Superconducting wires and superconducting coils

Abstract

This superconducting wire material comprises: a superconducting layered body that has a metal substrate and an oxide superconducting layer; and a stabilizing part which is formed so as to cover the superconducting layered body and which has a larger coefficient of thermal expansion than the metal substrate. The superconducting layered body includes: a first primary surface that is a surface on the side on which the oxide superconducting layer is provided; and a second primary surface that is a surface on the side on which the metal substrate is provided. The stabilizing part includes: a first section which faces the first primary surface; and a second section which faces the second primary surface. The thickness of the second section is greater than the thickness of the first section.

Description

Technical Field

[0001] The present invention relates to superconducting wires and superconducting coils. This application claims priority based on Japanese Patent Application No. 2021-137967 filed in Japan on August 26, 2021, and incorporates the content herein by reference.

Background Art

[0002] The superconducting wire described in Patent Document 1 includes a laminate in which a substrate, an intermediate layer, an oxide superconducting layer, and a protective layer are laminated, a stabilizing layer covering the laminate, and a metal tape formed on one surface of the stabilizing layer. The metal tape is formed on the surface of the laminate on the side where the oxide superconducting layer is formed, out of the two surfaces of the stabilizing layer. The substrate is formed of, for example, Hastelloy (registered trademark). The stabilizing layer and the metal tape are formed of, for example, copper.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When the superconducting wire shrinks due to a temperature change, the oxide superconducting layer may be damaged and the superconducting characteristics may deteriorate. For example, when the superconducting wire is cooled to a temperature below the critical temperature (in the case of a Y-based superconducting wire, about 90 K or lower), the superconducting wire contracts and shear stress due to the difference in the coefficient of thermal expansion between the substrate (Hastelloy (registered trademark)) and the stabilizing layer and the metal tape (both made of copper) is applied to the oxide superconducting layer. As a result, the oxide superconducting layer may be damaged and the characteristics of the superconducting wire may deteriorate.

[0005] One aspect of the present invention is to provide a superconducting wire and a superconducting coil in which a decrease in superconducting characteristics due to a temperature change hardly occurs. [Means for solving the problem]

[0006] A superconducting wire according to one aspect of the present invention comprises a superconducting laminate having a metal substrate and an oxide superconducting layer, and a stabilizing portion formed covering the superconducting laminate and having a greater coefficient of thermal expansion than the metal substrate, wherein the superconducting laminate has a first main surface which is the side on which the oxide superconducting layer is provided and a second main surface which is the side on which the metal substrate is provided, and the stabilizing portion has a first portion facing the first main surface and a second portion facing the second main surface, wherein the thickness of the second portion is greater than the thickness of the first portion.

[0007] According to the above embodiment of the present invention, since the second portion of the stabilizing part is thicker than the first portion, even if the stabilizing part shrinks due to temperature changes, shear stress is less likely to act on the oxide superconducting layer. Therefore, damage to the oxide superconducting layer can be suppressed. Thus, the deterioration of the superconducting properties of the superconducting wire can be suppressed.

[0008] The difference between the thickness of the first portion and the thickness of the second portion may be greater than the thickness of the metal substrate.

[0009] The stabilization portion may include a first stabilization layer surrounding the superconducting laminate and a second stabilization layer formed of a metal tape and bonded to the portion of the first stabilization layer facing the second main surface.

[0010] The oxide superconducting layer may have non-oriented regions extending in the longitudinal direction of the oxide superconducting layer.

[0011] Another embodiment of the present invention provides a superconducting coil comprising the superconducting wire, wherein the superconducting wire is wound such that the first portion is located radially inward from the second portion. [Effects of the Invention]

[0012] According to one aspect of the present invention, it is possible to provide a superconducting wire and a superconducting coil in which a decrease in superconducting characteristics due to temperature change hardly occurs.

Brief Description of the Drawings

[0013] [Figure 1] It is a cross-sectional view of the oxide superconducting wire of the first embodiment. [Figure 2] It is a schematic view of the superconducting coil of the first embodiment. [Figure 3] It is a cross-sectional view of the oxide superconducting wire of the second embodiment. [Figure 4] It is a cross-sectional view of the oxide superconducting wire of a modified example of the first embodiment.

Modes for Carrying Out the Invention

[0014] Hereinafter, the present invention will be described based on preferred embodiments with reference to the drawings.

[0015] [Oxide Superconducting Wire] (First Embodiment) FIG. 1 is a cross-sectional view of an oxide superconducting wire 10 according to the first embodiment. FIG. 1 is a cross-sectional view perpendicular to the longitudinal direction of the oxide superconducting wire 10.

[0016] As shown in FIG. 1, the oxide superconducting wire 1 is provided with a superconducting laminate 5 and a stabilizing portion 6. The oxide superconducting wire 10 is a specific example of a "superconducting wire".

[0017] The superconducting laminate 5 includes a metal substrate 1, an intermediate layer 2, an oxide superconducting layer 3, and a protective layer 4. The superconducting laminate 5 has a structure in which the oxide superconducting layer 3 and the protective layer 4 are formed on the metal substrate 1 via the intermediate layer 2. That is, the superconducting laminate 5 has a configuration in which the intermediate layer 2, the oxide superconducting layer 3, and the protective layer 4 are laminated in this order on one surface of the tape-shaped metal substrate 1.

[0018] The oxide superconducting wire 10 is formed in a tape shape. In the following description, the thickness direction of the oxide superconducting wire 10 is referred to as the thickness direction Y. The thickness direction Y is the direction in which the metal substrate 1, the intermediate layer 2, the oxide superconducting layer 3, and the protective layer 4 are laminated. Along the thickness direction Y, the direction from the metal substrate 1 toward the oxide superconducting layer 3 is referred to as upward, and the opposite direction is referred to as downward. The width direction of the oxide superconducting wire 10 is referred to as the width direction X. The width direction X is a direction orthogonal to the longitudinal direction and the thickness direction of the oxide superconducting wire 10.

[0019] The metal substrate 1 is made of metal. Specific examples of the metal constituting the metal substrate 1 include nickel alloys such as Hastelloy (registered trademark); stainless steel; and oriented Ni-W alloys in which a structure is introduced into a nickel alloy. The thickness of the metal substrate 1 may be appropriately adjusted according to the purpose, and is, for example, in the range of 10 to 500 μm. One surface of the metal substrate 1 (the surface on which the intermediate layer 2 is formed) is referred to as the first surface 1a, and the surface opposite to the first surface 1a is referred to as the second surface 1b.

[0020] The intermediate layer 2 is provided between the metal substrate 1 and the oxide superconducting layer 3. The intermediate layer 2 is formed on the first surface 1a of the metal substrate 1. The intermediate layer 2 may have a multilayer structure. For example, in the order from the metal substrate 1 side toward the oxide superconducting layer 3 side, it may have a diffusion prevention layer, a bed layer, an orientation layer, a cap layer, and the like. These layers are not necessarily provided one by one, and there may be cases where some layers are omitted or the same type of layers are repeatedly laminated two or more times. Note that the intermediate layer 2 is not an essential component in the oxide superconducting wire 10, and when the metal substrate 1 itself has orientation, the intermediate layer 2 may not be formed.

[0021] The diffusion prevention layer has a function of suppressing a part of the components of the metal substrate 1 from diffusing and mixing into the oxide superconducting layer 3 side as impurities. The diffusion prevention layer is composed of, for example, Si3N4, Al2O3, GZO (Gd2Zr2O7), or the like. The thickness of the diffusion prevention layer is, for example, 10 to 400 nm.

[0022] A bed layer may be formed on top of the diffusion prevention layer. The bed layer is provided to reduce the reaction at the interface between the metal substrate 1 and the oxide superconducting layer 3 and to improve the orientation of the layer formed on top of the bed layer. Examples of materials for the bed layer include Y2O3, Er2O3, CeO2, Dy2O3, Eu2O3, Ho2O3, La2O3, etc. The thickness of the bed layer is, for example, 10 to 100 nm.

[0023] The orientation layer is formed from a biaxially oriented material to control the crystal orientation of the cap layer formed on top of the orientation layer. Examples of materials for the orientation layer include metal oxides such as Gd2Zr2O7, MgO, ZrO2-Y2O3(YSZ), SrTiO3, CeO2, Y2O3, Al2O3, Gd2O3, Zr2O3, Ho2O3, and Nd2O3. The orientation layer is preferably formed by the IBAD (Ion-Beam-Assisted Deposition) method.

[0024] The cap layer is formed on the surface of the orientation layer and consists of a material that allows the crystal grains to self-orient in the in-plane direction. Examples of cap layer materials include CeO2, Y2O3, Al2O3, Gd2O3, ZrO2, YSZ, Ho2O3, Nd2O3, and LaMnO3. The thickness of the cap layer can range from 50 to 5000 nm.

[0025] The oxide superconducting layer 3 is composed of an oxide superconductor. The oxide superconductor is not particularly limited, but for example, one with the general formula REBa2Cu3O XAn example is the RE-Ba-Cu-O oxide superconductor (REBCO oxide superconductor) represented by (RE123). The rare earth element RE can be one or more of the following: Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu. Among these, one of Y, Gd, Eu, Sm, or a combination of two or more of these elements is preferred. In the general formula of RE123, X is 7-x (oxygen deficiency x: approximately 0 to 1). The thickness of the oxide superconducting layer 3 is, for example, in the range of 0.5 to 5 μm. It is preferable that the thickness of the oxide superconducting layer 3 is uniform in the longitudinal direction. The oxide superconducting layer 3 is formed on the main surface 2a of the intermediate layer 2 (the surface opposite to the metal substrate 1 side).

[0026] The protective layer 4 has functions such as bypassing overcurrents generated during an accident and suppressing chemical reactions between the oxide superconducting layer 3 and the layer provided on top of the protective layer 4. Examples of materials for the protective layer 4 include silver (Ag), copper (Cu), gold (Au), gold-silver alloys, other silver alloys, copper alloys, and gold alloys. The protective layer 4 covers at least the main surface 3a of the oxide superconducting layer 3 (the surface opposite to the intermediate layer 2). The thickness of the protective layer 4 is not particularly limited, but is, for example, in the range of 1 to 30 μm.

[0027] The superconducting laminate 5 has a first main surface 5a, two side surfaces 5b, 5b, and a second main surface 5c. The first main surface 5a is the main surface 4a of the protective layer 4. The first main surface 5a is the side of the superconducting laminate 5 on which the oxide superconducting layer 3 is provided. The side surfaces 5b are the side surfaces of the metal substrate 1, the intermediate layer 2, the oxide superconducting layer 3, and the protective layer 4. The second main surface 5c is the surface opposite to the first main surface 5a. The second main surface 5c is the second surface 1b of the metal substrate 1. The second main surface 5c is the side of the superconducting laminate 5 on which the metal substrate 1 is provided.

[0028] The stabilization section 6 comprises a first stabilization layer 7 and a second stabilization layer 8. The stabilization section 6 functions as a bypass section that commutates the overcurrent generated when the oxide superconducting layer 3 transitions to a normal conducting state. The thermal expansion coefficient of the stabilization section 6 is greater than that of the metal substrate 1. For example, the thermal expansion coefficient of Hastelloy®, used as a constituent material of the metal substrate 1, is 10.9 × 10⁻⁶. -6 The temperature is / ℃, and the thermal expansion coefficient of copper, which is a component material of the stabilization part 6, is 16.7 × 10⁻⁶. -6 It is / ℃.

[0029] The first stabilization layer 7 covers the first main surface 5a, the side surfaces 5b, 5b, and the second main surface 5c of the superconducting laminate 5. The first stabilization layer 7 is integrally formed surrounding the superconducting laminate 5. The first stabilization layer 7 is formed from the first main surface 5a to the second main surface 5c. Examples of materials that can constitute the first stabilizing layer 7 include copper, copper alloys (e.g., Cu-Zn alloy, Cu-Ni alloy, etc.), aluminum, aluminum alloys, and silver. The thickness of the first stabilizing layer 7 is, for example, in the range of 10 to 500 μm. The first stabilizing layer 7 can be formed, for example, by plating (e.g., electroplating).

[0030] The first stabilization layer 7 has an upper portion 7A and a lower portion 7B. The upper portion 7A is the portion of the first stabilization layer 7 that faces the first main surface 5a. The upper portion 7A is the first portion 6A of the stabilization part 6 (the portion of the stabilization part 6 that faces the first main surface 5a). The thickness of the upper portion 7A (first portion 6A) is denoted as T1. The lower portion 7B is the portion of the first stabilization layer 7 that faces the second main surface 5c. The superconducting laminate 5 and the first stabilizing layer 7 constitute the superconducting wire body 11.

[0031] The second stabilization layer 8 is composed of a metal tape. Examples of metals that make up the metal tape include copper, copper alloys (e.g., Cu-Zn alloy, Cu-Ni alloy, etc.), aluminum, aluminum alloys, and silver. The second stabilization layer 8 is preferably a copper tape.

[0032] The following are examples of the thermal expansion coefficients of the metals listed as constituent materials for the first stabilization layer 7 and the second stabilization layer 8. The thermal expansion coefficient of Cu-Zn alloy is 19.1 × 10⁻⁶. -6The temperature is / ℃, and the thermal expansion coefficient of Cu-Ni alloy is 13.8 × 10⁻⁶. -6 The temperature is / ℃, and the thermal expansion coefficient of aluminum is 23.1 × 10⁻⁶. -6 The thermal expansion coefficient is 22.5 × 10⁻⁶ / °C, and Al-6061, an example of an aluminum alloy, has a thermal expansion coefficient of 22.5 × 10⁻⁶. -6 The temperature is / °C, and the thermal expansion coefficient of silver is 18.5 × 10⁻⁶. -6 The values ​​are given as / °C. These thermal expansion coefficients are for room temperature (293K).

[0033] The second stabilizing layer 8 is joined to the lower surface (outer surface of the lower portion 7B) of the first stabilizing layer 7 by a bonding material 9. Examples of materials that make up the bonding material 9 include metals such as solder, Sn, Sn alloys, In (indium), and In alloys. Examples of solder alloys include Sn-Pb, Pb-Sn-Sb, Sn-Pb-Bi, Bi-Sn, Sn-Cu, Sn-Pb-Cu, and Sn-Ag alloys.

[0034] The portion of the stabilization section 6 facing the second main surface 5c is called the second section 6B. The second section 6B comprises the lower portion 7B of the first stabilization layer 7, the bonding material 9, and the second stabilization layer 8. The thickness of the second section 6B is called T2. The thickness T2 is the sum of the thickness of the lower portion 7B, the thickness of the bonding material 9, and the thickness of the second stabilization layer 8.

[0035] The thickness T2 of the second section 6B is greater than the thickness T1 of the first section 6A (upper section 7A). Because the thickness T2 is greater than the thickness T1, the shear stress generated by the contraction of the stabilization section 6 due to temperature changes is less likely to act on the oxide superconducting layer 3. For example, when cooling, the stabilization section 6 contracts and deforms, but because the first section 6A is thinner than the second section 6B, the shear stress is less likely to act on the oxide superconducting layer 3.

[0036] The difference (T2-T1) between the thickness T2 of the second portion 6B and the thickness T1 of the upper portion 7A (first portion 6A) is preferably greater than the thickness T3 of the metal substrate 1. When this difference (T2-T1) is greater than the thickness T3, the shear stress generated by the contraction of the stabilization portion 6 due to temperature changes is less likely to act on the oxide superconducting layer 3.

[0037] Figure 2 is a schematic diagram of a superconducting coil 20. As shown in Figure 2, the superconducting coil 20 is formed from oxide superconducting wire 10. The superconducting coil 20 is a multilayer wound coil in which the oxide superconducting wire 10 is stacked in the thickness direction and wound multiple times. The oxide superconducting wire 10 is wound around a winding axis C. The superconducting coil 20 is formed in an annular shape and is also called a pancake coil. The direction around the winding axis C, as viewed from the winding axis C, is called the circumferential direction of the superconducting coil 20. The direction perpendicular to the winding axis C is called the radial direction of the superconducting coil 20. Along the radial direction, the direction approaching the winding axis C is called the radially inward direction, and the direction away from the winding axis C is called the radially outward direction.

[0038] It is desirable that the oxide superconducting wire 10 is wound around the winding axis C such that the metal substrate 1 faces radially outward and the oxide superconducting layer 3 faces radially inward. In other words, it is desirable that the oxide superconducting wire 10 is wound around the winding axis C such that the oxide superconducting layer 3 is located radially inward of the metal substrate 1. By winding the oxide superconducting wire 10 so that the oxide superconducting layer 3 is located radially inward of the metal substrate 1, the oxide superconducting layer 3 is pressed against the metal substrate 1 by the Lorentz force acting radially on the superconducting coil 20. Therefore, it is possible to suppress the deterioration of superconducting properties caused by the oxide superconducting layer 3 being peeled away from the metal substrate 1.

[0039] The superconducting coil 20 may have a structure in which insulating tape is wrapped around an oxide superconducting wire 10. The superconducting coil 20 may be impregnated with a resin such as epoxy resin.

[0040] [Effects of the oxide superconducting wire of the first embodiment] In the oxide superconducting wire 10, the thickness T2 of the second portion 6B of the stabilizing portion 6 is greater than the thickness T1 of the first portion 6A (upper portion 7A). When the oxide superconducting wire 10 is exposed to temperature changes, the stabilizing portion 6 shrinks. Since the thickness T2 is greater than the thickness T1, i.e., the thickness T1 is less than the thickness T2, the shear force generated by the shrinkage of the first portion 6A is smaller than the shear force generated by the shrinkage of the second portion 6B. Since the oxide superconducting layer 3 is formed closer to the first portion 6A than to the second portion 6B, the shear stress generated by the shrinkage of the stabilizing portion 6 is less likely to act on the oxide superconducting layer 3. Therefore, damage to the oxide superconducting layer 3 can be suppressed. Thus, the deterioration of the superconducting properties of the oxide superconducting wire 10 can be suppressed.

[0041] For comparison, consider an oxide superconducting wire in which the second stabilization layer 8 is bonded to the outer surface of the upper portion 7A (the upper surface of the first stabilization layer 7) rather than the outer surface of the lower portion 7B (the lower surface of the first stabilization layer 7). In this oxide superconducting wire, the first portion of the stabilization is thicker than the second portion. In this oxide superconducting wire, shear stress is more likely to act on the oxide superconducting layer 3 due to the shrinkage of the second stabilization layer 8 caused by temperature changes. The shear stress tends to increase as the thickness of the second stabilization layer 8 increases.

[0042] [Oxide superconducting wire] (Second embodiment) Figure 3 is a cross-sectional view of the oxide superconducting wire 110 of the second embodiment. Components common to the first embodiment are denoted by the same reference numerals and their descriptions are omitted.

[0043] As shown in Figure 3, the oxide superconducting wire 110 comprises a superconducting laminate 5 and a stabilizing section 106. The oxide superconducting wire 110 is a specific example of a "superconducting wire".

[0044] The stabilization layer 106 is a layer integrally formed covering the superconducting laminate 5. The stabilization layer 106 covers the first main surface 5a, the side surfaces 5b, 5b and the second main surface 5c of the superconducting laminate 5. The stabilization layer 106 is formed surrounding the superconducting laminate 5. The stabilization layer 106 is formed from the first main surface 5a to the second main surface 5c. The thermal expansion coefficient of the stabilization part 106 is greater than that of the metal substrate 1. Examples of materials that can be used to construct the stabilization part 106 include copper, copper alloys (e.g., Cu-Zn alloy, Cu-Ni alloy, etc.), aluminum, aluminum alloys, and silver. The stabilization part 106 can be formed, for example, by plating (e.g., electroplating).

[0045] The portion of the stabilizing part 106 facing the first main surface 5a is called the first portion 106A. The thickness of the first portion 106A is called T11. The portion of the stabilizing part 106 facing the second main surface 5c is called the second portion 106B. The thickness of the second portion 106B is called T12.

[0046] The thickness T12 of the second part 106B is greater than the thickness T11 of the first part 106A. Because the thickness T12 is greater than the thickness T11, the shear stress generated by the contraction of the stabilization part 106 due to temperature changes is less likely to act on the oxide superconducting layer 3. For example, when cooling, the stabilization part 106 contracts and deforms, but since the first part 106A is thinner than the second part 106B, the shear stress is less likely to act on the oxide superconducting layer 3.

[0047] The difference (T12-T11) between the thickness T12 of the second portion 106B and the thickness T11 of the first portion 106A is preferably greater than the thickness T3 of the metal substrate 1. When this difference (T12-T11) is greater than the thickness T3, the shear stress generated by the contraction of the stabilization portion 106 due to temperature changes is less likely to act on the oxide superconducting layer 3.

[0048] [Effects of the oxide superconducting wire of the second embodiment] In the oxide superconducting wire 110, the thickness T12 of the second portion 106B of the stabilizing portion 106 is greater than the thickness T11 of the first portion 106A. When the oxide superconducting wire 110 is exposed to temperature changes, the stabilizing portion 106 shrinks. Since the thickness T12 is greater than the thickness T11, i.e., the thickness T11 is less than the thickness T12, the shear force generated by the shrinkage of the first portion 106A is smaller than the shear force generated by the shrinkage of the second portion 106B. Since the oxide superconducting layer 3 is formed closer to the first portion 106A than to the second portion 106B, the shear stress generated by the shrinkage of the stabilizing portion 106 is less likely to act on the oxide superconducting layer 3. Therefore, damage to the oxide superconducting layer 3 can be suppressed. Thus, the deterioration of the superconducting properties of the oxide superconducting wire 110 can be suppressed.

[0049] Although the present invention has been described above based on preferred embodiments, the present invention is not limited to the embodiments described above, and various modifications are possible without departing from the spirit of the invention. For example, in the oxide superconducting wire 10 shown in Figure 1, the second stabilizing layer 8 is joined to the first stabilizing layer 7 by a bonding material 9, but the second stabilizing layer 8 may be joined directly to the first stabilizing layer 7 without the bonding material 9. In this case, the second stabilizing layer 8 is joined to the first stabilizing layer 7 by, for example, ultrasonic bonding or diffusion bonding.

[0050] The structure of the superconducting laminate is not limited to the structure shown in Figure 1. The superconducting laminate does not need to have a protective layer. The superconducting laminate may include layers other than a metal substrate, an intermediate layer, an oxide superconducting layer, and a protective layer.

[0051] Figure 4 is a cross-sectional view of an oxide superconducting wire 10 of a modified example of the first embodiment. As shown in Figure 4, in this modified example, an unoriented region (non-superconducting region) 32 is formed in the oxide superconducting layer 3. That is, the oxide superconducting layer 3 has an oriented region (superconducting region) 31 and an unoriented region 32. For example, the unoriented region 32 may be formed by forming grooves in a metal substrate 1 or an intermediate layer 2 and providing the oxide superconducting layer 3 on these grooves. The unoriented region 32 extends in the longitudinal direction of the oxide superconducting layer 3. Multiple unoriented regions 32 are arranged side by side in the width direction X. The unoriented region 32 does not have superconducting properties because its orientation is disrupted. Therefore, when in use, current is less likely to flow through the unoriented region 32, and the oxide superconducting layer 3 is substantially divided in the width direction. When the oxide superconducting layer 3 is divided in the width direction by the unoriented region 32, the oxide superconducting layer 3 is thinned (multifilamentized). Therefore, the shielding current and magnetization loss of the oxide superconducting wire 10 can be reduced, and the deterioration of the characteristics of the superconducting coil 20 can be suppressed. In the oxide superconducting wire 10, where the oxide superconducting layer 3 is thinned, a coupling current may flow between adjacent oriented regions 31 separated by a non-oriented region 32, via the stabilizing portion 6 (first portion 6A). This coupling current may degrade the characteristics of the superconducting coil 20. However, because the first portion 6A of the stabilizing portion 6 is thinner than the second portion 6B, the coupling current is less likely to flow between the oriented regions 31 compared to the case where the first portion 6A is thicker than the second portion 6B. Therefore, the degradation of the characteristics of the superconducting coil 20 due to the coupling current can be suppressed.

[0052] Furthermore, similarly to the above, in the oxide superconducting wire 110 of the second embodiment, a non-oriented region 32 may be formed in the oxide superconducting layer 3. That is, in the oxide superconducting wire 110, the oxide superconducting layer 3 may have an oriented region 31 and a non-oriented region 32. In this case as well, since the oxide superconducting layer 3 is thinned (multifilamentized) by the non-oriented region 32, the shielding current and magnetization loss of the oxide superconducting wire 10 can be reduced, and the deterioration of the characteristics of the superconducting coil 20 can be suppressed. In addition, since the first portion 106A of the stabilization portion 106 is thinner than the second portion 106B, coupling current is less likely to flow between the oriented regions 31 compared to the case where the first portion 106A is thicker than the second portion 106B. Therefore, the deterioration of the characteristics of the superconducting coil 20 due to coupling current can be suppressed. [Examples]

[0053] The present invention will be specifically described below with reference to examples.

[0054] (Examples 1-3) A sample of the oxide superconducting wire 10 shown in Figure 1 was prepared as follows. An intermediate layer 2 was formed on one side of a tape-shaped metal substrate 1 made of Hastelloy (registered trademark). The intermediate layer 2 has a structure in which a diffusion prevention layer, a bed layer, an orientation layer, and a cap layer are laminated in this order. An oxide superconducting layer 3 made of GdBCO was formed on the intermediate layer 2. A protective layer 4 made of Ag was formed on the oxide superconducting layer 3. This obtained a superconducting laminate 5. A first stabilizing layer 7 made of copper was formed on the outer surface of the superconducting laminate 5 by electroplating to obtain a superconducting wire body 11 with a width of 4 mm. A second stabilizing layer 8, which is a copper tape, was bonded to the lower surface (outer surface of the lower portion 7B) of the first stabilizing layer 7 using solder as a bonding material 9. This formed a stabilizing portion 6.

[0055] A sample of oxide superconducting wire 10 was placed in liquid nitrogen, and the critical current (Ic) was measured. A sample of the superconducting wire (i.e., the superconducting laminate 5) before the stabilization section 6 was formed was prepared, and the critical current (Ic0) was measured by placing this sample in liquid nitrogen. If the ratio (Ic / Ic0) of the critical current (Ic) of the oxide superconducting wire 10 to the critical current (Ic0) of the superconducting laminate 5 was 0.95 or higher, it was determined that the superconducting properties had not deteriorated. If Ic / Ic0 was less than 0.95, it was determined that the superconducting properties had deteriorated. If the superconducting properties had not deteriorated, it was judged as "pass". If the superconducting properties had deteriorated, it was judged as "fail". The results are shown in Table 1.

[0056] (Example 4) A sample of the oxide superconducting wire 110 shown in Figure 3 was prepared as follows. A stabilizing portion 106 made of copper was formed on the outer surface of the superconducting laminate 5, which was prepared in the same manner as in Examples 1 to 3, by electroplating, thereby obtaining an oxide superconducting wire 110.

[0057] For samples of oxide superconducting wire 110, the presence or absence of a decrease in superconductivity was determined in the same manner as in Examples 1 to 3. The results are shown in Table 1.

[0058] (Comparative Examples 1 and 2) A sample of oxide superconducting wire was prepared in accordance with Example 1, except that the second stabilizing layer 8 was bonded to the outer surface of the upper portion 7A of the first stabilizing layer 7 (the upper surface of the first stabilizing layer 7). The presence or absence of a decrease in superconductivity was determined for this sample in the same manner as in Examples 1 to 3. The results are shown in Table 1.

[0059] (Comparative Example 3) A sample of oxide superconducting wire was prepared in accordance with Example 4, except that the first part of the stabilization section was thicker than the second part. The presence or absence of a decrease in superconductivity was determined for this sample in the same manner as in Examples 1 to 3. The results are shown in Table 1.

[0060] (Reference example 1) A sample of oxide superconducting wire was prepared in the same manner as in Comparative Example 1, except that the second stabilizing layer 8 was relatively thin. The presence or absence of a decrease in superconducting properties was determined for this sample in the same manner as in Examples 1 to 3. The results are shown in Table 1.

[0061] [Table 1]

[0062] As shown in Table 1, the decrease in superconductivity was suppressed in Examples 1 to 4. In contrast, a decrease in superconductivity was observed in Comparative Examples 1 to 3. In reference example 1, no decrease in superconductivity was observed. This is thought to be because the first portion is thin. [Explanation of symbols]

[0063] 1...metal substrate, 3...oxide superconducting layer, 4...protective layer, 5...superconducting laminate, 5a...first main surface, 5c...second main surface, 6,106...stabilization section, 6A,106A...first section, 6B,106B...second section, 7...first stabilization layer, 7B...lower section (section facing the second main surface), 8...second stabilization layer, 10,110...oxide superconducting wire (superconducting wire), 20...superconducting coil, 32...non-oriented region, T1,T11...thickness of the first section, T2,T12...thickness of the second section.

Claims

1. A superconducting laminate having a metal substrate and an oxide superconducting layer, A stabilizing portion is formed covering the superconducting laminate and has a greater coefficient of thermal expansion than the metal substrate, Equipped with, The superconducting laminate has a first main surface which is the side on which the oxide superconducting layer is provided, and a second main surface which is the side on which the metal substrate is provided. The stabilizing portion has a first portion facing the first main surface and a second portion facing the second main surface. The thickness of the second part is greater than the thickness of the first part. The difference between the thickness of the first part and the thickness of the second part is greater than the thickness of the metal substrate. The stabilization unit is A first stabilizing layer surrounding the superconducting laminate, A second stabilizing layer formed of a metal tape and bonded to the portion of the first stabilizing layer facing the second main surface, Equipped with, Between the portion of the first stabilizing layer and the second stabilizing layer, a bonding material is provided to bond the second stabilizing layer to the portion of the first stabilizing layer. The second part comprises the portion of the first stabilizing layer, the bonding material, and the second stabilizing layer. Superconducting wire.

2. The superconducting wire according to claim 1, wherein a non-oriented region extending in the longitudinal direction of the oxide superconducting layer is formed in the oxide superconducting layer.

3. The superconducting wire material described in claim 1, A superconducting coil in which the superconducting wire is wound such that the first portion is located radially inward from the second portion.

Images