Superconducting device, superconducting electromagnet, and method for producing superconducting device

Abstract

To improve productivity of a superconducting device.SOLUTION: A superconducting device 10 comprises: a substrate 11; and a superconducting layer 12 formed on the substrate 11, the superconducting layer 12 containing a perovskite-type copper oxide including RE, Ba, Cu, and O (RE being a rare earth element). The superconducting layer 12 includes a perovskite-type copper oxide having part of RE substituted with Ca, and nanorods or nanoparticles.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to superconducting devices, superconducting electromagnets, and methods for manufacturing superconducting devices. [Background technology]

[0002] Superconducting wires are being developed for application in a wide range of fields, such as coils for superconducting electromagnets. The critical current density (Jc), which is the maximum value of superconducting current that can flow in the superconductor without generating voltage, is extremely important for the performance of superconducting wires, and improvements in Jc characteristics are being sought.

[0003] Among superconductors, YBa2Cu3O 7ーy (YBCO) has a high Tc of 92K and excellent Jc characteristics, making it a promising material for superconducting wires. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] U.S. Patent Publication No. 2023-301202 Summary of the Invention [Problem to be solved by the invention]

[0005] Although the Jc of YBCO single crystals is high, it decreases exponentially depending on the grain boundary tilt angle, and the Jc of YBCO with a grain boundary tilt angle of 5.6° is about 1 / 20 of the Jc of YBCO with a grain boundary tilt angle of 2.1°. Therefore, in order to achieve high Jc characteristics, it is necessary to suppress the effect of grain boundaries with large tilt angles.

[0006] Research is underway to reduce the effects of grain boundaries by improving the orientation of YBCO crystal grains. However, this requires stricter process conditions, which poses challenges to productivity, such as increased manufacturing costs and reduced yields, in order to achieve mass production.

[0007] The present disclosure has been made in view of these problems, and its purpose is to improve the productivity of superconducting devices. [Means for solving the problem]

[0008] In order to solve the above problems, a superconducting device according to an embodiment of the present disclosure includes a substrate and a superconductor layer formed on the substrate and including a perovskite copper oxide (RE is a rare earth element) containing RE, Ba, Cu, and O. The superconductor layer includes a perovskite copper oxide in which part of the RE is substituted with Ca, and nanorods or nanoparticles.

[0009] Another aspect of the present disclosure is a superconducting electromagnet, which comprises the above-described superconducting device wound in a coil.

[0010] Yet another aspect of the present disclosure is a method for manufacturing a superconducting device, comprising forming a superconductor layer on a substrate, the superconductor layer including a perovskite-type copper oxide (RE is a rare earth element) containing RE, Ba, Cu, and O. The superconductor layer includes a perovskite-type copper oxide in which some of the RE is substituted with Ca, and nanorods or nanoparticles. [Effects of the Invention]

[0011] According to the present disclosure, productivity of superconducting devices can be improved. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a diagram schematically illustrating a structure of a superconducting device according to an embodiment of the present disclosure. [Figure 2] 1 is a flowchart illustrating a procedure for a method for manufacturing a superconducting device according to an embodiment of the present disclosure. [Figure 3] 10 is a flowchart illustrating the steps of another example of a method for manufacturing a superconducting device according to an embodiment of the present disclosure. [Figure 4] FIG. 10 is a diagram showing the measurement results of Jc for a sample of a comparative example. [Figure 5]FIG. 10 is a diagram showing the measurement results of Jc for a sample of a comparative example. [Figure 6] FIG. 10 is a diagram showing the measurement results of Jc for a sample of a comparative example and a sample of an example. [Figure 7] FIG. 7 is an enlarged view of FIG. 6. DETAILED DESCRIPTION OF THE INVENTION

[0013] 1 schematically illustrates the structure of a superconducting device 10 according to an embodiment of the present disclosure. The superconducting device 10 includes a substrate 11 and a superconductor layer 12 formed on the substrate 11. The superconductor layer 12 includes a perovskite copper oxide containing rare earth elements, Ba, Cu, and O. The superconductor layer 12 includes a perovskite copper oxide in which some of the rare earth elements are substituted with Ca, and nanorods or nanoparticles.

[0014] YBa2Cu3O 7ーy REBa2Cu3O, represented by (YBCO) 7ーy In a (REBCO)-based superconductor (RE is a rare earth element), when a portion of the rare earth element RE in the REBCO layer is replaced with Ca, holes are doped, thereby improving the Jc characteristics. Furthermore, in a REBCO-based superconductor, when nanorods such as BaMO3 (M is Hf, Zr, or Sn) are introduced into the REBCO layer, the nanorods function as pinning centers, improving the Jc characteristics in a magnetic field. Therefore, the superconducting device 10 of this embodiment can suppress the influence of grain boundaries and improve the Jc characteristics in a magnetic field. It is thought that doping with Ca improves the Jc characteristics mainly at the crystal grain boundaries, and introducing nanorods or nanoparticles improves the Jc characteristics mainly within the crystal grains.

[0015] As will be shown in the examples described later, experiments by the present inventors have revealed that by alternately stacking a first layer 13 containing a superconductor in which part of the RE of REBCO is substituted with Ca and a second layer 14 in which nanorods of BaMO3 (M is Hf, Zr, Sn) are introduced into REBCO, the Jc characteristics in a magnetic field can be further improved compared to a superconducting device in which only part of the RE of REBCO is substituted with Ca, a superconducting device in which only nanorods of BaMO3 (M is Hf, Zr, Sn) are introduced into REBCO, or a superconducting device in which a superconductor in which part of the RE is substituted with Ca and nanorods of BaMO3 (M is Hf, Zr, Sn) are introduced into the same layer.

[0016] Therefore, in the example shown in FIG. 1, the superconductor layer 12 has a multilayer structure including a first layer 13 containing perovskite copper oxide in which some of the RE has been substituted with Ca, and a second layer 14 containing perovskite copper oxide in which nanorods or nanoparticles have been introduced.

[0017] According to this embodiment, the influence of grain boundaries can be suppressed and the Jc characteristics of the superconducting device 10 in a magnetic field can be further improved by an approach different from that of conventional techniques that improve the Jc characteristics by improving the orientation of the substrate or superconductor layer, thereby relaxing the conditions related to the orientation of the substrate or superconductor layer when manufacturing a superconducting device. This makes it possible to improve the yield and reduce the manufacturing cost, thereby improving the productivity of superconducting devices. Ultimately, it becomes possible to realize mass production of superconducting devices for applications such as wire for superconducting electromagnets.

[0018] The substrate 11 may be any known substrate usable as a substrate for a superconducting device. The substrate 11 may be any substrate practically used as a superconducting wire. The substrate 11 may be an oriented oxide thin film laminated on a metal tape. The substrate 11 may be manufactured by an ion-beam-assisted deposition (IBAD) method, a rolling-assisted biaxially textured substrate (RABiTS) method, or the like. In the superconducting device 10 of this embodiment, the conditions regarding the orientation of the substrate can be relaxed, so the grain boundary tilt angle of the substrate 11 may be, for example, 5.6° or less. The grain boundary tilt angle of the substrate 11 may be 10° or less, 9° or less, 8° or less, 7° or less, 6° or less, 5° or less, 4° or less, or 3° or less. This can improve the yield of the substrate. It can also reduce the manufacturing cost of the superconducting device.

[0019] The superconductor constituting the superconductor layer 12 is REBa2Cu3O 7ーy RE may be a rare earth element, particularly Y, La, Nd, Eu, Sm, Gd, Dy, Er, or Yb. By using such a high-temperature superconductor, it is possible to provide a superconducting device that can operate at liquid nitrogen temperature and has excellent Jc characteristics.

[0020] The Ca doping amount in first layer 13 is preferably about 5%. The Ca doping amount in first layer 13 may be 1% or more, 2% or more, 3% or more, 4% or more, 5% or more, 6% or more, 7% or more, 8% or more, 9% or more, or 10% or more. The Ca doping amount in first layer 13 may be 10% or less, 9% or less, 8% or less, 7% or less, 6% or less, 5% or less, 4% or less, 3% or less, 2% or less, or 1% or less.

[0021] The nanorods or nanoparticles contained in the second layer 14 may include at least one of BaMO3 (where M is Hf, Zr, Sn) and Ba2RENbO6 (where RE is Nd, Sm, Gd, Yb, Lu, Y).

[0022] The content of nanorods or nanoparticles in second layer 14 is preferably about 3 wt % based on the total weight of the superconductor in second layer 14. The content of nanorods or nanoparticles in second layer 14 may be 0.5 wt % or more, 1 wt % or more, 1.5 wt % or more, 2 wt % or more, 2.5 wt % or more, 3 wt % or more, 3.5 wt % or more, 4 wt % or more, 4.5 wt % or more, or 5 wt % or more based on the total weight of the superconductor in second layer 14. The content of nanorods or nanoparticles in second layer 14 may be 5 wt % or less, 4.5 wt % or less, 4 wt % or less, 3.5 wt % or less, 3 wt % or less, 2.5 wt % or less, 2 wt % or less, 1.5 wt % or less, or 1 wt % or less based on the total weight of the superconductor in second layer 14.

[0023] Two or more first layers 13 and two or more second layers 14 may be alternately stacked. A total of three or more, four or more, five or more, six or more, seven or more, eight or more, nine or more, or ten or more first layers 13 and two or more second layers 14 may be stacked.

[0024] The thickness of first layer 13 is preferably about 30 to 40 nm. The thickness of first layer 13 may be 10 nm or more, 15 nm or more, 20 nm or more, 25 nm or more, 30 nm or more, 35 nm or more, or 40 nm or more. The thickness of first layer 13 may be 60 nm or less, 55 nm or less, 50 nm or less, 45 nm or less, 40 nm or less, 35 nm or less, or 30 nm or less.

[0025] When the superconductor layer 12 includes a plurality of first layers 13, the film thickness of each of the first layers 13 may be the same or different. The Ca content of each of the first layers 13 may be the same or different.

[0026] The thickness of second layer 14 is preferably about 30 to 40 nm. The thickness of second layer 14 may be 10 nm or more, 15 nm or more, 20 nm or more, 25 nm or more, 30 nm or more, 35 nm or more, or 40 nm or more. The thickness of second layer 14 may be 60 nm or less, 55 nm or less, 50 nm or less, 45 nm or less, 40 nm or less, 35 nm or less, or 30 nm or less.

[0027] When the superconductor layer 12 includes multiple second layers 14, the second layers 14 may all have the same thickness or may be different from each other. The content of nanorods or nanoparticles contained in the second layers 14 may all be the same or may be different from each other.

[0028] The superconducting device 10 may include a first region having a multilayer structure and a second region not having a multilayer structure. In the first region, where the grain boundary tilt angle of the substrate 11 or the superconductor layer 12 is large, the Jc characteristics are poor as they are. Therefore, the superconductor layer 12 may be formed with a multilayer structure including the first layer 13 and the second layer 14. In the second region, where the grain boundary tilt angle is small, the Jc characteristics are good even without the introduction of Ca or nanorods. Therefore, the superconductor layer 12 may be formed of REBCO alone. This improves the Jc characteristics of the entire superconducting device. In particular, for superconducting wires on the order of kilometers, it is difficult to keep the grain boundary tilt angle small throughout the substrate. If a region with a large grain boundary tilt angle exists, that region may become a bottleneck. The superconducting device of this embodiment can realize a superconducting wire on the order of kilometers with excellent Jc characteristics throughout.

[0029] The superconductor layer 12 may contain nanorods and Ca substituting for RE in REBCO in the same layer, which can simplify the film formation process and reduce the manufacturing cost.

[0030] 2 is a flowchart showing the steps of a method for manufacturing a superconducting device according to an embodiment of the present disclosure. First, a substrate 11 is prepared (S10). Next, a Ca-doped first layer 13 is formed (S12), and a nanorod-doped second layer 14 is formed (S14). Steps S12 and S14 are repeated until a predetermined number of first layers 13 and second layers 14 are stacked (N in S16). When a predetermined number of first layers 13 and second layers 14 are stacked (Y in S16), the manufacturing of the superconducting device 10 is completed. Further steps such as bridging and metal coating required for the superconducting device 10 may be performed.

[0031] The first layer 13 and the second layer 14 may be formed by pulsed laser deposition (PLD), metal organic chemical vapor deposition (MOCVD), or the like.

[0032] 3 is a flowchart showing the steps of another example of a method for manufacturing a superconducting device according to an embodiment of the present disclosure. First, a substrate 11 is fabricated (S20). Next, the surface state of the fabricated substrate 11 is acquired for each predetermined area (S22). The surface state of the substrate 11 may be observed by reflection high energy electron diffraction (RHEED) or the like.

[0033] If the surface condition of the substrate 11 in the target area does not satisfy the conditions necessary to obtain the Jc characteristics required for the superconducting device 10 (N in S24), a first layer 13 and a second layer 14 are stacked to form a superconductor layer 12 in order to improve the Jc characteristics of the superconducting device 10 in the target area (S26). If the surface condition of the substrate 11 in the target area satisfies the conditions (Y in S24), a superconductor layer 12 consisting only of REBCO is formed without introducing Ca or nanorods (S28). Until the formation of the superconductor layer 12 on the entire area of ​​the substrate 11 is completed (N in S30), the process returns to S22, and the acquisition of the surface condition of the substrate 11 and the formation of the superconductor layer 12 are repeated. When the formation of the superconductor layer 12 on the entire area of ​​the substrate 11 is completed (Y in S30), the production of the superconducting device 10 is terminated.

[0034] The condition in S24 may be a condition related to the grain boundary tilt angle of the substrate 11. The condition may be that the grain boundary tilt angle of the substrate 11 is equal to or less than a predetermined value. The predetermined value may be 10°, 9°, 8°, 7°, 6°, 5°, 4°, 3°, 2°, or 1°.

[0035] The superconducting device of the present disclosure can be manufactured by pulsed laser deposition (PLD) using a perovskite-type oxide target in which some of the rare earth elements are substituted with Ca, including nanorod or nanoparticle raw materials, or by metal organic chemical vapor deposition (MOCVD) using organometallic complexes of each element as raw materials.

[0036] The superconducting electromagnet of the present disclosure includes the superconducting device 10 of the present embodiment wound in a coil shape. The superconducting device 10 may be a wire rod. In this case, the substrate 11 may be formed on a flexible metal tape. The substrate 11 may include a biaxially oriented buffer layer.

[0037] [Example] A sample of a superconducting device was fabricated by the manufacturing method according to the embodiment, and the Jc characteristics were measured.

[0038] [Sample preparation] A superconducting device sample was deposited by pulsed laser deposition (PLD). A substrate manufactured by ion-beam-assisted deposition (IBAD) was used. The grain boundary tilt angle Δφ of CeO2 on the top surface of the substrate was 5.6°. The substrate was set inside a chamber, and the oxygen partial pressure was set to 53 Pa and the temperature to 860°C. A KrF excimer laser was used to deposit a film at 110 mJ for 1 minute using a YBCO target with 3 wt% BHO (BaHfO3) added. Next, the target was revolved, and the Y 0.95 Ca 0.05 Ba2Cu3O y Films were formed under the same film formation conditions using a target of YBCO. The targets were prepared by a known, general method. Each of these processes was repeated four times, for a total of eight times. The film thickness was 30-40 nm, and the total film thickness was 300 nm. After bridge processing (width 100 μm, length 1 mm) and silver coating were performed on the film, oxygen annealing was performed at 400°C for two hours (a total of three hours including one hour for heating up). Terminals were attached, and the magnetic field dependence of Jc was measured using a Physical Properties Measurement System (PPMS (registered trademark)). In addition, as comparative examples, samples were formed using substrates with grain boundary tilt angles Δφ of 2.1° and 5.6°, using only YBCO as a target, a sample using only YBCO with 3 wt% BHO added as a target, and a sample using YBCO with 3 wt% BHO added as a target. 0.95 Ca 0.05 Ba2Cu3O y The Jc of the sample formed using only the target was measured.

[0039] [Jc characteristics] Figure 4 shows the Jc measurement results for comparative samples. The solid circular plots show the Jc of a sample in which only YBCO was deposited on a substrate with a grain boundary tilt angle of 2.1°. The solid triangular plots show the Jc of a sample in which only YBCO was deposited on a substrate with a grain boundary tilt angle of 5.6°. The Jc of YBCO with a grain boundary tilt angle of 5.6° is approximately 1 / 20 of the Jc of YBCO with a grain boundary tilt angle of 2.1°.

[0040] FIG. 5 shows the measurement results of Jc for the comparative samples. The solid circular plots show the Jc of the samples in which only YBCO was deposited using a substrate with a grain boundary tilt angle of 2.1°. The solid triangular plots show the Jc of the samples in which only YBCO was deposited using a substrate with a grain boundary tilt angle of 5.6°. These Jc measurement results are the same as those shown in FIG. 4, and in this figure, Jc is between 1 and 10 (MA / cm 2 The solid square plot shows the area where the grain boundary tilt angle is 5.6°. 0.95 Ca 0.05 Ba2Cu3O y This shows the Jc of a sample in which only Y was deposited. By substituting a portion of Y with Ca, Jc is increased.

[0041] Fig. 6 shows the measurement results of Jc for the comparative example sample and the example sample. Fig. 7 shows the results for the samples with Jc of 1 to 10 (MA / cm 2 ) is shown enlarged. The hollow square plot shows the Jc of a sample deposited using a YBCO target with 3 wt% BHO added and a substrate with a grain boundary tilt angle of 2.1°. The hollow triangle plot shows the Jc of a sample deposited using a YBCO target with 3 wt% BHO added and a substrate with a grain boundary tilt angle of 5.6°. In both cases where the grain boundary tilt angle is 2.1° and 5.6°, the introduction of BHO nanorods increases Jc.

[0042] The hollow circular plots represent the YBCO film with 3 wt% BHO added using a substrate with a grain boundary tilt angle of 5.6°. 0.95 Ca 0.05 Ba2Cu3O yThe Jc of the sample formed using the target is shown. When Ca and BHO nanorods are introduced into the same layer, the Jc characteristics are improved or maintained.

[0043] The solid circular plots show the Jc of the example sample, in which the first and second layers were stacked on a substrate with a grain boundary tilt angle of 5.6°. The example sample exhibited a higher Jc than all of the following samples, all with the same grain boundary tilt angle of 5.6°: a sample made of YBCO alone, a sample doped with Ca, a sample with BHO nanorods introduced into YBCO, and a sample with Ca and BHO nanorods introduced into the same YBCO layer. In particular, in a magnetic field around 5 T, the example sample exhibited a high Jc comparable to that of a sample with a grain boundary tilt angle of 2.1° and BHO nanorods introduced.

[0044] The present disclosure has been described above based on examples. These examples are merely illustrative, and it will be understood by those skilled in the art that various modifications are possible in the combination of the components and processing steps, and that such modifications are also within the scope of the present disclosure. [Industrial Applicability]

[0045] The present invention can be used in superconducting devices and methods for manufacturing superconducting devices. [Explanation of symbols]

[0046] 10 superconducting device, 11 substrate, 12 superconductor layer, 13 first layer, 14 second layer.

Claims

1. A substrate; a superconductor layer formed on the substrate and including a perovskite-type copper oxide containing RE, Ba, Cu, and O (RE is a rare earth element); Equipped with The superconductor layer includes the perovskite copper oxide in which part of RE is substituted with Ca, and nanorods or nanoparticles. Superconducting devices.

2. The nanorods or nanoparticles are BaMO ３ (M is Hf, Zr, Sn) or Ba ２ RENbO ６ (RE includes Nd, Sm, Gd, Yb, Lu, Y) 10. The superconducting device of claim 1.

3. The superconductor layer is a first layer containing the perovskite copper oxide in which part of RE is substituted with Ca; a second layer including the perovskite copper oxide having nanorods or nanoparticles introduced therein; Contains 10. The superconducting device of claim 1.

4. The superconductor layer is a first region having a multilayer structure including the first layer and the second layer; a second region not having the multilayer structure; Contains 4. The superconducting device of claim 3.

5. The grain boundary tilt angle of the substrate or the superconductor layer in the first region is larger than the grain boundary tilt angle of the substrate or the superconductor layer in the second region.

5. The superconducting device of claim 4.

6. The superconducting device is a wire.

6. A superconducting device according to any one of claims 1 to 5.

7. The superconducting device according to claim 6 is provided in a coil shape. Superconducting electromagnet.

8. forming a superconductor layer containing perovskite-type copper oxide containing RE, Ba, Cu, and O (RE is a rare earth element) on a substrate; The superconductor layer includes the perovskite copper oxide in which part of RE is substituted with Ca, and nanorods or nanoparticles. Methods for manufacturing superconducting devices.

9. The nanorods or nanoparticles are BaMO ３ (M is Hf, Zr, Sn) or Ba ２ RENbO ６ (RE includes Nd, Sm, Gd, Yb, Lu, Y) The method of claim 8.

10. The step of forming the superconductor layer comprises: forming a first layer containing the perovskite copper oxide in which a portion of RE is substituted with Ca; forming a second layer comprising the perovskite copper oxide having nanorods or nanoparticles introduced therein; Contains 10. The method according to claim 8 or 9.

11. acquiring a surface condition of the substrate; The step of forming the superconductor layer comprises: forming a superconductor layer containing perovskite-type copper oxide containing RE, Ba, Cu, and O (RE is a rare earth element) on the substrate in a region where the surface condition of the substrate is good; laminating the first layer and the second layer alternately in an area of ​​the substrate where the surface condition is poor; Contains The method of claim 10.

12. The region of the substrate in which the surface condition is good is a region of the substrate in which the grain boundary tilt angle is 5.6° or less. The method of claim 11.

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