 K, there is some structure in Comparative Example 1 that pins the 50 nmΦ quantum magnetic flux at 77 K. As explained at the beginning, there is theoretically no artificial pin that is effective in both 30 K and 77 K magnetic fields. The results in Figure 18 indicate that Comparative Example 1 is a superconductor that has some structure that is effective at 77 K.

[0389] Cross-sectional TEM observation of Comparative Example 1 revealed a large number of c-axis oriented particles, similar to those observed in numerous samples previously. This result could easily be inferred from the good XRD measurement results and excellent superconducting properties obtained by CryoScan, even without performing this TEM observation. However, if that were the case, then CARP should have formed inside Comparative Example 1, improving its properties in a magnetic field.

[0390] J at 30K ｃ -B-T characteristics did not improve at 77K J ｃ To investigate the reason for the improved B-T characteristics, a Planview TEM observation was performed. The results are shown in Figures 14(a) and 14(b), which were previously shown. In Figures 14(a) and 14(b), because the firing was performed at 750°C, the mobility of the pseudo-liquid phase is reduced, resulting in a slightly distorted unit cell assembly.

[0391] Numerous white structures, indicated by arrows, are visible at the boundaries of the unit cell aggregate. These structures were amorphous. However, cross-sectional TEM and X-ray diffraction revealed that not the entire structure was amorphous; approximately 15% of the upper portion was amorphous. In other words, as shown in Figure 13(b), an orientation layer exists beneath the amorphous region, and the amorphous region is concentrated near the surface of the film, as seen in Figures 14(a) and 14(b).

[0392] Observation of the cross-sectional TEM image of the amorphous region revealed that the depth of the amorphous region at that point was approximately 15% of the superconducting film thickness. Since this sample is 220 nm thick, the depth of the amorphous region is approximately 33 nm. This depth will likely vary depending on the measurement location and there is no guarantee that it will be constant. It is also unclear whether this value is an average, but when measured at only three points, the values ​​were 33 nm, 31 nm, and 35 nm, so the median depth of the amorphous layer was 33 nm.

[0393] In Figures 14(a) and 14(b), the white areas appear to have a width of approximately 3–7 nm, but the areas with a thin amorphous layer do not appear white, so the actual width is 5–10 nm.

[0394] Assuming a median width of 5 nm for the range of 3-7 nm, and a median spacing of 40 nm between amorphous regions, the area percentage of amorphous regions is 12.5%. Although the spacing is narrower in some areas and wider in others, the median area percentage of amorphous regions appears to be 12.5%.

[0395] In the above case, since the volume is 15% in the thickness direction and 12.5% ​​in the width direction, the volume percentage of the amorphous region in the oxide superconducting layer is calculated to be 1.87%. If the amorphous region is formed by impurities in the oxide superconducting layer, this result is larger than the value calculated assuming the amount of impurities in the raw materials is 5.0% barium acetate, 0.3% praseodymium acetate, 0.3% samarium acetate, and 0.1% others. This is the same result as assuming a higher proportion of other decomposition products, around 0.3-0.5%. The reason why there were more decomposition products than calculated is thought to be that the calcination and final calcination processes deviated from the optimal conditions, resulting in an increase in non-uniform phases. As a result, it is thought that an amorphous layer of 1.87% on average was formed.

[0396] As described above, the volume percentage of the amorphous region in Comparative Example 1 is only 1.87%. However, as can be seen in Figures 14(a) and 14(b), an amorphous region with a width of 5 nm is formed, and since it has a depth of 15%, the quantum magnetic flux enters the amorphous region more easily than in CARP, which has a potential of only 8% reduction.

[0397] Figures 19 and 20 are explanatory diagrams of the quantum magnetic flux state of Comparative Example 1. Figure 19 is a schematic diagram showing a cross-section of the superconducting film of Comparative Example 1. Figure 20 is a schematic diagram showing the top surface of the superconducting film of Comparative Example 1. Figures 19 and 20 are diagrams showing the distribution of CARP and QFG within the superconducting film of Comparative Example 1.

[0398] Figure 19 shows the case where the depth of the QFG is 15% of the thickness of the superconducting film. In this case, the quantum magnetic flux enters the QFG. When the quantum magnetic flux enters this QFG, as shown in Figure 20, the quantum magnetic flux moves in the direction of the applied stress. Then, another quantum magnetic flux enters and moves along the same path, so the stress on the quantum magnetic flux at the end of the QFG exceeds the pinning force and enters the superconducting layer region. Therefore, even if CARP is formed in the superconducting film, the magnetic field performance at 20-30K does not improve.

[0399] The structure described above is a structure worthy of being called a quantum magnetic flux gallery, as the quantum magnetic flux moves through it as if observing it. If this QFG is present, even if CARP is formed inside, the effect of improving the magnetic field characteristics cannot be obtained because the quantum magnetic flux passes through the QFG. However, if the amount of QFG is reduced, the effect of CARP can be exerted. In other words, it is preferable to reduce the volume ratio of the QFG to the superconducting film to less than 1.87%.

[0400] The above QFG cannot exert the effect of CARP even at a volume percentage of 1.87%. The volume percentage of QFG required to exert the effect of CARP is a level that cannot be achieved with coating solutions made at the 98% or 99% purity levels listed on the chemical manufacturers' products.

[0401] Therefore, to form a superconducting film that can exert the effects of CARP, a crystalline raw material with a higher purity is required. Because the inside of the crystal is not exposed to the outside air, degradation of the crystalline raw material is gradual. In addition, even if degradation occurs in the crystalline raw material, the surface layer degrades and discolors first, making it easy to notice, and the degradation volume is small, so the impact is also small. A purity of 99.8% can be achieved with crystalline raw materials. It is thought that crystalline raw materials with a purity of 99.8-100.0% also exist. However, since the purity resolution of the results of precise thermal analysis is 0.2%, it is stated as 99.8% here.

[0402] Praseodymium acetate is Pr ３＋ →Pr ４＋ And it changes, and samarium acetate becomes Sm ３＋ →Sm ２＋ It changes into a different form and deteriorates from the inside. Therefore, achieving a purity of 99.8% is difficult, and it tends to be around 99.4%. In Comparative Example 1, the commercially available crystalline raw materials are five types other than Ba. However, as the experimental results show, if the barium acetate deteriorates, QFG is formed and CARP does not exert its effect.

[0403] The purity of the raw materials used in Comparative Example 1 was 99.4% for praseodymium acetate (crystalline raw material), 99.4% for samarium acetate (crystalline raw material), 99.8% for yttrium acetate (crystalline raw material), 99.8% for copper acetate (crystalline raw material), and 99.8% for thulium acetate (crystalline raw material). In addition, barium acetate, which could not be measured by thermal analysis and had a purity of 95.5% in a dissolution test, was used. The total amount of impurities in the raw materials was calculated to be 1.64%, as shown in Table 2.

[0404]

[0405] The impurity amount of 1.87% estimated from amorphous regions observed using Planview TEM and cross-sectional TEM is slightly higher than the impurity amount of 1.64% calculated from the raw materials. While the expected impurity amount may differ depending on the observation area, the amount of impurities will increase if the subsequent film deposition, calcination, final calcination, and oxygen annealing processes deviate from the optimal value. The increased amount of impurities should form QFGs through growth according to the pseudo-liquid phase network model, so 1.87% is not inconsistent.

[0406] The above results indicate that barium acetate must also be a crystalline raw material. Before that, however, in order to confirm that QFG originates from impurities in the raw material, we decided to investigate this in the following Comparative Example 2.

[0407] (Comparative Examples 2A and 2B) Two types of coating solutions for Comparative Example 2 were prepared according to the flowchart shown in Figure 5. These solutions used praseodymium acetate with a purity of 99.4%, samarium acetate with a purity of 99.4%, yttrium acetate with a purity of 99.8%, copper acetate with a purity of 99.8%, and thulium acetate with a purity of 99.8%, calculated from the number of water crystals obtained by thermal analysis. They also used powdered barium acetate ref-2-new-BaOAc (new barium acetate for Comparative Example 2A), which was purchased new but stored for about a year, and barium acetate ref-2-old-BaOAc (old barium acetate for Comparative Example 2B), which was kept for two years after opening.

[0408] Barium acetate ref-2-new-BaOAc and ref-2-old-BaOAc were dissolved and filtered, and the amount of barium carbonate was found to be 3.0% and 6.5%, respectively. The impurity amounts of each acetate are shown in Table 2.

[0409] Praseodymium acetate, samarium acetate, thulium acetate, yttrium acetate, barium acetate, and copper acetate are mixed in a metal ion molar ratio of 2:2:4:92:200:300, dissolved in ion-exchanged water, and an equimolar amount of CF is reacted. ３ COOH was mixed and stirred to obtain solutions ref-2-ini-Sol-new and ref-2-ini-Sol-old.

[0410] A solution ref-2-ini-Sol-new (coating solution of Comparative Example 2A) was obtained using barium acetate ref-2-new-BaOAc, and a solution ref-2-ini-Sol-old (coating solution of Comparative Example 2B) was obtained using barium acetate ref-2-old-BaOAc.

[0411] The obtained solutions ref-2-ini-Sol-new and ref-2-ini-Sol-old were placed in eggplant-shaped flasks, and the reaction and purification were carried out under reduced pressure in a rotary evaporator for 12 hours to obtain the translucent blue substances ref-2-Mat-new-i (substance of Comparative Example 2A: with a higher amount of impurities) and ref-2-Mat-old-i (substance of Comparative Example 2B: with a higher amount of impurities), respectively.

[0412] The obtained substances ref-2-Mat-new-i and ref-2-Mat-old-i contain approximately 7 wt% water and acetic acid, which are reaction byproducts during solution synthesis. The translucent blue substances ref-2-blue-Mat-i-new and ref-2-blue-Mat-i-old were dissolved in 20 times their weight in anhydrous methanol to obtain the solutions ref-2-MeOH-Sol-new (methanol solution of Comparative Example 2A) and ref-2-MeOH-Sol-old (methanol solution of Comparative Example 2B), respectively.

[0413] The purification process shown in Figure 5h is performed. Further purification of the methanol solutions ref-2-MeOH-Sol-new and ref-2-MeOH-Sol-old yields the translucent blue substances ref-2-blue-Mat-new (substance of Comparative Example 2A) and ref-2-blue-Mat-old (substance of Comparative Example 2B). These solutions have significantly reduced impurities such as water and acetic acid.

[0414] The obtained translucent blue substances ref-2-blue-mat-new and ref-2-blue-mat-old were dissolved in a volumetric flask to a metal ion concentration of 1.50 mol / l to obtain coating solutions ref-2-CS-new (coating solution of Comparative Example 2A) and ref-2-CS-old (coating solution of Comparative Example 2B), respectively.

[0415] Using the coating solutions ref-2-CS-new and ref-2-CS-old, a spin coating method was used to produce 10 × 28 × 0.50 mmt of LaAlO at an acceleration of 10,000 rpm / s, a maximum rotation speed of 2,000 rpm, and a holding time of 60 s. ３ (100) A film was formed on an oriented single crystal to obtain a translucent blue gel film ref-2-gel-film-new (gel film of Comparative Example 2A) and a translucent blue gel film ref-2-gel-film-old (gel film of Comparative Example 2B).

[0416] The obtained gel films ref-2-gel-film-new and ref-2-gel-film-old were immediately placed in a furnace filled with drying gas, and organic matter was decomposed at X at 200-250°C according to the profile shown in Figure 7. The residue was removed at Y and Z below 400°C, yielding translucent brown calcined films ref-2-Cal-new (calcined film of Comparative Example 2A) and ref-2-Cal-old (calcined film of Comparative Example 2B).

[0417] The calcined films ref-2-cal-film-new and ref-2-cal-film-old were calcined at 750°C in 250 ppm oxygen-mixed argon gas using the calcination profile shown in Figure 8, resulting in the oxide thin film ref-2-oxide-YBa. ２ Cu ３ O ６．００-new (YBa of Comparative Example 2A) ２ Cu ３ O ６．００ ), and oxide thin film ref-2-oxide-YBa ２ Cu ３ O ６．００ -old (YBa of Comparative Example 2B) ２ Cu ３ O ６．００ ) was obtained.

[0418] Oxide thin film ref-2-oxide-YBa ２ Cu ３ O ６．００ -new, and ref-2-oxide-YBa ２ Cu ３ O ６．００ -old then undergoes pure oxygen annealing, and the oxygen count is processed to maximize the superconducting properties, resulting in the superconducting film ref-2-CARP-YBa ２ Cu ３ O ６．９３ -new (superconducting film of Comparative Example 2A), and ref-2-CARP-YBa ２ Cu ３ O ６．９３ -old (the superconducting film of Comparative Example 2B) was obtained for each.

[0419] Figure 21 shows the XRD measurement results of the superconducting film of Comparative Example 2. Superconducting film of Comparative Example 2A (ref-2-CARP-YBa ２ Cu ３ O ６．９３ -new), and the superconducting film of Comparative Example 2B (ref-2-CARP-YBa ２ Cu ３ O ６．９３ -old) was measured using the 2θ / ω method of XRD measurement. Figure 21 shows the results for the superconducting film of Comparative Example 2A. The YBa was good, almost the same as in Figure 15. ２ Cu ３ O ６．９３ It can be seen that a (00n) peak has been obtained.

[0420] Figure 21 appears to have slightly more anomalies than Figure 15. However, this intensity is only 200 cps including the background, and it is a peak that is thought to be picking up anomalies formed on the surface, so it is considered to be within the experimental error range.

[0421] The XRD measurements of the superconducting film of Comparative Example 2A and the superconducting film of Comparative Example 2B (figure omitted) show different phases using the 2θ / ω method, with the one visible around 34 degrees being Y. ２ O ３ Ba visible at around 42 degrees ２ CuO ３ It appears that both tissues have well-aligned structures.

[0422] Figure 22 shows the ω-scan measurement results for the superconducting film of Comparative Example 2. The ω-scan results using the (006) peak for the superconducting films of Comparative Example 2A and Comparative Example 2B were almost the same as those for Comparative Example 1 in Figure 16. Figure 22 shows the measurement results for the superconducting film of Comparative Example 2A, which is one of the measurement results.

[0423] Here, we can see that the intensity around ω = 20 degrees is lower compared to Comparative Example 1 in Figure 16. However, it is also true that the difference is not significant. In the current film deposition, there are sufficiently few heterogeneous phases and a good orientation structure is formed, so it is difficult to find differences in XRD measurements. For this reason, in the measurements in the following examples, the XRD measurement graphs will be omitted unless a particular difference is found.

[0424] The superconducting properties of the superconducting films of Comparative Example 2A and Comparative Example 2B were measured in liquid nitrogen under its own magnetic field using the induction method. In principle, the induction method requires the presence of a superconductor in a region of approximately 6 mm in diameter within the superconducting film to be evaluated. Therefore, only the properties of 4 to 6 points in the central region were obtained, but the highest value among these points was used to represent the characteristics of the superconducting film. The obtained superconducting properties were 3.64 and 3.90 MA / cm², as shown in Table 1. ２ The result was (77K, 0T). This also appears to be a good result.

[0425] The superconducting films of Comparative Example 2A and Comparative Example 2B were subjected to XRD measurement and Inductive J ｃ Based on the measurement results, we considered the possibility that CARP was being formed. Therefore, we formed a bridge circuit similar to Comparative Example 1, and J ｃ -B-T measurement was performed.

[0426] The obtained Jｃ Table 1 summarizes the characteristics at 77K and 30K obtained for Comparative Examples 0, 1, 2A, and 2B of the B-T measurement results. At 77K, the data from 0.5 to 5.0T showed no significant differences. YBa of Comparative Example 0 ２ Cu ３ O ６．９３ In comparison, the data for 2T, 3T, and 5T appeared to show improvement.

[0427] We believe that taking the ratio of the data makes it easier to grasp the trend of dependence on magnetic field strength, J ｃ (77K, 0.5T), J ｃ (77K, 2.0T), J ｃ (77K, 3.0T), and J ｃ We decided to compare the values ​​of α / β, α / γ, and α / δ, with (77K, 5.0T) being denoted as α, β, γ, and δ, respectively.

[0428] The α / β, α / γ, and α / δ values ​​for Comparative Example 1 are 3.4, 6.3, and 35, respectively, and the graph shows that these are smaller than the values ​​of Comparative Example 0 (5.5, 13, and 216). Comparative Example 1 has smaller values ​​compared to the case without CARP. The values ​​for Comparative Example 1, which contains the CARP element, are smaller than the values ​​for Comparative Example 0, which does not contain the CARP element.

[0429] The α / β, α / γ, and α / δ values ​​for Comparative Example 2A and Comparative Example 2B were examined. The values ​​for Comparative Example 2A were 3.5, 7.0, and 41, while the values ​​for Comparative Example 2B were 2.9, 5.3, and 20. It was found that the values ​​for Comparative Example 2A and Comparative Example 2B were close to those of Comparative Example 1.

[0430] J ｃ The numerical values ​​expressed as ratios, as discussed in Comparative Example 1, indicate that a larger value means that the QFG will be smaller and the formed CARP will exert its effect. Conversely, a smaller value means that a large amount of QFG will be formed and the effect of CARP will be lost. From the above data, it was found that the amount of QFG formed increased in Comparative Example 2B, which used old barium acetate, and decreased in Comparative Example 2A, which used new barium acetate.

[0431] To confirm the above results, we decided to perform Planview TEM observation of the superconducting film of Comparative Example 2A, which had relatively large values ​​for α / β, α / γ, and α / δ. This is because the larger values ​​suggest a decrease in the amount of QFG formation.

[0432] Figure 23 is a transmission electron microscope (TEM) image of the oxide superconducting layer of Comparative Example 2A. Figure 23 is a TEM image of the superconducting film of Comparative Example 2A. Figure 23 shows the results of Planview TEM observation. Figure 23 corresponds to Figure 14(b).

[0433] Figures 23 and 14(b) are observation images at the same 1,000,000x magnification, and the 10 nm scale in the lower left is the same. In Figure 23, it can be seen that the amorphous region, QFG, is reduced compared to Figure 14(b). The width of the amorphous region appears to be 3-5 nm. The median is estimated to be 4 nm, and from the low-magnification observation image, the median of a short piece of the unit cell aggregate is estimated to be 40 nm, suggesting that there is 10% degradation in the width direction.

[0434] The amorphous region in the film thickness direction was 12.5% ​​based on the median of three measurements. Therefore, the total amount of impurities was 1.25%. This amount of impurities is less than the 1.87% in Comparative Example 1. However, the impurities formed enough amorphous regions to inhibit the effect of CARP, and it is thought that these amorphous regions accumulated at the grain boundaries to form QFGs. For this reason, it is thought that the effect of CARP did not manifest in the superconducting film of Comparative Example 2A.

[0435] The superconducting film Comparative Example 2B, another superconducting film created in this study, has a QFG content of 2.37% calculated from the impurity content. The higher QFG content compared to Comparative Example 1B likely improved the characteristics at the 77K high magnetic field, resulting in smaller values ​​for α / β, α / γ, and α / δ. Conversely, it is thought that the QFG content prevented the improvement in characteristics at 30K.

[0436] The impurity content of Comparative Example 2A is 1.14%, as shown in the calculation results in Table 2. This amount is slightly less than the 1.25% estimated from the Planview TEM and cross-sectional TEM observations. However, similar to the sample in Comparative Example 1, the amount of heterogeneous phase may have increased due to other processes not being optimal, so this seems to be a reasonable result. In addition, the amount of amorphous material from the Planview TEM and cross-sectional TEM observations was only examined at three points each. Measuring it infinitely would also be impractical. Therefore, the substitute impurity amount calculation seems to be a reasonable result and will be useful for future reference.

[0437] Similarly, the amount of impurities in Comparative Example 2B is calculated to be 2.30% from the calculation results in Table 1. The analysis result was 2.37%, which is also a close value, but it can be seen that the analysis result is slightly higher. From the three samples in total, Comparative Example 1, Comparative Example 2A, and Comparative Example 2B, it was found that impurities in the raw material acetate were the main cause of the formation of the amorphous region, QFG.

[0438] Currently, the main topic of discussion in the superconducting field is the development of superconducting wires with improved properties at 20-30K for applications in magnetic fields. One reason for this is that using superconducting wires in a magnetic field reduces their superconducting properties due to the influence of quantum magnetic flux, so they need to be used at low temperatures where the superconducting properties can be sufficiently enhanced.

[0439] Furthermore, as explained in the basic principle of artificial pins above, at 77K the quantum magnetic flux size is 50 nmΦ, so artificial pins are ineffective in the first place. If using particulate artificial pins, only 1 / 1,000 the number can be produced compared to artificial pins with a diameter of 5 nmΦ. This is because the volume in which artificial pins can be placed is limited to 15%.

[0440] In addition, in the case of a 5 nm diameter artificial pin, the displacement distance of the quantum magnetic flux is 5 nm, and there is a difference of 50 nm, which is twice that of a 50 nm diameter artificial pin, so the pinning force is only 1 / 10. When creating artificial pins at 30 K, PLMP produces only weak artificial pins because the superconducting potential is a sparse value, but CARP, which is an SLMP, can produce ideal artificial pins. The superconducting potential changes from 0% to 100% at a position shifted by 5 nm. However, it seems difficult to create a large 50 nm diameter pin with SLMP. This is because, based on the results of investigations into past presentations, it has been found that the CARP was around 10 nm in size, and there is a problem as to how a 50 nm diameter structure can be made when the unit cell assembly is only 50 nm wide in the first place.

[0441] On the other hand, the artificial pins of this wire at 77K are Dy ２ O ３ It is approximately 50 nm in diameter, and adjacent to YBa ２ Cu ３ O ６．９３ Since it is known to be superconducting, the superconducting potential changes from 0% to 100%. However, because the distance is 50 nm, the pinning force is 1 / 10.

[0442] Considering the above points together, the pinning force of a 30K artificial pin and a 77K artificial pin should be approximately 10,000:1. This wire is likely used as an effective high-temperature superconducting wire because it can eliminate the influence of even slight magnetic fields at 77K.

[0443] From the above results, it was found that reducing the amount of impurities in barium acetate is necessary to exert the effects of CARP, which is an SLMP. In the following examples, experiments using crystalline barium acetate are conducted, and it is explained that a structure capable of exerting the effects of CARP can be realized.

[0444] (Example 1) A coating solution was prepared according to the flowchart shown in Figure 5. 99.4% pure praseodymium acetate, 99.4% pure samarium acetate, 99.8% pure yttrium acetate, 99.8% pure copper acetate, and 99.8% pure thulium acetate were used, calculated from the number of water crystals obtained by thermal analysis.

[0445] Figure 24 shows the barium acetate used when preparing the coating solution for the comparative example. The barium acetate used in the comparative example was anhydrous, and the chemical bottle indicated a purity of 99%. The barium acetate used in the comparative example was (CH ３ COO) ２ It can be written as Ba.

[0446] Some of the barium acetate has turned white, and in that part, the barium acetate has turned into carbon dioxide (CO2). ２ ) absorbs barium carbonate (BaCO3) ３ It is believed that this was the cause. It is thought that barium carbonate, an impurity, was the cause of QFG formation.

[0447] Figure 25 shows the barium acetate used to prepare the coating solution in Example 1. The barium acetate used in Example 1 is a specially ordered barium acetate monohydrate, which is a transparent, large crystal. The barium acetate used in Example 1 is (CH ３ COO) ２ Ba・H ２ It can be written as O.

[0448] The appearance of barium acetate monohydrate is as shown in Figure 25. When stored in dry argon gas, it always maintains this shape, and there is almost no change in the surface to white. The number of water molecules in crystals determined by thermal analysis is 1,000, and from this value, it can be inferred that the purity is 99.8% or higher. This purity is thought to be between 99.8% and 100.0%, but considering the resolution of thermal analysis, it is likely that a value up to 99.8% is guaranteed.

[0449] The above praseodymium acetate, samarium acetate, thulium acetate, yttrium acetate, barium acetate, and copper acetate are mixed in a metal ion molar ratio of 2:2:4:92:200:300, dissolved in ion-exchanged water, and reacted with equimolar amounts of CF. ３ The mixture was mixed with COOH and stirred to obtain the solution ex-1-MOAc-Sol (aqueous acetate solution from Example 1).

[0450] The obtained solution ex-1-Sol-MOAc was placed in a round-bottom flask, and the reaction and purification were carried out under reduced pressure in a rotary evaporator for 12 hours to obtain a translucent blue substance ex-1-blue-Mat-i (blue substance of Example 1: containing impurities).

[0451] The obtained substance ex-1-blue-Mat-i contains approximately 7 wt% water and acetic acid, which are reaction byproducts during solution synthesis. The translucent blue substance ex-1-blue-Mat-i was dissolved in 20 times its weight of anhydrous methanol to obtain a methanol solution ex-1-MeOH-Sol-i (methanol solution of Example 1: containing impurities of water and acetic acid).

[0452] The purification process shown in Figure 5h was carried out. Further purification of the methanol solution ex-1-MeOH-Sol-i yielded a translucent blue substance, ex-1-blue-Mat (the blue substance from Example 1: free of impurities). This solution had significantly reduced impurities such as water and acetic acid.

[0453] The obtained translucent blue substance, ex-1-blue-Mat, was dissolved in a volumetric flask to a metal ion concentration of 1.50 mol / l to obtain the coating solution ex-1-coating-Sol (coating solution of Example 1).

[0454] Using the coating solution ex-1-coating-Sol and the spin coating method, a 10 × 28 × 0.50 mmt layer of LaAlO was produced with an acceleration of 10,000 rpm / s, a maximum rotation speed of 2,000 rpm, and a holding time of 60 s. ３ (100) A film was deposited on an oriented single crystal to obtain a translucent blue gel film ex-1-Gel (gel film of Example 1).

[0455] The obtained gel film ex-1-Gel-film was immediately placed in a furnace filled with drying gas, and organic matter was decomposed at X at 200-250°C according to the profile shown in Figure 7. The residue was removed at Y and Z at temperatures below 400°C to obtain a translucent brown calcined film ex-1-cal-film (calcined film of Example 1).

[0456] The calcined film ex-1-oxide-Cal-film was calcined at 750°C in a 250 ppm oxygen-mixed argon gas using the calcination profile shown in Figure 8, resulting in the oxide thin film ex-1-oxide-YBa ２ Cu ３ O ６．００ (YBa of Example 1) ２ Cu ３ O ６．００ ) was obtained.

[0457] Oxide thin film ex-1-oxide-YBa ２ Cu ３ O ６．００ Next, pure oxygen annealing is performed, and the oxygen count is processed to maximize the superconducting properties, resulting in the superconducting film ex-1-CARP-YBa of Example 1. ２ Cu ３ O ６．９３ I obtained it.

[0458] The superconducting films of Example 1 were measured using the 2θ / ω method of XRD measurement. The results were almost the same as those in Figure 15, indicating good YBa. ２ Cu ３ O ６．９３ It was found that only the (00n) peak was obtained. Since no significant difference was observed, the figure is omitted. At present, QFG is mainly formed near the surface, so no difference is observed in XRD measurement, J ｃ - The difference is likely to be determined by the B-T measurement.

[0459] The XRD measurement of the superconducting film in Example 1 shows a different phase in the 2θ / ω method, with a Y-shaped phase visible around 34 degrees. ２ O ３ And Ba can be seen at around 42 degrees. ２ CuO ３ Both were small, indicating the formation of a well-oriented structure. Since this result was almost identical to that of previous superconductors, the figure is omitted.

[0460] The ω-scan results using the (006) peak of the superconducting film in Example 1 were almost identical to those in Figure 16. The difference was barely discernible in the XRD measurements. Therefore, the figure is omitted here as well.

[0461] The superconducting properties of the superconducting film in Example 1 were measured using the induction method in liquid nitrogen under its own magnetic field. In principle, the induction method requires the presence of a superconductor in a region of approximately 6 mm in diameter within the superconducting film to be evaluated. Therefore, only the properties of 4 to 6 points in the central region were obtained, but the highest value among these points was used to represent the characteristics of the superconducting film. The obtained superconducting properties are shown in Table 1, at 4.04 MA / cm². ２ (77K, 0T). This also appears to be a good result. For reference, the superconductivity characteristics of the three samples described in Comparative Example 1 and Comparative Example 2 were 3.58, 3.64, and 3.90 MA / cm². ２ (77K, 0T) is a result that is not significantly different.

[0462] XRD measurement of the superconducting film in Example 1 and InductiveJ ｃ Although the measurement results were almost identical to those of the comparative example, considering the possibility that CARP was being formed, a bridge circuit was formed in the same manner as in Comparative Example 1, and J ｃ -B-T measurement was performed.

[0463] Figure 26 shows the J of Example 1. ｃ This figure shows the measurement results of the B-T measurement. In Figure 26, the horizontal axis is the magnetic field in units of T, and the vertical axis is the logarithmic J. ｃ These are the values. Measurements were taken at 20K and 77K, with a maximum measurement force of 5T. At 30K, measurements were taken with a magnetic field applied up to a maximum of 15T.

[0464] We will first compare the data at 30K, where the quantum magnetic flux is 5 nmΦ. The characteristic at 30K and 5T is 2.11 MA / cm ２ This significantly exceeds the 1.10 of Comparative Example 0, indicating that nearly twice the performance has been achieved.

[0465] Another characteristic of the 30K data is that the degree of performance improvement is greater at lower magnetic fields compared to the superconducting film of Comparative Example 0. If CARP is present and the QFG is sufficiently small, the quantum magnetic flux decreases at lower magnetic fields, and therefore the performance degradation effect in a magnetic field is reduced. This effect can be clearly seen from the graph in Figure 26. In other words, the data in Figure 26 indicates that the superconducting film of Example 1 has formed CARP internally and that the QFG near the surface is formed to be sufficiently small.

[0466] Another notable piece of data is the 77K data. For Comparative Example 0, the superconducting film shows this data up to 3T. On the other hand, the superconducting film of Example 1 shows a decrease in performance at 77K with increasing magnetic field, becoming almost the same as Comparative Example 0 at 1.5T, and dropping significantly at 2.0T. The graph suggests that the absence of QFG reduced the magnetic field characteristics at 77K, and the characteristics became weaker at higher magnetic fields.

[0467] To investigate whether the QFG of the superconducting film in Example 1 was reduced as expected, Planview TEM observation was performed, and the results are shown in Figures 4(a) and 4(b). Because it was a low-temperature firing at 750°C, the unit cell assembly has a non-linear structure. This is because the unit cells grow in a state where the mobility of the pseudo-liquid phase is reduced, as explained earlier.

[0468] The most distinctive feature of this sample is the significant reduction in the amorphous region. As can be seen in Figures 4(a) and 4(b), the width of the amorphous region appears to be 2-3 nm, but the depth in the direction was only 7 nm at the median of the analysis at three points, which is likely why the QFG is difficult to see in Planview TEM observation. Within the unit cell assembly with a width of 30 nm, it is thought that an amorphous region with a median of 2.5 nm existed at a depth of 7 nm. The thickness of the superconducting film is 220 nm. Figure 4(b) is a low-magnification observation image of Figure 4(a), and the clear white line that was visible in Figure 14(b) has become fainter, indicating that the amorphous region has been reduced.

[0469] The volume percentage of the amorphous region in the superconducting film of Example 1 is calculated to be 0.27%. Even with this amount, a QFG is formed, but whether the quantum magnetic flux passes through the QFG or is trapped in the CARP depends on the superconducting potential.

[0470] Figure 27 is an explanatory diagram of the quantum magnetic flux state in Example 1. Figure 27 is a schematic diagram showing a cross-section of the superconducting film in Example 1. Figure 27 is a diagram showing the distribution of CARP and QFG in the superconducting film in Example 1.

[0471] Figure 27 shows a schematic cross-section of a superconductor in which the formation of a QFG is sufficiently suppressed. Because the QFG is small, the quantum magnetic flux does not enter the QFG due to the potential relationship, but enters the CARP instead.

[0472] Figure 28 is an explanatory diagram of the pinning effect in Example 1. Figure 28 is a schematic diagram showing the upper surface of the superconducting film in Example 1.

[0473] Figure 28 shows a situation where the quantum magnetic flux shifts to the left. Figure 28 is a schematic diagram of the case where a 5 nmΦ CARP is formed. The 5 nmΦ quantum magnetic flux is trapped by the CARP, which is an artificial pin of almost the same size (5 nmΦ). In this situation, the quantum magnetic flux is trapped and unable to move, thus improving the superconductivity in the magnetic field.

[0474] Next, let's explain whether the CARP and QFG with the structure shown in Figure 28 have a pinning effect at 77K. It has already been explained that the CARP does not have a pinning effect at 77K. The quantum magnetic flux of 50 nmΦ at 77K is shown in the upper left of Figure 28. The area of ​​the CARP is approximately 1 / 100 of the area of ​​the quantum magnetic flux at 77K. Therefore, if we compare the situation in which the CARP shown by the solid line is included inside the quantum magnetic flux at 77K with the potential in the quantum magnetic flux where the CARP is absent, shown by the dashed line, the former is 99% and the latter is 100%. Since the quantum magnetic flux moves by 5 nm and the change in potential is only this much, the CARP does not have a pinning effect at 77K.

[0475] The pinning effect of the QFG can be explained using the 50 nmΦ quantum magnetic flux in the center of Figure 28. Since the QFG is sufficiently narrow, for example, even if the quantum magnetic flux spans 40 nm, the width in this case is only a maximum of 3 nm, and the area is 210 nm. ２ This is because the area of ​​the CARP is 25 nm, which is 5 nm x 5 nm. ２This is 8.4 times greater. However, as mentioned above, the depth of the QFG is only 7 nm, which is 3.2% of the 220 nm thickness. This is less than half of the 8.0% of the CARP. When all of these are calculated, the superconducting potential of the QFG portion is equivalent to the superconducting potential of 3.4 CARPs contained inside. In other words, it is 96.6% of the potential.

[0476] A 5 nm shift in quantum magnetic flux results in a change in superconducting potential from 96.6% to 100.0%, indicating that the pinning force due to the QFG is almost nonexistent. When the QFG is narrowed, the pinning force does not act even at 77 K, which causes the denominators of α / β, α / γ, and α / δ to become small, and the numerical values ​​themselves to become large. The QFG is a structure that prevents the CARP from exerting its force, and α / β, α / γ, and α / δ are indicators of this. The larger the numerical value, the smaller the QFG amount and the easier it is for the CARP to exert its force.

[0477] The above data is shown in concrete numerical values ​​for α / β, α / γ, and α / δ in Table 1. As shown in the graph in Figure 26, the superconducting film of Example 1 has almost no pinning force at 77K. In other words, the formation of QFG is suppressed, and the characteristics tend to deteriorate at high magnetic fields. As a result, the values ​​of α / β, α / γ, and α / δ are 11.7, 103, and 2133, respectively.

[0478] In the comparative examples 1, 2A, and 2B shown so far, the α / β ratio was 2.9 to 3.5, the α / γ ratio was 5.3 to 7.0, and the α / δ ratio was 20 to 41. Compared to these, the α / β, α / γ, and α / δ values ​​of the superconducting film in Example 1 are remarkably large. Our group is currently the only one conducting research and development on CARP, and this is the first time we have achieved a structure that produces such large values ​​for all three of these parameters.

[0479] Among Comparative Examples 1, 2A, and 2B, Comparative Example 2A, which used fresh barium acetate, was the most effective in suppressing QFG. In Comparative Example 2A, even when all other chemicals were made from crystalline raw materials and their purity was increased to 99.4% or 99.8%, QFG was still formed, and the improvement in the α / β, α / γ, and α / δ values ​​was limited.

[0480] Figure 29 is an explanatory diagram of the pinning effect of the comparative example. Figure 29 is a schematic diagram showing the upper surface of the superconducting film of comparative example 2A.

[0481] Figure 29 is a schematic diagram illustrating that when many QFGs are formed, there is a pinning effect at 77K, but no pinning effect at 30K. In this diagram, the QFGs are approximately 7 nm wide. The fact that the effect disappears at 30K due to the large intrusion of quantum magnetic flux into the QFGs has already been explained above, so it will be omitted here.

[0482] On the other hand, at 77K, when a quantum magnetic flux of 50 nmΦ moves 7 nm, the area overlapping with the 50 nmΦ quantum magnetic flux in the QFG is thought to be approximately 10%. While this is not a large pinning force, it can be said to be a pinning force that has some influence. This is thought to have led to the improvement in characteristics at high magnetic fields at 77K, resulting in smaller values ​​for α / β, α / γ, and α / δ.

[0483] Determining the total amount of QFG is a very difficult task using Planview TEM or cross-sectional TEM observation, and it is almost impossible to determine it for the entire sample. However, this result shows that the α / β, α / γ, and α / δ values ​​reflect the amount of QFG formed, and thus serve as indicators that can reveal the internal structure.

[0484] Since the suppression of QFG formation is thought to be due to changing the barium acetate raw material to a crystalline type, in order to reconfirm this effect, we performed film deposition using a raw material that was a mixture of crystalline barium acetate and some conventional barium acetate, and investigated how QFG formation changed.

[0485] (Example 2) A coating solution for superconductors was prepared according to the flowchart shown in Figure 5. Praseodymium acetate with a purity of 99.4%, samarium acetate with a purity of 99.4%, yttrium acetate with a purity of 99.8%, copper acetate with a purity of 99.8%, and thulium acetate with a purity of 99.8% were used, calculated from the number of water crystals obtained by thermal analysis.

[0486] The 99.8% pure barium acetate monohydrate crystals used in Example 1 and the 97.0% pure barium acetate used in Comparative Example 2A were mixed in a 9:1 ratio, and this mixed barium acetate was used for solution synthesis. This allowed for an experiment to reconfirm that the raw material impurities are related to the amount of QFG formed. The average impurity content of the barium acetate was 0.48%, as shown in Table 2.

[0487] Praseodymium acetate, samarium acetate, thulium acetate, yttrium acetate, barium acetate, and copper acetate are mixed in a metal ion molar ratio of 2:2:4:92:200:300, dissolved in ion-exchanged water, and an equimolar amount of CF is reacted. ３ The mixture was mixed with COOH and stirred to obtain the solution ex-2-MOAc-Sol (aqueous acetate solution from Example 2).

[0488] The obtained solution, ex-2-MOAc-Sol, was placed in a round-bottom flask, and the reaction and purification were carried out under reduced pressure in a rotary evaporator for 12 hours to obtain a translucent blue substance, ex-2-blue-Mat-i (blue substance of Example 2: containing impurities).

[0489] The obtained substance ex-2-blue-Mat-i contains approximately 7 wt% water and acetic acid, which are reaction byproducts during solution synthesis. The translucent blue substance ex-2-blue-Mat-i was dissolved in 20 times its weight of anhydrous methanol to obtain a methanol solution ex-2-MeOH-Sol-i (methanol solution of Example 2: containing impurities of water and acetic acid).

[0490] The purification process shown in Figure 5h was performed. Further purification of the methanol solution ex-2-MeOH-Sol-i yielded a translucent blue substance, ex-2-blue-Mat (the blue substance from Example 2: free of impurities). This solution had significantly reduced impurities such as water and acetic acid.

[0491] The obtained translucent blue substance, ex-2-blue-Mat, was dissolved in a volumetric flask to a metal ion concentration of 1.50 mol / l to obtain the coating solution ex-2-coating-Sol (coating solution of Example 2).

[0492] Using the coating solution ex-2-coating-Sol and the spin coating method, a 10 × 28 × 0.50 mmt layer of LaAlO was produced with an acceleration of 10,000 rpm / s, a maximum rotation speed of 2,000 rpm, and a holding time of 60 s. ３ (100) A film was deposited on an oriented single crystal to obtain a translucent blue gel film ex-2-Gel (gel film of Example 2).

[0493] The obtained gel film, ex-2-Gel-film, was immediately placed in a furnace filled with drying gas. Organic matter was decomposed at X, 200-250°C, according to the profile shown in Figure 7, and the residue was removed at Y and Z, below 400°C, to obtain a translucent brown calcined film, ex-2-cal-film (calcined film of Example 2).

[0494] The calcined film ex-2-oxide-Cal-film was calcined at 750°C in a 250 ppm oxygen-mixed argon gas using the calcination profile shown in Figure 8, resulting in the oxide thin film ex-2-oxide-YBa ２ Cu ３ O ６．００ (YBa in Example 2) ２ Cu ３ O ６．００ ) was obtained.

[0495] Oxide thin film ex-2-oxide-YBa ２ Cu ３ O ６．００ Next, pure oxygen annealing is performed, and the oxygen count is processed to maximize the superconducting properties, resulting in the superconducting film ex-2-CARP-YBa ２ Cu ３ O ６．９３ (The superconducting film of Example 2) was obtained.

[0496] The superconducting film of Example 2 was measured using the 2θ / ω method of XRD measurement. The results were almost the same as those in Figure 15, indicating good YBa. ２ Cu ３ O ６．９３ It was found that only the (00n) peak was obtained. The figure is omitted.

[0497] In the XRD measurement of the superconducting film in Example 2, the different phase observed using the 2θ / ω method is Y, which is visible around 34 degrees. ２ O ３ And Ba can be seen at around 42 degrees. ２ CuO３ Both were small, indicating the formation of a well-oriented structure. This result was almost identical to that obtained for other superconducting films.

[0498] The ω-scan results using the (006) peak of the superconducting film in Example 2 were almost the same as those in Figure 16. It was found that there was almost no difference in the XRD measurements. Therefore, the figure is omitted.

[0499] The superconducting properties of the superconducting film in Example 2 were measured using the induction method in liquid nitrogen under its own magnetic field. In principle, the induction method requires the presence of a superconductor in a region of approximately 6 mm in diameter within the superconducting film to be evaluated. Therefore, only the properties of 4 to 6 points in the central region were obtained, but the highest value among these points was used to represent the characteristics of the superconducting film. The obtained superconducting property was 3.54 MA / cm². ２ (77K, 0T)

[0500] The superconducting film of Example 1 exhibits a characteristic of 4.04 MA / cm². ２ Although the characteristics are slightly lower than (77K, 0T), the characteristics of each sample can vary by about 5% during measurement, so the results are not considered to be significantly different. Considering the possibility that CARP is being formed, a bridge circuit was formed in the same manner as in Comparative Example 1, J ｃ -B-T measurement was performed.

[0501] Figure 30 shows the J of Example 2. ｃ This figure shows the measurement results of the B-T measurement. In Figure 30, the horizontal axis is the magnetic field in units of T, and the vertical axis is the logarithmic scale in J. ｃ These are the values. Measurements were taken at 20K and 77K, with a maximum magnetic field of 5T. At 30K, measurements were taken with a magnetic field applied up to a maximum of 15T.

[0502] We will first compare the data at 30K, where the quantum magnetic flux is 5 nmΦ. The characteristic at 30K and 5T is 1.82 MA / cm ２ (30K, 5T) ２ Cu ３ O ６．９３ This is significantly higher than the 1.09 for superconductors. However, this is compared to the result of 2.11 MA / cm shown in Figure 26 of Example 1. ２ It was also found that the performance was slightly lower compared to (30K, 5T).

[0503] Another characteristic of the 30K data is that the comparison target YBa is lower on the low magnetic field side. ２ Cu ３ O ６．９３ This characteristic of CARP was also seen in the results in Figure 28, which showed a greater degree of performance improvement than that of superconductors. If CARP is present and the QFG is formed to be sufficiently small, the performance improves as the quantum magnetic flux decreases at lower magnetic fields, and a similar improvement trend can be seen in the graph in Figure 30.

[0504] Looking at the 30K data for this sample, we can see that while the characteristics improve even at 15T, the improvement becomes more significant at 5T, and the graph shows further improvement at low magnetic fields of 3T and 1T. This can be considered one piece of evidence for the improvement in magnetic field characteristics due to the formation of CARP.

[0505] Another notable piece of data, similar to that in Figure 28, is the data for 77K. In Figure 30, the characteristics of the superconducting film of Comparative Example 0 are shown up to 3T. On the other hand, the characteristics of the superconducting film of Example 2 at 77K decrease with increasing magnetic field, and the graph is only shown up to 2.5T. Here too, the decrease in characteristics at a high magnetic field of 77K and the improvement in characteristics at a high magnetic field of 30K appear together, as explained in Figure 28.

[0506] The superconducting film in Example 2 also appears to have a reduced QFG, resulting in improved superconducting properties in a 30K magnetic field. If so, the α / β, α / γ, and α / δ values ​​shown in Table 1 should improve. This is confirmed in Table 1, including a comparison with the superconducting film in Example 1.

[0507] We compared the α / β, α / γ, and α / δ values ​​of the superconducting film in Example 1 and the superconducting film in Example 2. The α / β values ​​were 11.7 and 13.5 respectively, with the superconducting film in Example 2 being slightly higher. However, the α / γ values ​​were almost the same at 103 and 102, and the α / δ values ​​were 2,133 and 1,659, with the superconducting film in Example 1 being higher. There appears to be a difference due to the magnetic field, but the 5T characteristics are better in the superconducting film in Example 1, so this may be the reason for the higher α / δ, but the details are not yet known.

[0508] The superconducting film in Example 2 was prepared by intentionally adding 10% degraded barium acetate during sample preparation. On the other hand, the superconducting film in Example 1 was deposited without using any raw materials that cause amorphous formation. The superconducting film in Example 2 may have had its high magnetic field characteristics at 30K reduced due to the amount of barium acetate with degraded QFG.

[0509] The impurity content of the sample obtained this time was 0.6% praseodymium acetate, 0.6% samarium acetate, 0.2% thulium acetate, 0.2% yttrium acetate, 0.48% barium acetate, and 0.2% copper acetate. The total impurity content is 0.296%, as shown in Table 2. In Example 1, it was 0.203%, so it is thought that more QFGs were formed, resulting in lower performance at 30K. The data for 77K was the same at 5T.

[0510] In the comparative example, α / β, α / γ, and α / δ were all very low. This indicates that there is a certain correlation between the formation of QFG and the decrease in α / β, α / γ, and α / δ values, and that the purity of the barium acetate raw material is involved.

[0511] It appears clear from the results of Comparative Examples 1, 2A, 2B and Examples 1, 2 that QFG is formed from barium acetate degradation products, but QFG could also be derived from degradation products of other salts. Considering the growth mechanism of the pseudo-liquid phase network model, different phases should be pushed to the ends during the formation of unit cells, and these should accumulate at the ends of the unit cell aggregate to form QFG.

[0512] Therefore, in the following example, we decided to use a slightly degraded crystalline acetate from another source to investigate whether one of the origins of QFG is a degraded product of the raw material acetate. The raw material acetate contains only a small amount of CARP. Therefore, we decided to use a crystalline raw material of Y and Cu whose surface had discolored over time.

[0513] (Example 3) A coating solution for superconductors was prepared according to the flowchart shown in Figure 5. Praseodymium acetate with a purity of 99.4%, samarium acetate with a purity of 99.4%, barium acetate with a purity of 99.8%, and thulium acetate with a purity of 99.8% were used, calculated from the number of water molecules in the crystal structure obtained by thermal analysis.

[0514] Yttrium acetate and copper acetate were prepared by mixing crystalline raw materials with a purity of 99.8% with raw materials that had deteriorated during storage. Based on the mixing ratio and deterioration rate, the average purity of yttrium acetate is calculated to be 99.55%, and the average purity of copper acetate is calculated to be 99.51%. As a result, the total amount of impurities is calculated to be 0.386%, as shown in Table 2.

[0515] Praseodymium acetate, samarium acetate, thulium acetate, yttrium acetate, barium acetate, and copper acetate are mixed in a metal ion molar ratio of 2:2:4:92:200:300, dissolved in ion-exchanged water, and an equimolar amount of CF is reacted. ３ The mixture was mixed with COOH and stirred to obtain the solution ex-3-MOAc-Sol (aqueous acetate solution of Example 3).

[0516] The obtained solution, ex-3-MOAc-Sol, was placed in a round-bottom flask, and the reaction and purification were carried out under reduced pressure in a rotary evaporator for 12 hours to obtain a translucent blue substance, ex-3-blue-Mat-i (the blue substance of Example 3: containing impurities).

[0517] The obtained substance ex-3-blue-Mat-i contains approximately 7 wt% water and acetic acid, which are reaction byproducts during solution synthesis. The translucent blue substance ex-3-blue-Mat-i was dissolved in 20 times its weight of anhydrous methanol to obtain a methanol solution ex-3-MeOH-Sol-i (methanol solution of Example 3: containing impurities of water and acetic acid).

[0518] The purification process shown in Figure 5h was carried out. Further purification of the methanol solution ex-3-MeOH-Sol-i yielded a translucent blue substance, ex-3-blue-Mat (the blue substance from Example 3: free of impurities). This solution had significantly reduced impurities such as water and acetic acid.

[0519] The obtained translucent blue substance, ex-3-blue-Mat, was dissolved in a volumetric flask to a metal ion concentration of 1.50 mol / l to obtain the coating solution ex-3-coating-Sol (coating solution of Example 3).

[0520] Using the coating solution ex-3-coating-Sol and the spin coating method, a 10 × 28 × 0.50 mmt layer of LaAlO was produced with an acceleration of 10,000 rpm / s, a maximum rotation speed of 2,000 rpm, and a holding time of 60 s. ３ (100) A film was deposited on an oriented single crystal to obtain a translucent blue gel film ex-3-Gel (gel film of Example 3).

[0521] The obtained gel film, ex-3-Gel-film, was immediately placed in a furnace filled with drying gas. Organic matter was decomposed at X, 200-250°C, according to the profile shown in Figure 7, and the residue was removed at Y and Z, below 400°C, to obtain a translucent brown calcined film, ex-3-cal-film (calcined film of Example 3).

[0522] The calcined film ex-3-oxide-Cal-film was calcined at 750°C in a 250 ppm oxygen-mixed argon gas using the calcination profile shown in Figure 8, resulting in the oxide thin film ex-3-oxide-YBa ２ Cu ３ O ６．００ (YBa of Example 3) ２ Cu ３ O ６．００ ) was obtained.

[0523] Oxide thin film ex-3-oxide-YBa ２ Cu ３ O ６．００ Next, pure oxygen annealing is performed, and the oxygen count is processed to maximize the superconducting properties, resulting in the superconducting film ex-3-CARP-YBa ２ Cu ３ O ６．９３ (The superconducting film of Example 3) was obtained.

[0524] The superconducting films of Example 3 were measured using the 2θ / ω method of XRD measurement. The results were almost the same as those in Figure 15, indicating good YBa. ２ Cu ３ O ６．９３It was found that only the (00n) peak was obtained.

[0525] The XRD measurement of the superconducting film in Example 3 using the 2θ / ω method shows a different phase, with a Y-shaped phase visible around 34 degrees. ２ O ３ And Ba can be seen at around 42 degrees. ２ CuO ３ Both were small, indicating the formation of well-oriented tissue.

[0526] The ω-scan results using the (006) peak of the superconducting film in Example 3 were almost the same as those in Figure 16. It was found that there was almost no difference in the XRD measurements.

[0527] The superconducting properties of the superconducting film in Example 3 were measured using the induction method in liquid nitrogen under its own magnetic field. In principle, the induction method requires the presence of a superconductor in a region of approximately 6 mm in diameter within the superconducting film to be evaluated. Therefore, only the properties of 4 to 6 points in the central region were obtained, but the highest value among these points was used to represent the characteristics of the superconducting film. The obtained superconducting property was 3.62 MA / cm². ２ (77K, 0T)

[0528] The properties of the superconducting film in Example 3 are 3.62 MA / cm². ２ (77K, 0T), which is not significantly different from Example 1 and Example 2. At this point, we do not consider this difference to be significant. We consider that CARP may also be formed in this sample, and we formed a bridge circuit in the same way as in Example 1, J ｃ -B-T measurement was performed.

[0529] Figure 31 shows the J of Example 3. ｃ This figure shows the measurement results of the B-T measurement. In Figure 31, the horizontal axis is the magnetic field in units of T, and the vertical axis is the logarithmic scale of J. ｃ These are the values. Measurements were taken at 20K and 77K, with a maximum magnetic field of 5T. At 30K, measurements were taken with a magnetic field applied up to a maximum of 15T.

[0530] We will first compare the data at 30K, where the quantum magnetic flux is 5 nmΦ. The characteristic at 30K and 5T is 1.69 MA / cm ２(30K, 5T) is significantly higher than the 1.10 of the superconducting thin film in Comparative Example 0. However, the results for the superconducting film in Example 1 and the superconducting film in Example 2 were 2.11 MA / cm², respectively. ２ (30K, 5T), and 1.82 MA / cm ２ (30K, 5T) Therefore, it was also found that CARP showed the smallest improvement in characteristics at 30K, 5T.

[0531] The 30K data shows a characteristic improvement in performance at low magnetic fields, and while it tends to show improvement at lower magnetic fields than the superconducting thin film of Comparative Example 0, the degree of performance improvement is smaller, as can be seen from the figure. Furthermore, the phenomenon of a significant drop in performance at a high magnetic field of 77K appears to be smaller compared to the superconducting films of Example 1 and Example 2.

[0532] We investigated whether the above 77K results could be distinguished by α / β, α / γ, and α / δ. The results are shown in Table 1. For the superconducting films of Example 1, Example 2, and Example 3, the α / β values ​​were 11.7, 13.5, and 7.8 respectively, the α / γ values ​​were 103, 102, and 31, and the α / δ values ​​were 2,133, 1,659, and 702. The data for Comparative Example 2A were 3.5, 7.0, and 41 for α / β, α / γ, and α / δ respectively, so it can be seen that significantly larger values ​​were obtained.

[0533] The superconducting film of Example 3 has the smallest α / β, α / γ, and α / δ values ​​among Examples 1 to 3. Considering that the calculated total impurity amounts are 0.203%, 0.296%, and 0.386%, respectively, it is clear that the magnitude of these values ​​indicates a reduction in impurity levels and suppression of QFG.

[0534] Although the superconducting film of Example 3 was observed using Planview TEM, it showed a structure similar to Figures 4(a) and 4(b), with few amorphous regions, and no clear differences were immediately apparent. Even if impurities formed QFG, there was no difference from the sample shown in the comparative example, so it is thought that it could not be distinguished at a glance. The three values ​​α / β, α / γ, and α / δ seem to be useful as they represent the overall average.

[0535] Similarly, cross-sectional TEM observation was also performed, but here too, only a highly oriented structure was observed, and no difference from the cross-section of Example 1 could be found. Regarding CARP formation, QFG, which reduces the effect of CARP, cannot be suppressed unless the amount of impurities is below 1%. However, in the state where the effect of CARP is exerted, the amount of QFG is quite small, and it is considered difficult to distinguish it in Planview TEM observation images or cross-sectional TEM observation images. For this reason, this observation will be omitted from now on.

[0536] The results from Example 3 suggest that QFG, which inhibits the improvement of CARP properties, is related not only to barium acetate but also to the degradation products of yttrium acetate and copper acetate. Although the amount is small and therefore unlikely to have much effect, the same is likely true for praseodymium acetate, samarium acetate, and thulium acetate.

[0537] The minimum total impurity content when barium acetate hydrate is not used is calculated to be 1.133%. In the following examples, we decided to investigate whether the superconductivity improvement effect of CARP is observed in samples with an impurity content of around 1.00%, which cannot be achieved without using barium acetate hydrate.

[0538] (Examples 4A, 4B) A coating solution for superconductors was prepared according to the flowchart shown in Figure 5. Praseodymium acetate with a purity of 99.4%, samarium acetate with a purity of 99.4%, and thulium acetate with a purity of 99.8% were used, calculated from the number of water crystals obtained by thermal analysis.

[0539] The mixed salts used in Example 3 were used for yttrium acetate and copper acetate. The average purity of yttrium acetate is estimated to be 99.55%, and the average purity of copper acetate is estimated to be 99.51%. For barium acetate, crystalline barium acetate monohydrate and the anhydrous barium acetate from the comparative example were mixed to obtain ex-4-BaOAc-A (mixed barium acetate from Example 4A) with an estimated purity of 98.99% and ex-4-BaOAc-B (mixed barium acetate from Example 4B) with an estimated purity of 97.84%. The impurities of all elements were calculated to be 0.656% and 1.039%, respectively, as shown in Table 1.

[0540] Praseodymium acetate, samarium acetate, thulium acetate, yttrium acetate, barium acetate, and copper acetate are mixed in a metal ion molar ratio of 2:2:4:92:200:300, dissolved in ion-exchanged water, and an equimolar amount of CF is reacted. ３ COOH was mixed and stirred to obtain ex-4-MOAc-Sol-A (aqueous acetate solution of Example 4A) using ex-4-BaOAc-A and ex-4-MOAc-Sol-B (aqueous acetate solution of Example 4B) using ex-4-BaOAc-B.

[0541] The obtained solutions ex-4-MOAc-Sol-A and ex-4-MOAc-Sol-B were placed in a round-bottom flask, and the reaction and purification were carried out under reduced pressure in a rotary evaporator for 12 hours to obtain the translucent blue substances ex-4-blue-Mat-A-i (blue substance of Example 4A: containing impurities) and ex-4-blue-Mat-B-i (blue substance of Example 4B: containing impurities), respectively.

[0542] The obtained substances ex-4-blue-Mat-A-i and ex-4-blue-Mat-B-i each contain approximately 7 wt% water and acetic acid, which are reaction byproducts during solution synthesis. The translucent blue substances ex-4-blue-Mat-A-i and ex-4-blue-Mat-B-i were each dissolved in 20 times their weight in anhydrous methanol to obtain methanol solutions ex-4-MeOH-Sol-A-i (methanol solution of Example 4A: containing impurities of water and acetic acid) and ex-4-MeOH-Sol-B-i (methanol solution of Example 4B: containing impurities of water and acetic acid).

[0543] The purification process shown in Figure 5h was performed. Further purification of the methanol solutions ex-4-MeOH-Sol-A-i and ex-4-MeOH-Sol-B-i yielded translucent blue substances ex-4-blue-Mat-A (the blue substance of Example 4A) and ex-4-blue-Mat-B (the blue substance of Example 4B), respectively. These solutions had significantly reduced impurities such as water and acetic acid.

[0544] The obtained translucent blue substances, ex-4-blue-Mat-A and ex-4-blue-Mat-B, were dissolved in a volumetric flask to a metal ion concentration of 1.50 mol / l to obtain coating solutions ex-4-coating-Sol-A (coating solution of Example 4A) and ex-4-coating-Sol-B (coating solution of Example 4B), respectively.

[0545] Using coating solutions ex-4-coating-Sol-A and ex-4-coating-Sol-B, a spin coating method was used with an acceleration of 10,000 rpm / s, a maximum rotation speed of 2,000 rpm, and a holding time of 60 s to produce 10 × 28 × 0.50 mmt of LaAlO₂. ３ (100) A film was formed on an oriented single crystal to obtain translucent blue gel films ex-4-Gel-film-A (gel film of Example 4A) and ex-4-Gel-film-B (gel film of Example 4B), respectively.

[0546] The obtained gel films ex-4-Gel-film-A and ex-4-Gel-film-B were immediately placed in a furnace filled with drying gas, and organic matter was decomposed at X at 200-250°C according to the profile shown in Figure 7. The residue was then removed at Y and Z at temperatures below 400°C to obtain translucent brown calcined films ex-4-cal-film-A (calcined film of Example 4A) and ex-4-cal-film-B (calcined film of Example 4B).

[0547] The calcined films ex-4-cal-film-A and ex-4-cal-film-B were calcined at 750°C in a 250 ppm oxygen-mixed argon gas using the calcination profile shown in Figure 8, resulting in the oxide thin film ex-4-oxide-YBa. ２ Cu ３ O ６．００ -A (YBa in Example 4A) ２ Cu ３ O ６．００ ), and ex-4-oxide-YBa ２ Cu ３ O ６．００ -B (YBa of Example 4B) ２ Cu ３ O ６．００ They obtained the following results.

[0548] Oxide thin film ex-4-oxide-YBa ２ Cu ３ O ６．００ -A, and ex-4-oxide-YBa ２ Cu ３ O ６．００ -B then undergoes pure oxygen annealing, and the oxygen count is processed to maximize the superconducting properties, resulting in the superconducting film ex-4-CARP-YBa ２ Cu ３ O ６．９３ -A (superconducting film of Example 4A), and ex-4-CARP-YBa ２ Cu ３ O ６．９３ -B (the superconducting film of Example 4B) was obtained.

[0549] The superconducting films of Example 4A and Example 4B were measured using the 2θ / ω method of XRD measurement. The results were almost the same as those shown in Figure 15, indicating good YBa. ２ Cu ３ O ６．９３ It was found that only the (00n) peak was obtained.

[0550] The different phases observed in the 2θ / ω method of XRD measurements of the superconducting film in Example 4A and the superconducting film in Example 4B are Y, which is visible around 34 degrees. ２ O ３ And Ba can be seen at around 42 degrees. ２ CuO ３ Both were small, indicating the formation of well-oriented tissue.

[0551] The ω-scan results using the (006) peak of the superconducting film in Example 4A and the superconducting film in Example 4B were almost the same as those in Figure 16. It was found that there was almost no difference in the XRD measurements.

[0552] The superconducting properties of the superconducting films of Example 4A and Example 4B were measured in liquid nitrogen under a self-magnetic field using the induction method. In principle, the induction method requires the presence of a superconductor in a region of approximately 6 mm in diameter within the superconducting film to be evaluated. Therefore, only the properties of 4 to 6 points in the central region were obtained, but the highest value among these points was used as the characteristic of the superconducting film. The obtained superconducting properties were 3.77 MA / cm². ２(77K, 0T) and 3.89 MA / cm ２ (77K, 0T)

[0553] J obtained in Examples 1-3 ｃ The above characteristics appear to be almost identical to those of the value (77K, 0T). Considering the good XRD measurement results and other factors, it is thought that CARP may also be formed in this sample, and a bridge circuit was formed in the same manner as in Example 1, J ｃ -B-T measurement was performed.

[0554] The superconducting film of Example 4A and the superconducting film of Example 4B ｃ - The B-T measurement results are summarized in Table 1. J ｃ (30K, 5T) are 1.56 MA / cm, respectively. ２ (30K, 5T) and 1.39 MA / cm ２ (30K, 5T) In particular, the superconducting film of Example 4B showed that while the CARP effect was present, the effect was considered to be small. In the case where the total impurity amount is calculated to be 1.133%, which is the minimum value when barium acetate hydrate is not used, the result was 1.28 MA / cm ２ (30K, 5T) Therefore, due to the effect of the structure according to the present invention, it is 1.30 MA / cm ２ It is expected that characteristics of (30K, 5T) or higher will be achieved.

[0555] Table 1 shows the α / β, α / γ, and α / δ values, which are thought to quantitatively evaluate the effect of CARP. The values ​​for the superconducting film of Example 4A and Example 4B were 5.3, 16, and 175, respectively, and 4.1, 10.1, and 68. Both samples showed results intermediate between the superconducting film of Comparative Example 2A and the superconducting film of Example 3. These values ​​increase when the amount of QFG is suppressed, and the decomposition products of acetate that cause this are related to the amount of QFG. The results for the superconducting film of Example 4B are thought to be close to the minimum α / β, α / γ, and α / δ values ​​in the present invention.

[0556] Note that Planview TEM observation and cross-sectional TEM observation were not performed on the superconducting films of Example 4A and Example 4B. This is because, based on the results obtained so far, it is easy to imagine that the results would be intermediate.

[0557] Whether CARP is effective or not seems to depend on whether it can prevent the formation of QFGs near the film surface. The indicators for this are α / β, α / γ, and α / δ, and it is thought that the larger these values ​​are, the more QFG formation is suppressed and the more likely the effect of CARP is to be observed. For this reason, we decided to create a graph of the α / β, α / γ, and α / δ values ​​obtained so far, using the amount of impurities in the total amount of acetic acid.

[0558] Figures 32, 33, 34, and 35 are explanatory diagrams illustrating the operation and effects of the examples. In Figures 32, 33, 34, and 35, the horizontal axis represents the total amount of impurities (%) in total acetic acid, and the vertical axis represents the values ​​of α / β, α / γ, or α / δ. Hereinafter, the values ​​of α / β, α / γ, and α / δ will be referred to as the QFG index.

[0559] Figure 32 shows the logarithmic values ​​of α / β, α / γ, and α / δ on the vertical axis. As is clear from Figure 32, the QFG index increases as the total amount of impurities decreases. In other words, the QFG index improves as the total amount of impurities decreases.

[0560] Figure 33 shows α / β on the vertical axis. Data with a total impurity amount greater than 1.10% are from the comparative example. The superconducting film of the comparative example exhibits good superconducting properties and XRD measurement results, but the presence of QFG on the surface and the structure suggest that even if CARP is formed internally, its effect cannot be realized.

[0561] The data for Example 4B, which is thought to represent the minimum amount of impurities at which the CARP according to the present invention can exert its effect, shows a total impurity amount of 1.039%. The data for Example 4A shows a total impurity amount of 0.656%.

[0562] The data for the examples shows a total impurity amount of 1.039% or less. In the examples, α / β > 4.0 was achieved.

[0563] Figure 34 shows α / γ on the vertical axis. Data where the total impurity amount is 1.039% or less are from the examples. In the examples, α / γ > 10 was achieved.

[0564] Figure 35 shows α / δ on the vertical axis. Data with a total impurity amount of 1.039% or less are the data for the examples. The δ data is the 5T data, and Jｃ As can be seen from the B-T graph, the comparative example samples, in which QFG is suppressed, tend to have extremely low performance. In the example, α / δ > 80 is achieved.

[0565] As can be seen from the above examples, the amount of QFG can only be evaluated at specific points through direct observation. However, by using α / β, α / γ, and α / δ values, it is possible to determine to what extent QFG formation is suppressed and how easily the effect of CARP is exerted. The structure of the present invention is one in which QFG containing CARP is suppressed, and it has been found that its success or failure can be determined by the α / β, α / γ, and α / δ values.

[0566] Among acetates, praseodymium acetate and samarium acetate are prone to degradation. Their valency changes, causing internal decay, and their quality deteriorates over time. Thermal analysis of the water content also shows an increase in indicators of degradation in these light rare-earth acetates. However, the impact of decomposition is likely small due to the small quantity involved.

[0567] In the following example, degraded praseodymium acetate and samarium acetate were used to investigate whether the α / β, α / γ, and α / δ values ​​changed. Furthermore, the effectiveness of CARP was investigated.

[0568] (Example 5) A coating solution was prepared according to the flowchart shown in Figure 5. The degradation of crystalline acetates of praseodymium acetate and samarium acetate was investigated to see if they had any effect. Yttrium acetate with a purity of 99.8%, barium acetate with a purity of 99.8%, copper acetate with a purity of 99.8%, and thulium acetate with a purity of 99.8% were used, calculated from the number of water molecules in crystallization by thermal analysis.

[0569] Crystalline raw materials with a purity of 97.6% for praseodymium acetate and 97.8% for samarium acetate were used. Ex-5-BaOAc (mixed acetate of Example 5) with an estimated purity of 99.79% was obtained. The total amount of impurities was calculated to be 0.21%.

[0570] Praseodymium acetate, samarium acetate, thulium acetate, yttrium acetate, barium acetate, and copper acetate are mixed in a metal ion molar ratio of 2:2:4:92:200:300, dissolved in ion-exchanged water, and an equimolar amount of CF is reacted.３ COOH was mixed and stirred to obtain the solution ex-5-MOAc-Sol (aqueous acetate solution of Example 5) using ex-5-BaOAc.

[0571] The obtained solution, ex-5-MOAc-Sol, was placed in a round-bottom flask, and the reaction and purification were carried out under reduced pressure in a rotary evaporator for 12 hours to obtain a translucent blue substance, ex-5-blue-Mat-i (the blue substance in Example 5: containing impurities).

[0572] The obtained substance ex-5-blue-Mat-i contains approximately 7 wt% water and acetic acid, which are reaction byproducts during solution synthesis. The translucent blue substance ex-5-blue-Mat-i was dissolved in 20 times its weight of anhydrous methanol to obtain a methanol solution ex-5-MeOH-Sol-i (methanol solution obtained in Example 5: containing impurities of water and acetic acid).

[0573] The purification process shown in Figure 5h was carried out. Further purification of the methanol solution ex-5-MeOH-Sol-i yielded a translucent blue substance, ex-5-blue-Mat (the blue substance from Example 5: free of impurities). This solution had significantly reduced impurities such as water and acetic acid.

[0574] The obtained translucent blue substance, ex-5-blue-Mat, was dissolved in a volumetric flask to a metal ion concentration of 1.50 mol / l to obtain the coating solution ex-5-coating-Sol (coating solution of Example 5).

[0575] Using the coating solution ex-5-coating-Sol and the spin coating method, a 10 × 28 × 0.50 mmt layer of LaAlO was produced with an acceleration of 10,000 rpm / s, a maximum rotation speed of 2,000 rpm, and a holding time of 60 s. ３ (100) A film was deposited on an oriented single crystal to obtain a translucent blue gel film ex-5-Gel-film (gel film of Example 5).

[0576] The obtained gel film, ex-5-Gel-film, was immediately placed in a furnace filled with drying gas. Organic matter was decomposed at X, 200-250°C, according to the profile shown in Figure 7, and the residue was removed at Y and Z, below 400°C, to obtain a translucent brown calcined film, ex-5-cal-film (calcined film of Example 5).

[0577] The calcined film ex-5-cal-film was calcined at 750°C in a 250 ppm oxygen-mixed argon gas using the calcination profile shown in Figure 8, resulting in the oxide thin film ex-5-oxide-YBa. ２ Cu ３ O ６．００ (YBa in Example 5) ２ Cu ３ O ６．００ ) was obtained.

[0578] Oxide thin film ex-5-oxide-YBa ２ Cu ３ O ６．００ Next, pure oxygen annealing is performed, and the oxygen count is processed to maximize the superconducting properties, resulting in the superconducting film ex-5-CARP-YBa ２ Cu ３ O ６．９３ (The superconducting film of Example 5) was obtained.

[0579] The superconducting films of Example 5 were measured using the 2θ / ω method of XRD measurement. The results were almost the same as those in Figure 15, indicating good YBa. ２ Cu ３ O ６．９３ It was found that only the (00n) peak was obtained.

[0580] In the XRD measurement of the superconducting film in Example 5, the different phase observed using the 2θ / ω method is Y, which is visible around 34 degrees. ２ O ３ And Ba can be seen at around 42 degrees. ２ CuO ３ Both were small, indicating the formation of well-oriented tissue.

[0581] The ω-scan results using the (006) peak of the superconducting film in Example 5 were almost the same as those in Figure 16. It was found that there was almost no difference in the XRD measurements.

[0582] The superconducting film of Example 5 was measured for superconducting properties by the induction method in liquid nitrogen under self-magnetic field. In principle, for the evaluation of superconducting properties by the induction method, the properties cannot be evaluated unless a superconductor exists in a region with a diameter of about 6 mm in the target superconducting film. Therefore, the properties of only 4 to 6 points in the central part are obtained, and the highest value is regarded as the property of the superconducting film. The obtained superconducting property was 3.88 MA / cm ２ (77 K, 0 T).

[0583] Comparing with the J ｃ values (77 K, 0 T) obtained in Examples 1 to 4, the above properties seem to be almost the same. Considering that this sample may also form CARP including good XRD measurement results, a bridge circuit was formed in the same manner as in Example 1, and J ｃ - B - T measurement was carried out.

[0584] The J ｃ - B - T measurement results of the superconducting film of Example 5 are shown in Table 1. J ｃ (30 K, 5 T) was 2.00 MA / cm ２ (30 K, 5 T). The total impurity amount was calculated to be 0.214%, and it is considered to be a superconducting film close to that of Example 2.

[0585] The α / β, α / γ, α / δ values, which are considered to quantitatively evaluate the effect of CARP, are shown in Table 1. For the superconducting film ex - 5 - CARP - YBa ２ Cu ３ O ６．９３ the numerical values were 13.2, 98, and 1,597 in order. This result is close to that of the superconducting film of Example 2.

[0586] The difference between the raw material of the superconducting film of Example 5 and the raw material of the superconducting film of Example 2 is praseodymium acetate and samarium acetate, and the impurity amounts are 1.80% and 1.60% respectively. However, praseodymium acetate and samarium acetate together only substitute 4% of yttrium acetate, and yttrium acetate itself is only for 1 / 6 site of all metal elements, so the absolute amount is small. Therefore, the further formation of the amorphous region becomes small, and it seems to have become the same α / β, α / γ, α / δ.

[0587] Furthermore, the properties of CARP do not appear to differ significantly. If we consider how much CARP decreased due to the presence of degraded products in praseodymium acetate and samarium acetate, the estimated average reduction is calculated to be 2.30%. If this is the average, it means that the amount of CARP decreased from 99.4% to 97.7%.

[0588] If the amount of CARP decreased by 2%, the effect should also be 2%, but it is possible that this was masked by the error and did not show up in this case. The difference was that small. What we can conclude from this result is that what inhibits the effect of CARP is the degradation product of acetate, and it is thought that the degradation product of acetate forms QFG. Therefore, if the absolute amount is small, the effect is unlikely to be noticeable, and even if it is an element that makes up CARP, if the difference is small, the effect will be small as well.

[0589] It is thought that the formation of CARP is determined by small lattice mismatches. If so, a change should be observed when the CA of the CARP is changed to Er, which has a small lattice mismatch. This change would be that the lattice mismatch becomes smaller, improving the generation frequency of each component, leading to the formation of many smaller CARPs and a greater improvement in magnetic field characteristics.

[0590] However, negative effects can also be anticipated. One risk is that the lattice mismatch becomes too small, making it impossible to construct the CARP itself. In that case, the superconducting properties in a magnetic field would deteriorate drastically, which should make it detectable.

[0591] (Example 6) A coating solution was prepared according to the flowchart shown in Figure 5. Here, a CARP film consisting of praseodymium, samarium, and erbium was formed, and it was decided to investigate whether there was any difference compared to the case of praseodymium, samarium, and thulium.

[0592] Crystalline acetates containing hydration water were used as raw materials. Purity was calculated from the number of water molecules in crystallization obtained by thermal analysis. We prepared praseodymium acetate (99.4% purity), samarium acetate (99.4% purity), erbium acetate (99.8% purity), yttrium acetate (99.8% purity), barium acetate (99.8% purity), and copper acetate (99.8% purity). The total impurity content was calculated to be 0.203%.

[0593] Praseodymium acetate, samarium acetate, erbium acetate, yttrium acetate, barium acetate, and copper acetate are mixed in a metal ion molar ratio of 2:2:4:92:200:300, dissolved in ion-exchanged water, and an equimolar amount of CF is reacted. ３ COOH was mixed and stirred to obtain the solution ex-6-MOAc-Sol (aqueous acetate solution of Example 6) using ex-6-BaOAc.

[0594] The obtained solution, ex-6-MOAc-Sol, was placed in a round-bottom flask, and the reaction and purification were carried out under reduced pressure in a rotary evaporator for 12 hours to obtain a translucent blue substance, ex-6-blue-Mat-i (blue substance of Example 6: containing impurities).

[0595] The obtained substance ex-6-blue-Mat-i contains approximately 7 wt% water and acetic acid, which are reaction byproducts during solution synthesis. The translucent blue substance ex-6-blue-Mat-i was dissolved in 20 times its weight of anhydrous methanol to obtain methanol solution ex-6-MeOH-Sol-i (methanol solution A of Example 6: containing impurities of water and acetic acid).

[0596] The purification process shown in Figure 5h was carried out. Further purification of the methanol solution ex-6-MeOH-Sol-i yielded a translucent blue substance, ex-6-blue-Mat (the blue substance from Example 6: free of impurities). This solution had significantly reduced impurities such as water and acetic acid.

[0597] The obtained translucent blue substance, ex-6-blue-Mat, was dissolved in a volumetric flask to a metal ion concentration of 1.50 mol / l to obtain the coating solution ex-6-coating-Sol (coating solution of Example 6).

[0598] Using the coating solution ex-6-coating-Sol and the spin coating method, a 10 × 28 × 0.50 mmt layer of LaAlO was produced with an acceleration of 10,000 rpm / s, a maximum rotation speed of 2,000 rpm, and a holding time of 60 s. ３ (100) A film was deposited on an oriented single crystal to obtain a translucent blue gel film ex-6-Gel-film (gel film of Example 6).

[0599] The obtained gel film, ex-6-Gel-film, was immediately placed in a furnace filled with drying gas. Organic matter was decomposed at X, 200-250°C, according to the profile shown in Figure 7, and the residue was removed at Y and Z, below 400°C, to obtain a translucent brown calcined film, ex-6-cal-film (calcined film of Example 6).

[0600] The calcined film ex-6-cal-film was calcined at 750°C in a 250 ppm oxygen-mixed argon gas using the calcination profile shown in Figure 8, resulting in the oxide thin film ex-6-oxide-YBa. ２ Cu ３ O ６．００ (YBa of Example 6) ２ Cu ３ O ６．００ ) was obtained.

[0601] Oxide thin film ex-6-oxide-YBa ２ Cu ３ O ６．００ Next, pure oxygen annealing is performed, and the oxygen count is processed to maximize the superconducting properties, resulting in the superconducting film ex-6-CARP-YBa ２ Cu ３ O ６．９３ (The superconducting film of Example 6) was obtained.

[0602] The superconducting films of Example 6 were measured using the 2θ / ω method of XRD measurement. The results were almost the same as those in Figure 15, indicating good YBa. ２ Cu ３ O ６．９３ It was found that only the (00n) peak was obtained.

[0603] The XRD measurement of the superconducting film in Example 6 shows a different phase in the 2θ / ω method, with a Y-shaped phase visible around 34 degrees. ２ O ３ And Ba can be seen at around 42 degrees. ２ CuO ３ Both were small, indicating the formation of well-oriented tissue.

[0604] The ω-scan results using the (006) peak of the superconducting film in Example 6 were almost the same as those in Figure 14. It was found that there was almost no difference in the XRD measurements.

[0605] The superconducting properties of the superconducting film in Example 6 were measured using the induction method in liquid nitrogen under its own magnetic field. In principle, the induction method requires the presence of a superconductor in a region of approximately 6 mm in diameter within the superconducting film to be evaluated. Therefore, only the properties of 4 to 6 points in the central region were obtained, but the highest value among these points was used to represent the characteristics of the superconducting film. The obtained superconducting property was 3.26 MA / cm². ２ (77K, 0T)

[0606] J obtained in Examples 1 to 5 ｃ Compared to the value (77K, 0T), the characteristics of Example 6 are slightly lower. However, Examples 1-5 are CARP with Tm, while Example 6 is a CARP with Er. This difference may be the reason, but the value is not extremely low. Considering the good XRD measurement results and other factors, it is thought that this sample may also be forming CARP, and a bridge circuit was formed in the same way as in Example 1, J ｃ -B-T measurement was performed.

[0607] Figure 36 shows the J of Example 6. ｃ This figure shows the measurement results of the B-T measurement. In Figure 36, the horizontal axis is the magnetic field in units of T, and the vertical axis is the logarithmic J. ｃ This is the value. Measurements were taken at 20K and 77K, with a maximum measurement of 5T. At 30K, measurements were taken with a magnetic field applied up to a maximum of 15T. Example 6 J ｃ The B-T measurement results are also shown in Table 1.

[0608] J ｃ (30K, 5T) is 2.56 MA / cm ２ The values ​​were (30K, 5T). The total impurity content was calculated to be 0.203%, which is considered to be a superconducting film similar to that of Example 1. The characteristics are a step above those of the other examples, and it is presumed that there is a difference in Tm and Er.

[0609] J of the superconducting film in Example 6 ｃThe value at (30K, 5T) is very high compared to the characteristics of other embodiments. The trend in Figure 36 is not significantly different from that of other embodiments. However, what is concerning is the improvement in characteristics at low magnetic fields. For example, regarding the improvement in characteristics at 30K, the characteristics improve as the magnetic field gets lower, but below 1T, the characteristics seem to plateau rather than improve significantly.

[0610] However, this can also be seen as a result that correctly illustrates the physical phenomena caused by artificial pins. As explained earlier, artificial pins only serve to mitigate the degradation of properties caused by quantum magnetic flux. Considering that, J ｃ (20K, 0T) is 40 MA / cm ２ (20K, 0T) is the upper limit, and characteristics exceeding it are impossible. Unless there is a phenomenon where quantum magnetic flux exists and the critical current density of the original superconductor increases, but such a phenomenon does not exist. Even in the case of matching magnetic fields, there are no reliable records of exceeding the original superconducting characteristics.

[0611] In that case, J at 20K ｃ - The B-T characteristic is 40 MA / cm as the magnetic field approaches zero. ２ As we approach (20K, 0T), the improvement in characteristics should plateau. No matter how many artificial pins are present, the current should not exceed the original superconducting characteristics. This trend can be seen in Figure 36, as the characteristics at low magnetic fields of 20K and 30K have plateaued.

[0612] Table 1 shows the α / β, α / γ, and α / δ values, which appear to quantitatively evaluate the effect of CARP on the superconducting film of Example 6. The values ​​are 32.0, 618, and 2,637, respectively, which are exceptionally high. This result suggests that the properties change significantly when the elemental species of CARP are changed. Among these, only the α / δ value shows a close value, which is because J ｃ The value (77K, 5T) is too small, which may be why the measurement is not accurate.

[0613] PrBa ２ Cu ３ O ６．９３ SmBa ２ Cu ３ O６．９３ , ErBa ２ Cu ３ O ６．９３ The CARP (Sm-Er-CARP) formed by is, PrBa ２ Cu ３ O ６．９３ , SmBa ２ Cu ３ O ６．９３ , TmBa ２ Cu ３ O ６．９３ formed by is smaller than the CARP (Sm-Tm-CARP). Inside YBa ２ Cu ３ O ６．９３ it may be possible to form it smaller. This is due to the lattice mismatch shown in Table 3.

[0614] Table 3 is the data of the a-axis length read from the paper. Regarding YBa ２ Cu ３ O ６．９３ as a reference, the lattice mismatch of TmBa ２ Cu ３ O ６．９３ is -0.31%, and it can be seen that the lattice mismatch of ErBa ２ Cu ３ O ６．９３ is -0.18%. That is, the lattice mismatch of ErBa ２ Cu ３ O ６．９３ is smaller, and the nucleation frequency for the growth of YBa ２ Cu ３ O ６．９３ is greater than that of TmBa ２ Cu ３ O ６．９３ .

[0615] [[ID=​​

[0617] While it was found that CARP (Sm-Er-CARP) improves magnetic field properties, it is necessary to investigate whether CARP made from other elements also forms QFGs when there are many heterogeneous phases, thereby eliminating the effect of CARP. Since QFGs are amorphous regions formed by the aggregation of impurities, it is likely that the effect of CARP will be lost, but this was investigated in Comparative Example 3.

[0618] (Comparative Example 3) A coating solution was prepared according to the flowchart shown in Figure 5. Here, we investigated whether a CARP composed of praseodymium, samarium, and erbium would function as a CARP when a large amount of decomposition products were present in barium acetate, forming a QFG.

[0619] Crystalline acetates containing water of hydration were prepared as raw materials. Purity was calculated from the number of water molecules in crystallization obtained by thermal analysis. Praseodymium acetate with a purity of 99.4%, samarium acetate with a purity of 99.4%, erbium acetate with a purity of 99.8%, yttrium acetate with a purity of 99.8%, and copper acetate with a purity of 99.8% were prepared. For barium acetate, the barium acetate with an impurity amount of 4.5% used in Comparative Example 1 was used. The total amount of impurities was calculated to be 1.636%.

[0620] Praseodymium acetate, samarium acetate, erbium acetate, yttrium acetate, barium acetate, and copper acetate are mixed in a metal ion molar ratio of 2:2:4:92:200:300, dissolved in ion-exchanged water, and an equimolar amount of CF is reacted. ３ COOH was mixed and stirred to obtain the solution ex-7-MOAc-Sol (aqueous acetate solution of Comparative Example 3) using ex-7-BaOAc.

[0621] The obtained solution, ex-7-MOAc-Sol, was placed in a round-bottom flask, and the reaction and purification were carried out under reduced pressure in a rotary evaporator for 12 hours to obtain a translucent blue substance, ex-7-blue-Mat-i (blue substance of Comparative Example 3: containing impurities).

[0622] The obtained substance ex-7-blue-Mat-i contains approximately 7 wt% water and acetic acid, which are reaction byproducts during solution synthesis. The translucent blue substance ex-7-blue-Mat-i was dissolved in 20 times its weight of anhydrous methanol to obtain a methanol solution ex-7-MeOH-Sol-i (methanol solution of Comparative Example 3: containing impurities of water and acetic acid).

[0623] The purification process shown in Figure 5h was performed. Further purification of the methanol solution ex-7-MeOH-Sol-i yielded a translucent blue substance, ex-7-blue-Mat (the blue substance in Comparative Example 3: free of impurities). This solution had significantly reduced impurities such as water and acetic acid.

[0624] The obtained translucent blue substance, ex-7-blue-Mat, was dissolved in a volumetric flask to a metal ion concentration of 1.50 mol / l to obtain the coating solution ex-7-coating-Sol (coating solution of Comparative Example 3).

[0625] Using the coating solution ex-7-coating-Sol and the spin coating method, a 10 × 28 × 0.50 mmt layer of LaAlO was produced with an acceleration of 10,000 rpm / s, a maximum rotation speed of 2,000 rpm, and a holding time of 60 s. ３ (100) A film was formed on an oriented single crystal to obtain a translucent blue gel film ex-7-Gel-film (the gel film of Comparative Example 3).

[0626] The obtained gel film ex-7-Gel-film was immediately placed in a furnace filled with drying gas, and organic matter was decomposed at X at 200-250°C according to the profile shown in Figure 7. The residue was removed at Y and Z at temperatures below 400°C to obtain a translucent brown calcined film ex-7-cal-film (calcined film of Comparative Example 3).

[0627] The calcined film ex-7-cal-film was calcined at 750°C in a 250 ppm oxygen-mixed argon gas using the calcination profile shown in Figure 8, resulting in the oxide thin film ex-7-oxide-YBa. ２ Cu ３ O ６．００ (YBa of Comparative Example 3) ２ Cu ３ O ６．００ ) was obtained.

[0628] Oxide thin film ex-7-oxide-YBa ２ Cu ３ O ６．００ Next, pure oxygen annealing is performed, and the oxygen count is processed to maximize the superconducting properties, resulting in the superconducting film ex-7-CARP-YBa ２ Cu ３ O ６．９３ (The superconducting film of Comparative Example 3) was obtained.

[0629] The superconducting films of Comparative Example 3 were measured using the 2θ / ω method of XRD measurement. The results were almost the same as those in Figure 15, indicating good YBa. ２ Cu ３ O ６．９３ It was found that only the (00n) peak was obtained.

[0630] In the XRD measurement of the superconducting film in Comparative Example 3, the different phase observed using the 2θ / ω method is Y, which is visible around 34 degrees. ２ O ３ And Ba can be seen at around 42 degrees. ２ CuO ３ Both were small, indicating the formation of well-oriented tissue.

[0631] The ω-scan results using the (006) peak of the superconducting film in Comparative Example 3 were almost the same as those in Figure 16. It was found that there was almost no difference in the XRD measurements.

[0632] The superconducting properties of the superconducting film in Comparative Example 3 were measured using the induction method in liquid nitrogen under its own magnetic field. In principle, the induction method requires the presence of a superconductor in a region of approximately 6 mm in diameter within the superconducting film to be evaluated. Therefore, only the properties of 4 to 6 points in the central region were obtained, but the highest value among these points was used to represent the characteristics of the superconducting film. The obtained superconducting properties were 4.87 MA / cm². ２ (77K, 0T)

[0633] J obtained in Example 6 ｃ The characteristics of Comparative Example 3 are considerably higher than those of Example 1 (77K, 0T). However, verification revealed that the measurement method and other procedures were followed correctly and there were no problems. Considering the possibility that CARP may be formed in this sample, a bridge circuit was formed in the same manner as in Example 1, and J ｃ -B-T measurement was performed.

[0634] Figure 37 shows the J of Comparative Example 3. ｃ This figure shows the measurement results of the B-T measurement. In Figure 37, the horizontal axis is the magnetic field in units of T, and the vertical axis is the logarithmic J. ｃ This is the value. Measurements were taken at 20K and 77K, with a maximum measurement of 5T. Only at 30K, measurements were taken with a magnetic field applied up to a maximum of 15T. Comparative Example 3 J ｃ The B-T measurement results are also shown in Table 1.

[0635] J of the superconducting film in Comparative Example 3 ｃ (30K, 5T) is 1.30 MA / cm ２ The values ​​were (30K, 5T). The total impurity content was calculated to be 1.636%, which is considered to be a superconducting film similar to Comparative Example 1.

[0636] Based on the results in Figure 37, it appears that CARP is not formed, or if it is formed, there is a QFG present that is too small to exert its effect. In Figure 37, the characteristics at 30K and 15T are higher than those of Comparative Example 1, but at 30K and 5T they are only slightly better, and the characteristics fall short around 30K and 2T. At least the fact that the characteristics do not improve at low temperatures and low magnetic fields indicates that the superconducting film of Comparative Example 3 does not possess the characteristics of CARP.

[0637] Furthermore, Figure 37 shows that the 3-5T characteristic at 77K is higher for the superconducting film of Comparative Example 3 than for the superconducting film of Comparative Example 0. This higher characteristic means that QFG is formed, and even if CARP is formed inside, it will not be effective. Of course, there is a possibility that CARP is formed inside the superconductor. However, it was found that QFG is formed even more so, and that the effect of CARP cannot be exerted in this superconductor.

[0638] It was found that suppressing QFG formation is important for the CARP effect to manifest. Therefore, we decided to investigate whether CARP formation is possible using Yb with a larger lattice mismatch.

[0639] (Example 8) A coating solution was prepared according to the flowchart shown in Figure 5. Here, a CARP film consisting of praseodymium, samarium, and ytterbium was formed, and it was decided to investigate whether there was any difference compared to the case of praseodymium, samarium, and thulium.

[0640] Crystalline acetates containing hydrated water were used as raw materials. Purity was calculated from the number of water molecules in crystallization obtained by thermal analysis. We prepared praseodymium acetate with a purity of 99.4%, samarium acetate with a purity of 99.4%, ytterbium acetate with a purity of 99.8%, yttrium acetate with a purity of 99.8%, barium acetate with a purity of 99.8%, and copper acetate with a purity of 99.8%. The total amount of impurities was calculated to be 0.203%.

[0641] Praseodymium acetate, samarium acetate, ytterbium acetate, yttrium acetate, barium acetate, and copper acetate are mixed in a metal ion molar ratio of 2:2:4:92:200:300, dissolved in ion-exchanged water, and an equimolar amount of CF is reacted. ３ COOH was mixed and stirred to obtain the solution ex-8-MOAc-Sol (aqueous acetate solution of Example 8) using ex-8-BaOAc.

[0642] The obtained solution, ex-8-MOAc-Sol, was placed in a round-bottom flask, and the reaction and purification were carried out under reduced pressure in a rotary evaporator for 12 hours to obtain a translucent blue substance, ex-8-blue-Mat-i (blue substance of Example 8: containing impurities).

[0643] The obtained substance ex-8-blue-Mat-i contains approximately 7 wt% water and acetic acid, which are reaction byproducts during solution synthesis. The translucent blue substance ex-8-blue-Mat-i was dissolved in 20 times its weight of anhydrous methanol to obtain a methanol solution ex-8-MeOH-Sol-i (methanol solution of Example 8: containing impurities of water and acetic acid).

[0644] The purification process shown in Figure 5h was carried out. Further purification of the methanol solution ex-8-MeOH-Sol-i yielded a translucent blue substance, ex-8-blue-Mat (the blue substance from Example 8: free of impurities). This solution had significantly reduced impurities such as water and acetic acid.

[0645] The obtained translucent blue substance, ex-8-blue-Mat, was dissolved in a volumetric flask to a metal ion concentration of 1.50 mol / l to obtain the coating solution ex-8-coating-Sol (coating solution of Example 8).

[0646] Using the coating solution ex-8-coating-Sol and the spin coating method, a 10 × 28 × 0.50 mmt layer of LaAlO was produced with an acceleration of 10,000 rpm / s, a maximum rotation speed of 2,000 rpm, and a holding time of 60 s. ３ (100) A film was formed on an oriented single crystal to obtain a translucent blue gel film ex-8-Gel-film (gel film of Example 8).

[0647] The obtained gel film, ex-8-Gel-film, was immediately placed in a furnace filled with drying gas. Organic matter was decomposed at X, 200-250°C, according to the profile shown in Figure 7, and the residue was removed at Y and Z, below 400°C, to obtain a translucent brown calcined film, ex-8-cal-film (calcined film of Example 8).

[0648] The calcined film ex-8-cal-film was calcined at 750°C in a 250 ppm oxygen-mixed argon gas using the calcination profile shown in Figure 8, resulting in the oxide thin film ex-8-oxide-YBa. ２ Cu ３ O ６．００ (YBa of Example 8) ２ Cu ３ O ６．００ ) was obtained.

[0649] Oxide thin film ex-8-oxide-YBa ２ Cu ３ O ６．００ Next, pure oxygen annealing is performed, and the oxygen count is processed to maximize the superconducting properties, resulting in the superconducting film ex-8-CARP-YBa ２ Cu ３ O ６．９３ (The superconducting film of Example 8) was obtained.

[0650] The superconducting films of Example 8 were measured using the 2θ / ω method of XRD measurement. The results were almost the same as those in Figure 15, indicating good YBa. ２ Cu ３ O ６．９３It was found that only the (00n) peak was obtained.

[0651] The XRD measurement of the superconducting film in Example 8 using the 2θ / ω method shows a different phase, with a Y-shaped phase visible around 34 degrees. ２ O ３ And Ba can be seen at around 42 degrees. ２ CuO ３ Both were small, indicating the formation of well-oriented tissue.

[0652] The ω-scan results using the (006) peak of the superconducting film in Example 8 were almost the same as those in Figure 16. It was found that there was almost no difference in the XRD measurements.

[0653] The superconducting properties of the superconducting film in Example 8 were measured using the induction method in liquid nitrogen under its own magnetic field. In principle, the induction method requires the presence of a superconductor in a region of approximately 6 mm in diameter within the superconducting film to be evaluated. Therefore, only the properties of 4 to 6 points in the central region were obtained, but the highest value among these points was used to represent the characteristics of the superconducting film. The obtained superconducting properties were 3.17 MA / cm². ２ (77K, 0T)

[0654] J ｃ The value (77K, 0T) is slightly lower compared to other examples. Originally, heavy rare earth superconductors are T ｃ It is thought that this is because the performance is low. Considering that CARP may be formed in this sample, a bridge circuit was formed in the same way as in Example 1, J ｃ -B-T measurement was performed.

[0655] J of the superconducting film in Example 8 ｃ - The B-T measurement results are shown in Table 1. ｃ (30K, 5T) is 1.74 MA / cm ２ The values ​​were (30K, 5T). The total impurity content was calculated to be 0.203%, which is considered to be a superconducting film similar to that of Example 1. The performance was one step lower than the others, and it is thought that the performance was lower than that of Er and Tm due to lattice mismatch.

[0656] Table 1 shows the α / β, α / γ, and α / δ values, which are thought to quantitatively evaluate the CARP effect of the superconducting film in Example 8. The values ​​are 8.8, 63, and 1,254, respectively. From Table 1, it can be seen that these values ​​increase when Yb is replaced by Tm and Er. The increase in values ​​is thought to be related to the decreasing size of the artificial pin. It is thought that the effect disappears at 77K as the size of the artificial pin decreases, and in that case, the α / β, α / γ, and α / δ values ​​are expected to decrease.

[0657] The raw materials used to create the superconducting film in this study were the combination with the lowest total impurity content. Despite this, the α / β, α / γ, and α / δ values ​​were smaller than those of the others. However, these values ​​were still significantly larger than the maximum values ​​of the comparative examples, which were 3.5, 7.0, and 41, respectively. Therefore, it is believed that the CARP is able to exert its intended effect.

[0658] While it is true that CARP is effective in structures where QFG is suppressed, it is likely that in some cases the α / β, α / γ, and α / δ values ​​may end up being small.

[0659] In previous examples, we have experimented by changing the elements with small ionic radii among the constituent elements of CARP, which are called Counter Atoms in CARP. Next, we decided to check whether the same effect can be obtained by changing Y, which is a Matrix Atom, to a different element.

[0660] (Examples 9A, 9B) Coating solutions were prepared according to the flowchart shown in Figure 5. Here, a CARP film consisting of praseodymium, samarium, and thulium is formed, but the matrix elements are changed from yttrium to holmium and gadolinium to investigate whether a structure that can exhibit the effects of CARP can be realized.

[0661] Some researchers might think that it's easy to replace yttrium with holmium or gadolinium, but that's only true for PLD and MOCVD methods. In the TFA-MOD method, whether the lattice grows during firing may be influenced by the magnitude of atomic vibrations. In that case, yttrium, which is atomically light in the third period, has large vibrations, while holmium and gadolinium, which are atomically heavy in the fifth period, have small vibrations, and a structure that can exhibit CARP may not be realized. That's why we conducted this investigation.

[0662] Crystalline acetates containing hydration water were prepared as raw materials. Purity was calculated from the number of water molecules in crystallization obtained by thermal analysis. The first combination of acetates consisted of praseodymium acetate (99.4% purity), samarium acetate (99.4% purity), holmium acetate (99.8% purity), thulium acetate (99.8% purity), barium acetate (99.8% purity), and copper acetate (99.8% purity). This acetate was designated as ex-9-MOAc-A (acetate of Example 9A).

[0663] The second acetate combination consists of 99.4% pure praseodymium acetate, 99.4% pure samarium acetate, 99.8% pure gadolinium acetate, 99.8% pure thulium acetate, 99.8% pure barium acetate, and 99.8% pure copper acetate. This acetate is designated as ex-9-MOAc-B (acetate of Example 9B).

[0664] Praseodymium acetate, samarium acetate, thulium acetate, holmium acetate, barium acetate, and copper acetate are mixed in a metal ion molar ratio of 2:2:4:92:200:300, dissolved in ion-exchanged water, and an equimolar amount of CF is reacted. ３ COOH was mixed and stirred to obtain the solution ex-9-MOAc-Sol-A (aqueous acetate solution of Example 9A) using ex-9-MOAc-A. The total amount of impurities was calculated to be 0.203%.

[0665] Similarly, praseodymium acetate, samarium acetate, thulium acetate, gadolinium acetate, barium acetate, and copper acetate are mixed in a metal ion molar ratio of 2:2:4:92:200:300, dissolved in ion-exchanged water, and an equimolar amount of CF is reacted. ３COOH was mixed and stirred to obtain the solution ex-9-MOAc-Sol-B (aqueous acetate solution of Example 9B) using ex-9-MOAc-B. The total elemental impurity content was calculated to be 0.203%.

[0666] The obtained solutions ex-9-MOAc-Sol-A and ex-9-MOAc-Sol-B were each placed in a round-bottom flask, and the reaction and purification were carried out under reduced pressure in a rotary evaporator for 12 hours to obtain the translucent blue substances ex-9-blue-Mat-A-i (blue substance of Example 9A: containing impurities) and ex-9-blue-Mat-B-i (blue substance of Example 9B: containing impurities), respectively.

[0667] The obtained substances ex-9-blue-Mat-A-i and ex-9-blue-Mat-B-i each contain approximately 7 wt% water and acetic acid, which are reaction byproducts during solution synthesis. The translucent blue substances ex-9-blue-Mat-A-i and ex-9-blue-Mat-B-i were dissolved in 20 times their weight in anhydrous methanol to obtain methanol solutions ex-9-MeOH-Sol-A-i (methanol solution of Example 9A: containing impurities of water and acetic acid) and ex-9-MeOH-Sol-B-i (methanol solution of Example 9B: containing impurities of water and acetic acid), respectively.

[0668] The purification process shown in Figure 5h was performed. Further purification of the methanol solutions ex-9-MeOH-Sol-A-i and ex-9-MeOH-Sol-B-i yielded translucent blue substances ex-9-blue-Mat-A (blue substance from Example 9A: no impurities) and ex-9-blue-Mat-B (blue substance from Example 9B: no impurities). These solutions had significantly reduced impurities such as water and acetic acid.

[0669] The obtained translucent blue substances, ex-9-blue-Mat-A and ex-9-blue-Mat-B, were dissolved in volumetric flasks to a metal ion concentration of 1.50 mol / l to obtain coating solutions, ex-9-coating-Sol-A (coating solution of Example 9A) and ex-9-coating-Sol-B (coating solution of Example 9B), respectively.

[0670] Using coating solutions ex-9-coating-Sol-A and ex-9-coating-Sol-B, a spin coating method was used to coat 10 × 28 × 0.50 mmt of LaAlO at an acceleration of 10,000 rpm / s, a maximum rotation speed of 2,000 rpm, and a holding time of 60 s. ３ (100) A film was formed on an oriented single crystal to obtain translucent blue gel films ex-9-Gel-film-A (gel film of Example 9A) and ex-9-Gel-film-B (gel film of Example 9B), respectively.

[0671] The obtained gel films ex-9-Gel-film-A and ex-9-Gel-film-B were immediately placed in a furnace filled with drying gas, and organic matter was decomposed at X at 200-250°C according to the profile shown in Figure 7. The residue was then removed at Y and Z at temperatures below 400°C, yielding translucent brown calcined films ex-9-cal-film-A (calcined film of Example 9A) and ex-9-cal-film-B (calcined film of Example 9B), respectively.

[0672] The calcined films ex-9-cal-film-A and ex-9-cal-film-B were calcined at 750°C in a 250 ppm oxygen-mixed argon gas using the calcination profile shown in Figure 8, resulting in the formation of the oxide thin film ex-9-oxide-HoBa ２ Cu ３ O ６．００ -A (matrix of Example 9A), and ex-9-oxide-GdBa ２ Cu ３ O ６．００ -B (matrix of Example 9B) was obtained.

[0673] Oxide thin film ex-9-oxide-HoBa ２ Cu ３ O ６．００ -A, and ex-9-oxide-GdBa ２ Cu ３ O ６．００ -B then undergoes pure oxygen annealing, and the oxygen count is processed to maximize the superconducting properties, resulting in the superconducting film ex-9-CARP-HoBa ２ Cu ３ O ６．９３ -A (superconducting film of Example 9A), and ex-9-CARP-GdBa２ Cu ３ O ６．９３ -B (the superconducting film of Example 9B) was obtained.

[0674] The superconducting films of Example 9A and Example 9B were measured using the 2θ / ω method of XRD measurement. The results were obtained from HoBa ２ Cu ３ O ６．９３ Ya GdBa ２ Cu ３ O ６．９３ Only the (00n) peak is obtained. Note that these peaks are YBa ２ Cu ３ O ６．９３ The (00n) peak appears in almost the same position, but the three strong peaks up to (007) are different. In YBCO, the (003), (005), and (006) peaks are strong, while in HoBCO and GdBCO, the three strong peaks are (001), (003), and (006).

[0675] The XRD measurements of the superconducting film in Example 9A and the superconducting film in Example 9B, using the 2θ / ω method, show different phases, both of which appear around 34 degrees (Y). ２ O ３ And Ba can be seen at around 42 degrees. ２ CuO ３ Both were small, indicating the formation of well-oriented tissue.

[0676] The ω-scan results using the (006) peak for the superconducting film of Example 9A and the superconducting film of Example 9B were also almost identical to those in Figure 16. It was found that there was almost no difference in the XRD measurements.

[0677] The superconducting properties of the superconducting films of Example 9A and Example 9B were measured in liquid nitrogen under a self-magnetic field using the induction method. In principle, the induction method requires the presence of superconductors in a region of approximately 6 mm in diameter within the superconducting film to be evaluated. Therefore, only the properties of 4 to 6 points in the central region were obtained, but the highest value among these points was used to represent the characteristics of the superconducting film. The obtained superconducting properties were 3.82 MA / cm². ２ (77K, 0T), and 3.78 MA / cm ２ (77K, 0T)

[0678] J ｃ The value (77K, 0T) is almost the same as the result when MA is Y. We considered the possibility that the superconducting properties are determined by the matrix element, but no significant difference was observed. We considered that this sample may have CARP formation, and similar to Example 1, we formed a bridge circuit with the superconducting film of Example 9A and the superconducting film of Example 9B, and J ｃ -B-T measurement was performed.

[0679] The measurement results for the superconducting film of Example 9A and the superconducting film of Example 9B are shown in Table 1. ｃ (30K, 5T) are 2.06 MA / cm, respectively. ２ (30K, 5T), and 2.08 MA / cm ２ The temperature was (30K, 5T). The total impurity content was calculated to be 0.203%, which is considered to be a superconducting film similar to that of Example 1.

[0680] Table 1 shows the α / β, α / γ, and α / δ values, which are thought to quantitatively evaluate the effect of the superconducting films of Example 9A and Example 9B on CARP formation. The values ​​for the superconducting film of Example 9A were 13.6, 108, and 1,732, respectively. The values ​​for the superconducting film of Example 9B were 13.8, 112, and 1,776, respectively. These results are close to the values ​​obtained for the superconducting film in Example 1.

[0681] CARP formation is induced by small lattice mismatches. Furthermore, Examples 9A and 9B use holmium and gadolinium from the fifth period instead of yttrium from the third period. Therefore, it was hypothesized that the difference in atomic vibrations would increase heterogeneity, leading to an increase in QFG levels and a decrease in α / β, α / γ, and α / δ values. However, this was not the case. While yttrium is often considered to have atomic relationships similar to holmium, these experimental results demonstrate that QFG is suppressed in the same way, and the CARP effect can still be obtained.

[0682] Next, we decided to investigate whether the α / β, α / γ, and α / δ values ​​could be maintained and the CARP effect obtained in the same way when Sm, which is considered a supporting element in CARP, was replaced with another element. We conducted the experiment by replacing Sm with Nd.

[0683] (Example 10) A coating solution was prepared according to the flowchart shown in Figure 5. Here, a CARP film consisting of praseodymium, neodymium, and thulium was formed, and it was decided to investigate whether there was any difference compared to the case of praseodymium, samarium, and thulium.

[0684] Crystalline acetates containing hydration water were prepared as raw materials. Purity was calculated from the number of water molecules in crystallization obtained by thermal analysis. We prepared praseodymium acetate with a purity of 99.4%, neodymium acetate with a purity of 99.4%, thulium acetate with a purity of 99.8%, yttrium acetate with a purity of 99.8%, barium acetate with a purity of 99.8%, and copper acetate with a purity of 99.8%. The total amount of impurities was calculated to be 0.203%. Neodymium is thought to be an element that decays easily, similar to praseodymium and samarium, and white decomposition products accumulate on the surface over time. Light rare earth elements have a large ionic radius and generally decompose quickly.

[0685] Praseodymium acetate, neodymium acetate, thulium acetate, yttrium acetate, barium acetate, and copper acetate are mixed in a metal ion molar ratio of 2:2:4:92:200:300, dissolved in ion-exchanged water, and an equimolar amount of CF is reacted. ３ COOH was mixed and stirred to obtain the solution ex-10-MOAc-Sol (aqueous acetate solution of Example 10) using ex-10-BaOAc.

[0686] The obtained solution, ex-10-MOAc-Sol, was placed in a round-bottom flask, and the reaction and purification were carried out under reduced pressure in a rotary evaporator for 12 hours to obtain a translucent blue substance, ex-10-blue-Mat-i (blue substance of Example 10: containing impurities).

[0687] The obtained substance ex-10-blue-Mat-i contains approximately 7 wt% water and acetic acid, which are reaction byproducts during solution synthesis. The translucent blue substance ex-10-blue-Mat-i was dissolved in 20 times its weight of anhydrous methanol to obtain a methanol solution ex-10-MeOH-Sol-i (methanol solution of Example 10: containing impurities of water and acetic acid).

[0688] The purification process shown in Figure 5h was performed. Further purification of the methanol solution ex-10-MeOH-Sol-i yielded a translucent blue substance, ex-10-blue-Mat (the blue substance from Example 10: free of impurities). This solution had significantly reduced impurities such as water and acetic acid.

[0689] The obtained translucent blue substance, ex-10-blue-Mat, was dissolved in a volumetric flask to a metal ion concentration of 1.50 mol / l to obtain the coating solution ex-10-coating-Sol (coating solution of Example 10).

[0690] Using the coating solution ex-10-coating-Sol and the spin coating method, a 10 × 28 × 0.50 mmt layer of LaAlO was produced with an acceleration of 10,000 rpm / s, a maximum rotation speed of 2,000 rpm, and a holding time of 60 s. ３ (100) A film was formed on an oriented single crystal to obtain a translucent blue gel film ex-10-Gel-film (gel film of Example 10).

[0691] The obtained gel film ex-10-Gel-film was immediately placed in a furnace filled with drying gas, and organic matter was decomposed at X at 200-250°C according to the profile shown in Figure 7. The residue was removed at Y and Z at temperatures below 400°C to obtain a translucent brown calcined film ex-10-cal-film (calcined film of Example 10).

[0692] The calcined film ex-10-cal-film was calcined at 750°C in 250 ppm oxygen-mixed argon gas using the calcination profile shown in Figure 8, resulting in the oxide thin film ex-10-oxide-YBa ２ Cu ３ O ６．００ (YBa of Example 10) ２ Cu ３ O ６．００ ) was obtained.

[0693] Oxide thin film ex-10-oxide-YBa ２ Cu ３ O ６．００ Next, pure oxygen annealing is performed, and the oxygen count is processed to maximize the superconducting properties, resulting in the superconducting film ex-10-CARP-YBa ２ Cu ３ O ６．９３ (The superconducting film of Example 10) was obtained.

[0694] The superconducting films of Example 10 were measured using the 2θ / ω method of XRD measurement. The results were almost the same as those in Figure 15, indicating good YBa. ２ Cu ３ O ６．９３ It was found that only the (00n) peak was obtained.

[0695] The XRD measurement of the superconducting film in Example 10 using the 2θ / ω method shows a different phase, with a Y-shaped phase appearing around 34 degrees. ２ O ３ And Ba can be seen at around 42 degrees. ２ CuO ３ Both were small, indicating the formation of well-oriented tissue.

[0696] The ω-scan results using the (006) peak of the superconducting film in Example 10 were almost the same as those in Figure 16. It was found that there was almost no difference in the XRD measurements.

[0697] The superconducting properties of the superconducting film in Example 10 were measured using the induction method in liquid nitrogen under its own magnetic field. In principle, the induction method requires the presence of a superconductor in a region of approximately 6 mm in diameter within the superconducting film to be evaluated. Therefore, only the properties of 4 to 6 points in the central region were obtained, but the highest value among these points was used to represent the characteristics of the superconducting film. The obtained superconducting properties were 3.34 MA / cm². ２ (77K, 0T)

[0698] J ｃThe values ​​(77K, 0T) for Example 10 are slightly lower compared to the other samples. This is surprising, as we expected the characteristics to improve by using Nd instead of Sm, but it could be due to insufficient investigation of the conditions or a deviation from the optimal point. We consider that this sample may have CARP formation, and we formed a bridge circuit similar to Example 1, J ｃ -B-T measurement was performed.

[0699] J of the superconducting film in Example 10 ｃ - The B-T measurement results are shown in Table 1. ｃ (30K, 5T) is 1.67 MA / cm ２ The temperature was (30K, 5T). The total impurity content was calculated to be 0.203%, which is considered to be a superconducting film similar to that of Example 1. Overall, the performance results were somewhat low. It was thought that changing Sm to Nd would improve the performance, but since everything changed for the worse, it is possible that some condition is lacking, which may be causing an increase in the amount of QFG formation.

[0700] Table 1 shows the α / β, α / γ, and α / δ values, which are thought to quantitatively evaluate the CARP effect of the superconducting film in Example 10. The values ​​are 7.4, 69, and 892, respectively. Although the values ​​are generally low, it is clear that values ​​that could not be achieved in the comparative examples have been obtained.

[0701] CARP requires Matrix Atoms (medium size), Pin Atoms (large size, Pr only), and Counter Atoms (small size). However, currently, CARP is often formed better when Supporting Atoms, another large size, are present. Examples 1 to 10 all involved creating CARP using these four types of elements.

[0702] To investigate whether it is possible to reduce the amount of QFG and achieve good α / β, α / γ, and α / δ values ​​in CARP made from three elements, which have so far exhibited some effect despite their low properties, we next conducted an investigation using CARP without supporting elements.

[0703] (Example 11) A coating solution was prepared according to the flowchart shown in Figure 5. Here, gadolinium was used as the matrix element, and a CARP film consisting of praseodymium and thulium was formed.

[0704] Crystalline acetates containing hydrated water were prepared as raw materials. Purity was calculated from the number of water molecules in crystallization obtained by thermal analysis. We prepared praseodymium acetate with a purity of 99.4%, gadolinium acetate with a purity of 99.8%, thulium acetate with a purity of 99.8%, barium acetate with a purity of 99.8%, and copper acetate with a purity of 99.8%.

[0705] Praseodymium acetate, thulium acetate, yttrium acetate, barium acetate, and copper acetate are mixed in a metal ion molar ratio of 4:4:92:200:300, dissolved in ion-exchanged water, and an equimolar amount of CF is reacted. ３ The mixture was mixed with COOH and stirred to obtain the solution ex-11-MOAc-Sol (aqueous acetate solution of Example 11).

[0706] The obtained solution, ex-11-MOAc-Sol, was placed in a round-bottom flask, and the reaction and purification were carried out under reduced pressure in a rotary evaporator for 12 hours to obtain the translucent blue substance ex-11-blue-Mat-i (blue substance of Example 11: containing impurities).

[0707] The obtained substance ex-11-blue-Mat-i contains approximately 7 wt% water and acetic acid, which are reaction byproducts during solution synthesis. The translucent blue substance ex-11-blue-Mat-i was dissolved in 20 times its weight of anhydrous methanol to obtain a methanol solution ex-11-MeOH-Sol-i (methanol solution of Example 11: containing impurities of water and acetic acid).

[0708] The purification process shown in Figure 5h was performed. Further purification of the methanol solution ex-11-MeOH-Sol-i yielded a translucent blue substance, ex-11-blue-Mat (the blue substance from Example 11: free of impurities). This solution had significantly reduced impurities such as water and acetic acid.

[0709] The obtained translucent blue substance, ex-11-blue-Mat, was dissolved in a volumetric flask to a metal ion concentration of 1.50 mol / l to obtain the coating solution ex-11-coating-Sol (coating solution of Example 11).

[0710] Using the coating solution ex-11-coating-Sol and the spin coating method, a 10 × 28 × 0.50 mmt layer of LaAlO was produced with an acceleration of 10,000 rpm / s, a maximum rotation speed of 2,000 rpm, and a holding time of 60 s. ３ (100) A film was formed on an oriented single crystal to obtain a translucent blue gel film ex-11-Gel-film (gel film of Example 11).

[0711] The obtained gel film ex-11-Gel-film was immediately placed in a furnace filled with drying gas, and organic matter was decomposed at X at 200-250°C according to the profile shown in Figure 7. The residue was removed at Y and Z below 400°C to obtain a translucent brown calcined film ex-11-cal-film (calcined film of Example 11).

[0712] The calcined film ex-11-cal-film was calcined at 750°C in a 250 ppm oxygen-mixed argon gas using the calcination profile shown in Figure 8, resulting in the oxide thin film ex-11-oxide-GdBa ２ Cu ３ O ６．００ (Matrix GdBa of Example 11) ２ Cu ３ O ６．００ ) was obtained.

[0713] Oxide thin film ex-11-oxide-GdBa ２ Cu ３ O ６．００ Next, pure oxygen annealing is performed, and the oxygen count is processed to maximize the superconducting properties, resulting in the superconducting film ex-11-CARP-GdBa ２ Cu ３ O ６．９３ (A CARP-containing superconducting film of Example 11) was obtained.

[0714] The superconducting films of Example 11 were measured using the 2θ / ω method of XRD measurement. The results were almost the same as those in Figure 15, indicating good GdBa. ２ Cu ３ O６．９３ It was found that only the (00n) peak was obtained.

[0715] The XRD measurement of the superconducting film in Example 11 shows a different phase in the 2θ / ω method, with a Y-shaped phase visible around 34 degrees. ２ O ３ And Ba can be seen at around 42 degrees. ２ CuO ３ Both were small, indicating the formation of well-oriented tissue.

[0716] The ω-scan results using the (006) peak of the superconducting film in Example 11 were almost the same as those in Figure 16. It was found that there was almost no difference in the XRD measurements.

[0717] The superconducting properties of the superconducting film in Example 11 were measured using the induction method in liquid nitrogen under its own magnetic field. In principle, the induction method requires the presence of a superconductor in a region of approximately 6 mm in diameter within the superconducting film to be evaluated. Therefore, only the properties of 4 to 6 points in the central region were obtained, but the highest value among these points was used to represent the characteristics of the superconducting film. The obtained superconducting property was 1.89 MA / cm². ２ (77K, 0T)

[0718] J ｃ The values ​​(77K, 0T) for Example 11 are considerably lower than those of other samples. Although this is a CARP without supporting atoms, there is a possibility that the CARP elements have not clustered properly. To investigate whether CARP has formed in this sample, a bridge circuit was formed in the same manner as in Example 1, and J ｃ -B-T measurement was performed.

[0719] J of the superconducting film in Example 11 ｃ - The B-T measurement results are shown in Table 1. ｃ (30K, 5T) is 1.40 MA / cm ２ The temperature was (30K, 5T). The total impurity content was calculated to be 0.203%, which should have resulted in a good superconducting film similar to Example 1, but the performance was poor.

[0720] Table 1 shows the α / β, α / γ, and α / δ values, which are thought to quantitatively evaluate the CARP effect of the superconducting film in Example 11. The values ​​are 6.4, 19, and 206, respectively. These are generally low values. However, these values ​​were not achieved in the comparative examples, suggesting that there is room for improvement in the future through optimization of conditions, etc.

[0721] Although the degree of improvement in properties is relatively small, it appears that we were able to create a structure in which QFG was suppressed to some extent during CARP formation without using Supporting Atoms.

[0722] Next, we investigated whether mixing multiple supporting atoms in a CARP (Carbonated Activated Polymer) composed of four elements would be effective.

[0723] (Examples 12A, 12B, 12C) Coating solutions were prepared according to the flowchart shown in Figure 5. Here, for CARP made from praseodymium, samarium, and thulium, we investigated whether it was possible to create a structure in which QFG formation could be suppressed and the effects of CARP could be obtained by forming a film with a mixture of neodymium and samarium in the samarium portion.

[0724] Crystalline acetates containing hydration water were prepared as raw materials. Purity was calculated from the number of water molecules in crystallization obtained by thermal analysis. We prepared praseodymium acetate with a purity of 99.4%, neodymium acetate with a purity of 99.4%, samarium acetate with a purity of 99.4%, thulium acetate with a purity of 99.8%, yttrium acetate with a purity of 99.8%, barium acetate with a purity of 99.8%, and copper acetate with a purity of 99.8%.

[0725] Praseodymium acetate, neodymium acetate, samarium acetate, thulium acetate, yttrium acetate, barium acetate, and copper acetate were mixed in the following ways: the first mixture had a metal ion molar ratio of 2:1:1:4:92:200:300; the second mixture had a metal ion molar ratio of 2:0.6:1.4:4:92:200:300; and the third mixture had a metal ion molar ratio of 2:0.2:1.8:4:92:200:300. Mixed acetates ex-12-MOAcs-A (mixed acetate of Example 12A), ex-12-MOAcs-B (mixed acetate of Example 12B), and ex-12-MOAcs-C (mixed acetate of Example 12C), respectively.

[0726] The resulting mixed acetic acids ex-12-MOAcs-A, ex-12-MOAcs-B, and ex-12-MOAcs-C are each dissolved in ion-exchanged water, and an equimolar amount of CF is reacted. ３ COOH was mixed and stirred to obtain solutions ex-12-MOAc-Sol-A (aqueous acetate solution of Example 12A), ex-12-MOAc-Sol-B (aqueous acetate solution of Example 12B), and ex-12-MOAc-Sol-C (aqueous acetate solution of Example 12C).

[0727] The obtained solutions ex-12-MOAc-Sol-A, ex-12-MOAc-Sol-B, and ex-12-MOAc-Sol-C were each placed in a round-bottom flask, and the reaction and purification were carried out under reduced pressure in a rotary evaporator for 12 hours to obtain the translucent blue substances ex-12-blue-Mat-A-i (blue substance of Example 12A: containing impurities), ex-12-blue-Mat-B-i (blue substance of Example 12B: containing impurities), and ex-12-blue-Mat-C-i (blue substance of Example 12C: containing impurities).

[0728] The obtained substances ex-12-blue-Mat-A-i, ex-12-blue-Mat-B-i, and ex-12-blue-Mat-C-i contain approximately 7 wt% of water and acetic acid, which are reaction byproducts during solution synthesis. The translucent blue substances ex-12-blue-Mat-A-i, ex-12-blue-Mat-B-i, and ex-12-blue-Mat-C-i were each dissolved in 20 times their w...

Claims

1. An oxide superconducting layer having a first surface and a second surface facing the first surface, and including a first region and a second region, The first region has a continuous perovskite structure and contains rare earth elements, barium (Ba), and copper (Cu), wherein the rare earth elements include a first element which is praseodymium (Pr), at least one second element selected from the group consisting of neodymium (Nd), samarium (Sm), and europium (Eu), at least one third element selected from the group consisting of yttrium (Y), europium (Eu), gadolinium (Gd), dysprosium (Dy), holmium (Ho), and erbium (Er), and at least one fourth element selected from the group consisting of yttrium (Y), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu), and the first element, the second element The element, the third element, and the fourth element are all different elements, and if the third and fourth elements are not yttrium (Y), the atomic number of the second element is smaller than the atomic number of the third element, and the atomic number of the third element is smaller than the atomic number of the fourth element, and if the third element is yttrium (Y), the fourth element is at least one element selected from the group consisting of erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu), and if the fourth element is yttrium (Y), the atomic number of the second element is smaller than the atomic number of the third element, and the third element is at least one element selected from the group consisting of europium (Eu), gadolinium (Gd), and dysprosium (Dy), An oxide superconductor comprising an oxide superconducting layer in which the second region is amorphous or polycrystalline and includes a first portion extending in a first direction parallel to the second surface and a second portion extending in a second direction parallel to the second surface and intersecting the first direction, and the volume ratio of the second region is 0.001% or more and 1.10% or less.

2. In the first region, the ratio of the atomic concentration of the third element to the sum of the atomic concentrations of the first element, the second element, the third element, and the fourth element is 60% or more, the oxide superconductor according to claim 1.

3. The oxide superconductor according to claim 1, wherein the depth of the second region in the direction from the second surface toward the first surface is 10% or less of the thickness of the oxide superconducting layer.

4. The oxide superconductor according to claim 1, wherein the width of the first portion on the second surface is 10 nm or less, and the width of the second portion on the second surface is 10 nm or less.

5. The oxide superconductor according to claim 1, wherein the area ratio of the second region on the second surface is 10% or less.

6. The oxide superconductor according to claim 1, wherein the second region contains barium (Ba).

7. The oxide superconductor according to claim 1, wherein the second region is provided along a low-angle grain boundary of the first region.

8. The oxide superconductor according to claim 1, wherein, in the second surface, the first region includes a first block in which the a-axis of the perovskite structure is oriented in one direction and a second block in which the a-axis of the perovskite structure is oriented in a direction intersecting the aforementioned one direction, and at least a portion of the second region is provided at the boundary between the first block and the second block.

9. The oxide superconductor according to claim 1, wherein the first region includes a portion of the cross-section of the oxide superconducting layer that contains the first element, the second element, and the fourth element and is 10 nm square or smaller.

10. The first region contains fluorine (F), and the atomic concentration of fluorine (F) is 2.0 × 10⁻¹⁶ １５ atoms / cm ３ The above 5.0 x 10 １９ atoms / cm ３ The above is true, and the first region contains carbon (C), and the atomic concentration of carbon (C) is 1.0 × 10⁻¹⁴. １７ atoms / cm ３ The above 5.0 x 10 ２０ atoms / cm ３ The oxide superconductor according to claim 1 is as described above.

11. The oxide superconductor according to claim 1, further comprising: a substrate provided on the side of the first surface of the oxide superconducting layer; and a metal layer provided on the side of the second surface of the oxide superconducting layer.

12. An oxide superconducting layer having a first surface and a second surface facing the first surface, and including a first region and a second region, wherein the first region has a continuous perovskite structure and contains a rare earth element, barium (Ba), and copper (Cu), and the rare earth element is at least one second element selected from the group consisting of praseodymium (Pr) as a first element, neodymium (Nd), samarium (Sm), and europium (Eu), at least one third element selected from the group consisting of yttrium (Y), europium (Eu), gadolinium (Gd), dysprosium (Dy), holmium (Ho), and erbium (Er), and at least one fourth element selected from the group consisting of yttrium (Y), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu), and the first element, the second element, the third element, and the fourth element are all different elements, and when the third element and the fourth element are not yttrium (Y), the atomic number of the second element is smaller than the atomic number of the third element, the atomic number of the third element is smaller than the atomic number of the fourth element, when the third element is yttrium (Y), the fourth element is at least one element selected from the group consisting of erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu), and when the fourth element is yttrium (Y), the atomic number of the second element is smaller than the atomic number of the third element, and the third element is at least one element selected from the group consisting of europium (Eu), gadolinium (Gd), and dysprosium (Dy), the second region is amorphous or polycrystalline, and on the second surface, includes a first portion extending in a first direction parallel to the second surface and a second portion different from the first portion and extending in a second direction parallel to the second surface and intersecting the first direction, the critical current density obtained when a magnetic field of 0.5 T, 2.0 T, 3.0 T, and 5.0 T is applied at a temperature of 77 K in the direction from the first surface to the second surface is respectively α (MA / cm ２ ), β (MA / cm ２ ), γ (MA / cm ２ ), and δ(MA / cm ２ An oxide superconductor comprising an oxide superconducting layer such that, when α / β > 4.0, α / γ > 10, or α / δ > 70, at least one of these inequalities holds.

13. The oxide superconductor according to claim 12, wherein at least one of the following inequalities holds: α / β > 6.0, α / γ > 20, or α / δ > 200.

14. The oxide superconductor according to claim 12, wherein at least one of the following inequalities holds: α / β > 10, α / γ > 40, or α / δ > 1000.

15. In the first region, the ratio of the atomic concentration of the third element to the sum of the atomic concentrations of the first element, the second element, the third element, and the fourth element is 60% or more, the oxide superconductor according to claim 12.

16. The oxide superconductor according to claim 12, wherein the second region contains barium (Ba).

17. An oxide superconducting layer having a first surface and a second surface facing the first surface, comprising a first region and a second region, wherein the first region has a continuous perovskite structure and comprises a rare earth element, barium (Ba), and copper (Cu), the rare earth element comprising a first element which is praseodymium (Pr), at least one second element selected from the group consisting of yttrium (Y), europium (Eu), gadolinium (Gd), dysprosium (Dy), holmium (Ho), and erbium (Er), and at least one third element selected from the group consisting of yttrium (Y), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu), and the first element The second element and the third element are all different elements, and if the second and third elements are not yttrium (Y), the atomic number of the second element is smaller than the atomic number of the third element, and if the second element is yttrium (Y), the third element is at least one element selected from the group consisting of erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu), and if the third element is yttrium (Y), the second element is at least one element selected from the group consisting of europium (Eu), gadolinium (Gd), and dysprosium (Dy), An oxide superconductor comprising an oxide superconducting layer in which the second region is amorphous or polycrystalline and includes a first portion extending in a first direction parallel to the first plane and a second portion extending in a second direction parallel to the first plane and intersecting the first direction, and the volume ratio of the second region is 0.001% or more and 1.10% or less.

18. An oxide superconducting layer having a first surface and a second surface facing the first surface, comprising a first region and a second region, wherein the first region has a continuous perovskite structure and comprises a rare earth element, barium (Ba), and copper (Cu), the rare earth element comprising a first element which is praseodymium (Pr), at least one second element selected from the group consisting of yttrium (Y), europium (Eu), gadolinium (Gd), dysprosium (Dy), holmium (Ho), and erbium (Er), and at least one third element selected from the group consisting of yttrium (Y), dysprosium (Dy), holmium (Ho), and erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu), and the first element The element, the second element, and the third element are all different elements, and if the second and third elements are not yttrium (Y), the atomic number of the second element is smaller than the atomic number of the third element, and if the second element is yttrium (Y), the third element is at least one element selected from the group consisting of erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu), and if the third element is yttrium (Y), the second element is at least one element selected from the group consisting of europium (Eu), gadolinium (Gd), and dysprosium (Dy), The second region is amorphous or polycrystalline, and the second surface includes a first portion extending in a first direction parallel to the first surface and a second portion extending in a second direction parallel to the first surface and intersecting the first direction, unlike the first portion, and the critical current densities obtained when magnetic fields of 0.5 T, 2.0 T, 3.0 T, and 5.0 T are applied in the direction from the first surface toward the second surface at a temperature of 77 K are given by α (MA / cm²), respectively. ２ ), β(MA / cm ２ ), γ (MA / cm ２ ), and δ(MA / cm ２ An oxide superconductor comprising an oxide superconducting layer such that, when α / β > 4.0, α / γ > 10, or α / δ > 70, at least one of these inequalities holds.

19. A method for manufacturing an oxide superconductor, comprising: preparing a coating solution using a rare earth element acetate, barium (Ba) acetate, copper (Cu) acetate, and trifluoroacetic acid; applying or injecting the coating solution onto a substrate to form a gel film; performing calcination on the gel film at a temperature of 400°C or lower to form a calcined film; performing final calcination on the calcined film at a temperature of 725°C to 800°C under a humidified atmosphere, and performing oxygen annealing to form an oxide superconducting layer, wherein barium acetate hydrate is used as the barium (Ba) acetate.

20. The rare earth elements include a first element which is praseodymium (Pr), at least one second element selected from the group consisting of neodymium (Nd), samarium (Sm), and europium (Eu), at least one third element selected from the group consisting of yttrium (Y), europium (Eu), gadolinium (Gd), dysprosium (Dy), holmium (Ho), and erbium (Er), and at least one fourth element selected from the group consisting of yttrium (Y), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu), wherein the first element, the second element, the third element, and the fourth element are all different elements, and the third element A method for manufacturing an oxide superconductor according to claim 19, wherein if the second element and the fourth element are not yttrium (Y), the atomic number of the second element is smaller than the atomic number of the third element, and the atomic number of the third element is smaller than the atomic number of the fourth element; if the third element is yttrium (Y), the fourth element is at least one element selected from the group consisting of erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu); if the fourth element is yttrium (Y), the atomic number of the second element is smaller than the atomic number of the third element, and the third element is at least one element selected from the group consisting of europium (Eu), gadolinium (Gd), and dysprosium (Dy).

21. The rare earth elements include a first element which is praseodymium (Pr), at least one second element selected from the group consisting of yttrium (Y), europium (Eu), gadolinium (Gd), dysprosium (Dy), holmium (Ho), and erbium (Er), and at least one third element selected from the group consisting of yttrium (Y), dysprosium (Dy), holmium (Ho), and erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu), wherein the first element, the second element, and the third element are all different elements, and the second element A method for manufacturing an oxide superconductor according to claim 19, wherein if the second element and the third element are not yttrium (Y), the atomic number of the second element is smaller than the atomic number of the third element; if the second element is yttrium (Y), the third element is at least one element selected from the group consisting of erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu); and if the third element is yttrium (Y), the second element is at least one element selected from the group consisting of europium (Eu), gadolinium (Gd), and dysprosium (Dy).

22. A method for manufacturing an oxide superconductor, comprising: preparing a coating solution using rare earth element acetates, barium (Ba) acetate, and copper (Cu) acetate, and trifluoroacetic acid; applying or injecting the coating solution onto a substrate to form a gel film; performing calcination on the gel film at a temperature of 400°C or lower to form a calcined film; performing final calcination on the calcined film at a temperature of 725°C to 800°C under a humidified atmosphere, and performing oxygen annealing to form an oxide superconducting layer, wherein the rare earth element acetates, barium (Ba) acetate, and copper (Cu) acetate are all in a crystalline state, and the total amount of impurities of the rare earth element acetates, barium (Ba) acetate, and copper (Cu) acetate is 1.10 mol% or less.

23. The rare earth elements include a first element which is praseodymium (Pr), at least one second element selected from the group consisting of neodymium (Nd), samarium (Sm), and europium (Eu), at least one third element selected from the group consisting of yttrium (Y), europium (Eu), gadolinium (Gd), dysprosium (Dy), holmium (Ho), and erbium (Er), and at least one fourth element selected from the group consisting of yttrium (Y), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu), wherein the first, second, third, and fourth elements are all different elements, and the third element A method for manufacturing an oxide superconductor according to claim 22, wherein if the second and fourth elements are not yttrium (Y), the atomic number of the second element is smaller than the atomic number of the third element, and the atomic number of the third element is smaller than the atomic number of the fourth element; if the third element is yttrium (Y), the fourth element is at least one element selected from the group consisting of erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu); if the fourth element is yttrium (Y), the atomic number of the second element is smaller than the atomic number of the third element, and the third element is at least one element selected from the group consisting of europium (Eu), gadolinium (Gd), and dysprosium (Dy).

24. The rare earth elements include a first element which is praseodymium (Pr), at least one second element selected from the group consisting of yttrium (Y), europium (Eu), gadolinium (Gd), dysprosium (Dy), holmium (Ho), and erbium (Er), and at least one third element selected from the group consisting of yttrium (Y), dysprosium (Dy), holmium (Ho), and erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu), wherein the first element, the second element, and the third element are all different elements, and the second element A method for manufacturing an oxide superconductor according to claim 22, wherein if the second element and the third element are not yttrium (Y), the atomic number of the second element is smaller than the atomic number of the third element; if the second element is yttrium (Y), the third element is at least one element selected from the group consisting of erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu); and if the third element is yttrium (Y), the second element is at least one element selected from the group consisting of europium (Eu), gadolinium (Gd), and dysprosium (Dy).

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