Oxide superconducting wire material, superconducting coil, and superconductor

Abstract

This oxide superconducting wire rod is provided with: a strip-shaped metal substrate comprising a nickel alloy; an intermediate layer laminated on the metal substrate; and an oxide superconducting layer laminated on the intermediate layer. The average crystal grain size of the metal substrate is 3.08 [mu] m or more and less than or equal to the thickness of the metal substrate.

Description

Technical Field

[0001] The present invention relates to an oxide superconducting wire, a superconducting coil and a superconductor.

[0002] This application claims priority based on Japanese Patent Application No. 2022-172013 filed in Japan on October 27, 2022, and the contents are incorporated herein by reference. Background Art

[0003] Patent Document 1 discloses an oxide superconducting wire including a tape-shaped metal substrate, an intermediate layer stacked on the metal substrate, and an oxide superconducting layer stacked on the intermediate layer.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2020-166983 Summary of the invention

[0007] 1. Technical issues to be resolved

[0008] In the past, when excessive tensile stress was applied to the oxide superconducting wire in the length direction, there was a problem of reduced characteristics of the oxide superconducting wire. Generally, the rigidity of the oxide superconducting layer is higher than that of the metal substrate, and it is not easy to produce elongation deformation. Therefore, when excessive tensile stress was applied to the oxide superconducting wire in the length direction, there was a situation where the oxide superconducting layer could not withstand the elongation deformation of the metal substrate and cracks were generated in the oxide superconducting layer. Since the resistance of the cracked part becomes higher, there is a problem of reduced superconducting characteristics of the oxide superconducting layer.

[0009] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an oxide superconducting wire, a superconducting coil, and a superconductor whose superconducting characteristics are unlikely to be degraded even when tensile stress is applied.

[0010] (II) Technical solution

[0011] In order to solve the above-mentioned technical problems, the oxide superconducting wire of scheme 1 of the present invention comprises a strip-shaped metal substrate made of a nickel alloy, an intermediate layer stacked on the metal substrate, and an oxide superconducting layer stacked on the intermediate layer, wherein the average grain size of the metal substrate is greater than 3.08 μm and less than the thickness of the metal substrate.

[0012] According to the first aspect of the present invention, it is possible to realize an oxide superconducting wire having a high allowable strain amount in LN 2 , that is, an oxide superconducting wire whose superconducting characteristics are not easily degraded even when tensile stress is applied.

[0013] Furthermore, in the second aspect of the present invention, the standard deviation of the crystal grain size of the metal substrate in the oxide superconducting wire of the first aspect is within a range of 2.32 to 14.66 μm.

[0014] According to the second aspect of the present invention, it is possible to realize an oxide superconducting wire having a metal substrate in which recrystallization has hardly progressed and which has high tensile resistance.

[0015] Furthermore, in aspect 3 of the present invention, the average crystal grain size in the oxide superconducting wire of aspect 1 or aspect 2 is an average value of crystal grain sizes in a cross section along the length direction and the thickness direction of the metal substrate.

[0016] Furthermore, in aspect 4 of the present invention, the average crystal grain size in the oxide superconducting wire of any one of aspects 1 to 3 is an average value of crystal grain sizes measured by a reflection EBSD (electron backscatter diffraction) method.

[0017] Furthermore, a superconducting coil according to claim 5 of the present invention is formed by winding the oxide superconducting wire according to any one of claims 1 to 4.

[0018] Furthermore, the superconductor according to claim 6 of the present invention is obtained by assembling a plurality of oxide superconducting wires according to any one of claims 1 to 4.

[0019] (III) Beneficial effects

[0020] According to the above aspects of the present invention, it is possible to provide an oxide superconducting wire, a superconducting coil, and a superconductor in which superconducting characteristics are unlikely to be degraded even when tensile stress is applied. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a cross-sectional view showing an oxide superconducting wire according to an embodiment of the present invention.

[0022] Figure 2 This is a graph showing the relationship between the average crystal grain size of the metal substrate and the allowable strain amount in LN2.

[0023] Figure 3 For use Figure 1 A three-dimensional view of a superconducting coil of an oxide superconducting wire.

[0024] Figure 4A To show the use of Figure 1 Diagram of an oxide superconductor wire.

[0025] Figure 4B To show the use of Figure 1 A diagram of another example of an oxide superconductor.

[0026] Figure 4CTo show the use of Figure 1 A diagram of yet another example of an oxide superconductor. DETAILED DESCRIPTION

[0027] Hereinafter, an oxide superconducting wire according to an embodiment of the present invention will be described with reference to the drawings.

[0028] like Figure 1 As shown, the oxide superconducting wire 10 of the present embodiment includes a metal substrate 11, an intermediate layer 12, an oxide superconducting layer 13, a protective layer 14, and a stabilizing layer 16. Hereinafter, the metal substrate 11, the intermediate layer 12, the oxide superconducting layer 13, and the protective layer 14 are sometimes collectively referred to as a "superconducting laminate 15".

[0029] The metal substrate 11, the intermediate layer 12, the oxide superconducting layer 13 and the protective layer 14 are respectively formed in a strip shape. The metal substrate 11, the intermediate layer 12, the oxide superconducting layer 13 and the protective layer 14 are stacked in sequence in the thickness direction of the metal substrate 11 (the thickness direction of the oxide superconducting wire 10). The stabilizing layer 16 covers the outer periphery of the superconducting laminate 15. The oxide superconducting wire 10 is in a strip shape.

[0030] (Direction definition)

[0031] Here, in the present embodiment, an XYZ rectangular coordinate system is set to illustrate the positional relationship of each structure. The Z-axis direction (not shown) is a direction along the length direction of the oxide superconducting wire 10. The Y-axis direction is a direction orthogonal to the Z-axis direction, and is a direction along the thickness direction of the oxide superconducting wire 10. The Y-axis direction is also the stacking direction of each layer 11 to 14 of the superconducting laminate 15. The X-axis direction is a direction orthogonal to the Z-axis direction and the Y-axis direction, and is a direction along the width direction of the oxide superconducting wire 10. In this specification, the X-axis direction is sometimes referred to as the width direction X, the Y-axis direction is referred to as the thickness direction Y, and the Z-axis direction is referred to as the length direction Z. In addition, the direction from the metal substrate 11 toward the oxide superconducting layer 13 along the thickness direction Y is referred to as the +Y direction or the top. The direction opposite to the +Y direction is referred to as the -Y direction or the bottom. The direction along one side of the width direction X is referred to as the +X direction or the right side. The direction opposite to the +X direction is referred to as the -X direction or the left side.

[0032] A specific example of the metal constituting the metal substrate 11 is a nickel alloy represented by Hastelloy (registered trademark). The thickness of the metal substrate 11 may be appropriately adjusted according to the purpose, and is, for example, in the range of 10 to 1000 μm.

[0033] The intermediate layer 12 is stacked on the metal substrate 11 (the upper surface of the metal substrate 11). The structure of the intermediate layer 12 is not limited to Figure 1For example, the intermediate layer 12 may have a multilayer structure. In this case, the intermediate layer 12 may have a diffusion prevention layer, a bed layer, an orientation layer, and a cap layer in sequence in the direction from the substrate 11 toward the oxide superconducting layer 13. These layers are not limited to being arranged in a manner where each layer is one layer. Sometimes some layers may be omitted, or sometimes more than two layers of the same layer may be repeatedly stacked. The intermediate layer 12 may be a metal oxide. By forming the oxide superconducting layer 13 on the upper surface of the intermediate layer 12 having excellent orientation, an oxide superconducting layer 13 having excellent orientation can be easily obtained.

[0034] The oxide superconducting layer 13 is stacked on the intermediate layer 12 (the upper surface of the intermediate layer 12). The oxide superconducting layer 13 is composed of an oxide superconductor. Examples of the oxide superconductor constituting the oxide superconducting layer 13 include a general formula of RE1Ba2Cu3O y (RE123) and the like represent RE-Ba-Cu-O system oxide superconductor (REBCO system oxide superconductor). As rare earth elements RE, one or more of Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu can be listed. In the general formula of RE123, y is 7-x (oxygen deficiency amount: about 0 to 1). In addition, the ratio of RE:Ba:Cu is not limited to 1:2:3, and can also be an indefinite ratio. The thickness of the oxide superconducting layer 13 is, for example, in the range of 0.5 to 5 μm. The oxide superconducting layer 13 can be formed by a PLD (pulsed laser deposition) film forming method or the like.

[0035] Artificial pinning formed of different materials as artificial crystal defects can be introduced into the oxide superconducting layer 13. As different materials for introducing artificial pinning into the oxide superconducting layer 13, for example, at least one material selected from BaSnO3 (BSO), BaZrO3 (BZO), BaHfO3 (BHO), BaTiO3 (BTO), SnO2, TiO2, ZrO2, LaMnO3, ZnO, etc. can be listed.

[0036] The protective layer 14 is stacked on the oxide superconducting layer 13 (the upper surface of the oxide superconducting layer 13). The protective layer 14 has functions such as diverting the overcurrent generated during a fault, or suppressing the chemical reaction between the oxide superconducting layer 13 and the layer arranged on the protective layer 14. As the material of the protective layer 14, for example, silver (Ag), copper (Cu), gold (Au), alloys of gold and silver, other silver alloys, copper alloys, gold alloys, etc. can be listed. The thickness of the protective layer 14 is, for example, in the range of 1 to 30 μm. The protective layer 14 can be composed of two or more metals or more than two metal layers. The protective layer 14 can be formed by evaporation, sputtering, etc.

[0037] The stabilizing layer 16 is formed so as to extend over the entire periphery of the superconducting laminate 15. In other words, the stabilizing layer 16 covers the upper surface, the lower surface, and a pair of side surfaces of the superconducting laminate 15 at the same time. In addition, in the present embodiment, the "upper surface of the superconducting laminate 15" corresponds to the upper surface of the protective layer 14, the "lower surface of the superconducting laminate 15" corresponds to the lower surface of the metal substrate 11, and the "side surfaces of the superconducting laminate 15" correspond to the side surfaces of each layer 11 to 14. The stabilizing layer 16 has functions such as diverting overcurrent generated during a fault or mechanically reinforcing the oxide superconducting layer 13 and the protective layer 14. The stabilizing layer 16 is, for example, composed of a copper (Cu) plating layer. The thickness of the stabilizing layer 16 is not particularly limited, and is, for example, in the range of 1 to 300 μm.

[0038] Generally, the oxide superconducting layer has higher rigidity than the metal substrate and is not easily deformed by elongation. Therefore, when excessive tensile stress is applied to the oxide superconducting wire in the longitudinal direction, the oxide superconducting layer may not be able to withstand the elongation deformation of the metal substrate and cracks may occur in the oxide superconducting layer. Since the resistance of the cracked portion increases, there is a problem of reduced superconducting properties of the oxide superconducting layer.

[0039] The inventors of the present application have conducted in-depth research on this issue and found that the degradation of superconducting properties when tensile stress is applied can be suppressed by appropriately setting the average grain size of the metal substrate 11. The appropriate value of the average grain size of the metal substrate 11 is described below using specific examples. In addition, the present invention is not limited to the following examples.

[0040] Example

[0041] Oxide superconducting wires of comparative examples 1 to 6 and embodiments 1 to 18 were prepared. These oxide superconducting wires have a metal substrate 11 having a thickness of 30 μm, 50 μm or 75 μm, and the average grain size of the metal substrate 11 in each oxide superconducting wire is different from each other. The thickness and average grain size of the metal substrate 11 of the oxide superconducting wire 10 are shown in Table 1. Among the multiple oxide superconducting wires 10 prepared, the conditions other than the thickness and average grain size of the metal substrate 11 are common as listed below. In addition, the average grain size of the metal substrate 11 can be adjusted by adjusting the conditions when the metal substrate 11 is rolled (temperature, grain size of the substrate before rolling, etc.) or the conditions when the intermediate layer 12 and the oxide superconducting layer 13 are formed (temperature, time, etc.).

[0042] Material of metal substrate 11: Hastelloy

[0043] Width of metal substrate 11: 4 mm

[0044] Material of oxide superconducting layer 13: EuBCO+BHO

[0045] Thickness of oxide superconducting layer 13: 2 μm

[0046] Film formation method of oxide superconducting layer 13: Pulsed laser deposition film formation

[0047] Material of protective layer 14: Ag

[0048] Thickness of protective layer 14: 2 μm

[0049] Film forming method of protective layer 14: Sputtering film forming

[0050] Material of stabilizing layer 16: Cu

[0051] Thickness of stabilization layer 16: 5 μm

[0052] Film forming method of stabilizing layer 16: film forming by plating

[0053] In addition, as the intermediate layer 12, a commonly used intermediate layer is adopted.

[0054] Table 1 is a table summarizing the average grain size of the metal substrate 11 of each oxide superconducting wire of Comparative Examples 1 to 6 and Examples 1 to 18, the standard deviation of the grain size of the metal substrate 11, and the measurement results of the allowable strain amount in LN2 (details will be described later). In Table 1, when the allowable strain amount in LN2 is 0.40% or more, the tensile resistance is judged as "acceptable", and when the allowable strain amount in LN2 is less than 0.40%, the tensile resistance is judged as "unacceptable". Figure 2 Graph showing the relationship between the average crystal grain size of the metal substrate 11 and the allowable strain amount in LN2.

[0055] [Table 1]

[0056]

[0057] The allowable strain in LN2 is a parameter showing the resistance of the oxide superconducting wire to tensile stress. Specifically, the allowable strain in LN2 is defined as the maximum strain among the strains that maintain the characteristics (superconducting characteristics) of the oxide superconducting wire. Here, the strain is a parameter representing the elongation of the oxide superconducting wire, and the natural length of the oxide superconducting wire is set to L0, and the length of the oxide superconducting wire in the elongated state is set to L1, and is defined using the following formula.

[0058] Strain[%]=100×(L1-L0) / L0

[0059] In addition, whether the superconducting characteristics are maintained is determined by the value of the ratio of the critical current value Ic0 when the oxide superconducting wire is in its natural length to the critical current value Ic1 when the oxide superconducting wire is extended (Ic1 / Ic0). If the value of Ic1 / Ic0 is 0.95 or more, it is determined that "the characteristics are maintained", and if the value of Ic1 / Ic0 is less than 0.95, it is determined that "the characteristics are not maintained".

[0060] The average crystal grain size of the metal substrate 11 in the produced oxide superconducting wire was calculated as the average value of the crystal grain sizes measured by the reflection EBSD (electron backscatter diffraction) method. The observation conditions of the sample in the EBSD method are as follows.

[0061] Accelerating voltage: 15 kV

[0062] Irradiation current: 15nA

[0063] Sample tilt angle: 70°

[0064] Sample observation points: any 1 point

[0065] Interval: 150nm / step

[0066] In addition, regarding the sample observation range, it is set to 45×45μm in Comparison Example 1, Comparison Example 2 and Examples 1 to 12 with a substrate thickness of 50μm, set to 25×25μm in Comparison Example 3, Comparison Example 4 and Examples 13 to 15 with a substrate thickness of 30μm, and set to 70×70μm in Comparison Example 5, Comparison Example 6 and Examples 16 to 18 with a substrate thickness of 75μm.

[0067] In addition, when the grain size is measured using the reflection EBSD method, the grain size of the grain obtained when the crystal orientation angle difference is 5° or more and the Σ3 twin grain boundary is used as the grain boundary is used as the grain size. In addition, the area with low reliability of the crystal orientation attribution of the reflection EBSD pattern is excluded, and the area with a reliability parameter CI (Confidence Index) value of 0.1 or more is used. Specifically, when measuring the grain size of the metal substrate 11, a cross-sectional sample along the length and thickness directions of the metal substrate 11 is prepared by mechanical polishing and Ar ion milling, and the cross-sectional sample is observed and measured. The thermal field emission scanning electron microscope (TFE-SEM) JSM-6500F of JEOL Ltd. is used for the observation of the grain size. In addition, the area average grain size weighted by the area ratio of each observed grain in the entire field of view is used as the average grain size.

[0068] The reason why the tensile strength is judged as "acceptable" or "unacceptable" based on whether the allowable strain amount in LN2 is 0.40% or more is as follows.

[0069] Usually, in superconducting coils, etc., tensile stress caused by the electromagnetic force of the superconducting coil is applied to the oxide superconducting wire. It is required that the superconducting characteristics are not damaged even when the tensile stress caused by the electromagnetic force is applied to the oxide superconducting wire. The inventors of the present application have studied oxide superconducting wires whose characteristics deteriorate after coiling and oxide superconducting wires whose characteristics do not deteriorate even after coiling. As a result, it is found that the allowable strain in LN2 of 0.40% is used as the boundary to divide them into those with and without characteristic degradation. Therefore, in this embodiment, whether the tensile resistance is "qualified" or "unqualified" is judged based on whether the allowable strain in LN2 is 0.40% or more.

[0070] like Figure 2 As shown in Table 1, the larger the average grain size of the metal substrate 11, the larger the allowable strain amount in LN2 becomes. In addition, the tensile resistance determination results of Examples 1 to 18 in which the average grain size of the metal substrate 11 is 3.08 μm or more are "qualified", and the tensile resistance determination results of Comparative Examples 1 to 6 in which the average grain size of the metal substrate 11 is less than 3.08 μm are "unqualified". In addition, as shown in Table 1, the standard deviation of the grain size of the metal substrate 11 of Examples 1 to 18 in which the tensile resistance determination results are "qualified" is larger than that of Comparative Examples 1 to 6 in which the tensile resistance determination results are "unqualified". Next, the above results are studied.

[0071] Generally, the smaller the average grain size of a metal solid, the smaller the strain of the metal solid as a whole becomes, and the larger the average grain size, the larger the strain of the metal solid as a whole becomes. However, the smaller the average grain size, the greater the deviation of the strain in the metal solid, which is prone to produce specific large deformation sites. On the contrary, the larger the average grain size, the smaller the deviation of the strain in the metal solid, which is not prone to produce specific large deformation sites.

[0072] Similarly, it is believed that for the metal substrate 11 with a small average grain size, when tensile stress is applied, the strain of the metal substrate 11 as a whole is small, but it is easy to produce a specific large deformation site. It is believed that the reason is that in the process of refining the grain size, there will be a site where the solute element is fixed to the movable dislocation, resulting in a small strain site and a large deformation site. And it is believed that in the site of the large deformation, the oxide superconducting layer 13 will crack, resulting in a reduction in superconducting properties. On the other hand, it is believed that for the metal substrate 11 with a large average grain size, when tensile stress is applied, the strain of the metal substrate 11 as a whole becomes larger, but it is not easy to produce a specific large deformation site. It is believed that therefore, the oxide superconducting layer 13 is not easy to crack, and the superconducting properties are ensured. Therefore, it is concluded that the larger the average grain size of the metal substrate 11, the greater the tensile resistance (the amount of strain allowed in LN2). Furthermore, according to the above-mentioned study, it is expected that even when the average grain size of the metal substrate 11 is larger than 16.20 μm (Example 15), the allowable strain amount in LN 2 will also increase.

[0073] In addition, in the process of forming the intermediate layer 12 or the oxide superconducting layer 13, high heat is applied to the metal substrate 11. This heat will induce the recrystallization of the metal contained in the metal substrate 11. Generally, if the rolled metal is recrystallized, the grain size will become smaller, so from the perspective of increasing the allowable strain in LN2, it is expected that no recrystallization will be performed. If recrystallization is almost completely performed, most of the grains present in the metal substrate 11 will have a small diameter, so the standard deviation of the grain size will become smaller. On the contrary, when recrystallization is almost not performed, grains with small diameters and grains with large diameters will be mixed in the metal substrate 11, so the standard deviation of the grain size will become larger. Therefore, the large standard deviation of the grain size of the metal substrate 11 means that the metal contained in the metal substrate 11 is almost not recrystallized. That is, in Comparative Examples 1 to 6, since the standard deviation of the grain size of the metal substrate 11 is small to a certain extent (less than 2.32μm), it is considered that recrystallization is almost completely performed and the average grain size becomes smaller. On the other hand, in Examples 1 to 18, since the standard deviation of the crystal grain size of the metal substrate 11 was large to a certain extent (2.32 μm or more), it is considered that recrystallization hardly proceeded and the average crystal grain size became large.

[0074] Based on the above, the present embodiment proposes a scheme of an oxide superconducting wire 10, which includes a strip-shaped metal substrate 11 made of a nickel alloy, an intermediate layer 12 stacked on the metal substrate 11, and an oxide superconducting layer 13 stacked on the intermediate layer 12, wherein the average grain size of the metal substrate 11 is greater than or equal to 3.08 μm and less than or equal to the thickness of the metal substrate. In addition, the upper limit of the average grain size of the metal substrate 11 is based on the average grain size of the metal substrate 11 not exceeding the thickness of the metal substrate 11.

[0075] This configuration makes it possible to realize an oxide superconducting wire having a high allowable strain amount in LN 2 , that is, an oxide superconducting wire whose superconducting characteristics are not easily degraded even when tensile stress is applied.

[0076] Furthermore, the standard deviation of the crystal grain size of the metal substrate 11 is in the range of 2.32 to 14.66 μm. With this configuration, it is possible to realize an oxide superconducting wire having a metal substrate 11 that is hardly recrystallized and has high tensile resistance.

[0077] In addition, the technical scope of the present invention is not limited to the above-described embodiments, and various modifications can be made within the scope not departing from the gist of the present invention.

[0078] For example, the oxide superconducting wire 10 may not include the protective layer 14 or the stabilizing layer 16 .

[0079] In addition, if Figure 3 As shown, a pancake-shaped multilayer winding coil (superconducting coil 100) can be formed by winding a tape-shaped oxide superconducting wire 10 multiple times in the thickness direction and stacking them.

[0080] For example, the superconducting coil 100 includes a laminated body and an impregnation resin layer, wherein the laminated body is formed by alternately laminating oxide superconducting wires 10 and metal tapes. The impregnation resin layer is impregnated into the laminated body and covers the outer surface of the laminated body. Examples of the resin constituting the impregnation resin layer include epoxy resin, phenolic resin, and the like.

[0081] The superconducting coil 100 can be manufactured, for example, by a method in which an oxide superconducting wire 10 coated with a resin (epoxy resin, etc.) is coiled together with a metal tape, and then the resin is cured by heating, etc. As a method for manufacturing the superconducting coil 100, a method in which an oxide superconducting wire 10 is coiled together with a metal tape, and then the resin is impregnated into the coil under reduced pressure, and then the resin is cured by heating, etc. may be adopted.

[0082] Such superconducting coil 100 can be used in superconducting magnets, superconducting motors, and the like.

[0083] In addition, you can Figures 4A to 4C As shown, superconductors 101, 102, and 103 are formed by assembling a plurality of tape-shaped oxide superconducting wires 10. A current of tens to hundreds of amperes can flow through one oxide superconducting wire 10, but a larger current can flow through a plurality of oxide superconducting wires 10 bundled together to form superconductors 101, 102, and 103. Furthermore, superconductors 101, 102, and 103 can be easily wound.

[0084] As an example of superconductors, there are: Figure 4A As shown, a spiral superconductor 101 is formed by spirally winding N strip-shaped oxide superconducting wires 10 - 1 to 10 - n around a core C, and further providing a cladding layer J on the outer periphery thereof.

[0085] As another example of superconductors, there are: Figure 4B As shown, a stacked superconductor 102 is obtained by stacking a plurality of oxide superconducting wires 10 and covering the outer periphery of the stacked body with a stabilizing material S.

[0086] As another example of superconductors, we can cite: Figure 4C As shown, a ROEBEL type superconductor 103 is formed by patterning and twisting a plurality of oxide superconducting wires 10 bundled at a bundle portion B so as to form a meandering shape.

[0087] In addition, the components in the above-described embodiment can be appropriately replaced with known components within the scope not departing from the gist of the present invention, and the above-described embodiment and modified examples can be appropriately combined.

[0088] Description of Reference Numerals

[0089] 10: oxide superconducting wire; 11: metal substrate; 12: intermediate layer; 13: oxide superconducting layer; 100: superconducting coil; 101, 102, 103: superconductors.

Claims

1. An oxide superconducting wire comprising: A metal substrate in the form of a strip made of a nickel alloy; an intermediate layer laminated on the metal substrate; and an oxide superconducting layer stacked on the intermediate layer, The average grain size of the metal substrate is greater than or equal to 3.08 μm and less than or equal to the thickness of the metal substrate.

2. The oxide superconducting wire according to claim 1, wherein The standard deviation of the grain size of the metal substrate is in the range of 2.32 to 14.66 μm.

3. The oxide superconducting wire according to claim 1 or 2, wherein: The average grain size is an average value of grain sizes in a cross section along the length direction and the thickness direction of the metal substrate.

4. The oxide superconducting wire according to any one of claims 1 to 3, wherein The average crystallite size is an average value of crystallite sizes measured by a reflection electron backscatter diffraction method. 5 . A superconducting coil formed by winding the oxide superconducting wire according to claim 1 . 6 . A superconductor obtained by assembling a plurality of the oxide superconducting wires according to claim 1 .

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