Superconducting wire

Abstract

A superconducting wire material (100) includes a base material (10), an intermediate layer (20), a superconducting layer (30), and a plurality of first precipitates (40) and / or a plurality of second precipitates (42). The base material (10) includes a first main surface (10a). The intermediate layer (20) includes a second main surface (20a) and a third main surface (20b) that is a surface opposite the second main surface (20a); and the second main surface (20a) is disposed on the base material (10) so as to face the first main surface (10a). The superconducting layer (30) is disposed on the third main surface (20b). The constituent material of the superconducting layer (30) is REBa2Cu3Ox (where RE is a rare earth element). The plurality of first precipitates (40) and the plurality of second precipitates (42) are dispersed in the superconducting layer (30). The constituent material of each of the plurality of first precipitates (40) and the constituent material of each of the plurality of second precipitates (42) are non-superconductors. In a cross-sectional view orthogonal to the third main surface (20b), an aspect ratio of each of the plurality of first precipitates (40) is greater than 1.

Description

[Technical Field]

[0001] The present disclosure relates to a superconducting wire. This application claims priority to Japanese Patent Application No. 2022-198562, filed December 13, 2022. The entire contents of this Japanese patent application are incorporated herein by reference. [Background technology]

[0002] For example, International Publication No. 2017 / 217487 (Patent Document 1) describes a superconducting wire. The superconducting wire described in Patent Document 1 includes a substrate, an intermediate layer, a superconducting layer, and a plurality of artificial pin rods.

[0003] The substrate has a first main surface. The intermediate layer has a second main surface and a third main surface opposite the second main surface. The intermediate layer is disposed on the substrate such that the second main surface faces the first main surface. The superconducting layer is disposed on the third main surface. A plurality of artificial pin rods are dispersed in the superconducting layer.

[0004] The superconducting layer is made of REBa2Cu3O x (RE is a rare earth element). The constituent material of each of the plurality of artificial pin rods is RE2O3 or BaMO3 (M is a tetravalent metal element). The c-axis direction of the superconducting layer is along the normal direction of the third principal surface. The longitudinal direction of the artificial pin rod is along the c-axis direction of the superconducting layer. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2017 / 217487 Summary of the Invention

[0006] The superconducting wire of the present disclosure comprises a substrate, an intermediate layer, a superconducting layer, and at least one of a plurality of first precipitates and a plurality of second precipitates. The substrate has a first main surface. The intermediate layer has a second main surface and a third main surface opposite the second main surface, and is disposed on the substrate so that the second main surface faces the first main surface. The superconducting layer is disposed on the third main surface. The constituent material of the superconducting layer is REBa2Cu3O x (RE is a rare earth element). The plurality of first precipitates and the plurality of second precipitates are dispersed in the superconducting layer. The constituent material of each of the plurality of first precipitates and the constituent material of each of the plurality of second precipitates is a non-superconductor. In a cross-sectional view perpendicular to the third main surface, the aspect ratio of each of the plurality of first precipitates is greater than 1. In the cross-sectional view, the longitudinal direction of each of the plurality of first precipitates forms an angle of 20° or less with respect to the third main surface. In the cross-sectional view, the plurality of second precipitates are arranged in rows to form a group. In the cross-sectional view, the arrangement direction of the plurality of second precipitates forming a group forms an angle of 20° or less with respect to the third main surface. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a cross-sectional view of a superconducting wire 100 . [Figure 2A] FIG. 2A is an enlarged view of a portion of FIG. [Figure 2B] FIG. 2B is a partially enlarged view of the vicinity of the end of the precipitate 40 in the longitudinal direction. [Figure 3A] FIG. 3A is a first enlarged cross-sectional view of superconducting wire 100 according to Modification 1. FIG. [Figure 3B] FIG. 3B is a second enlarged cross-sectional view of superconducting wire 100 according to Modification 1. As shown in FIG. [Figure 4] FIG. 4 is an enlarged cross-sectional view of superconducting wire 100 according to Modification 2. As shown in FIG. [Figure 5] FIG. 5 is an enlarged cross-sectional view of superconducting wire 100 according to Modification 3. As shown in FIG. [Figure 6] FIG. 6 is an enlarged cross-sectional view of superconducting wire 100 according to the fourth modification. [Figure 7]FIG. 7 is an enlarged cross-sectional view of superconducting wire 100 according to Modification 5. As shown in FIG. [Figure 8] FIG. 8 is a diagram showing the manufacturing process of superconducting wire 100. [Figure 9] FIG. 9 is a cross-sectional view illustrating the preparation step S1. [Figure 10] FIG. 10 is a cross-sectional view illustrating the intermediate layer forming step S2. [Figure 11] FIG. 11 is a cross-sectional view illustrating the superconducting layer forming step S3. DETAILED DESCRIPTION OF THE INVENTION

[0008] [Problem to be solved by this disclosure] The superconducting wire described in Patent Document 1 has room for improvement in low-temperature magnetic field characteristics. The present disclosure has been made in consideration of the problems of the conventional technology as described above. More specifically, the present disclosure provides a superconducting wire that can improve low-temperature magnetic field characteristics. [Effects of this disclosure] The superconducting wire of the present disclosure can improve low-temperature magnetic field characteristics.

[0009] [Description of the embodiments of the present disclosure] First, embodiments of the present disclosure will be listed and described.

[0010] (1) A superconducting wire according to an embodiment includes a substrate, an intermediate layer, a superconducting layer, and at least one of a plurality of first precipitates and a plurality of second precipitates. The substrate has a first main surface. The intermediate layer has a second main surface and a third main surface opposite the second main surface, and is disposed on the substrate so that the second main surface faces the first main surface. The superconducting layer is disposed on the third main surface. The constituent material of the superconducting layer is REBa2Cu3O x(RE is a rare earth element). The plurality of first precipitates and the plurality of second precipitates are dispersed in the superconducting layer. The constituent material of each of the plurality of first precipitates and the constituent material of each of the plurality of second precipitates is a non-superconductor. In a cross-sectional view perpendicular to the third main surface, the aspect ratio of each of the plurality of first precipitates is greater than 1. In the cross-sectional view, the longitudinal direction of each of the plurality of first precipitates forms an angle of 20° or less with respect to the third main surface. In the cross-sectional view, the plurality of second precipitates are arranged in rows to form a group. In the cross-sectional view, the arrangement direction of the plurality of second precipitates forming a group forms an angle of 20° or less with respect to the third main surface.

[0011] The superconducting wire of (1) above can improve low-temperature magnetic field characteristics. (2) In the superconducting wire of (1) above, the constituent material of each of the plurality of first precipitates may be a metal oxide.

[0012] (3) In the superconducting wire of (1) or (2), the constituent material of each of the plurality of first precipitates may be RE2O3 or BaMO3 (M is a tetravalent metal element).

[0013] (4) In the superconducting wire according to any one of (1) to (3) above, the average aspect ratio of the plurality of first precipitates may be 2 or more.

[0014] (5) In the superconducting wire of (1) to (4), third precipitates may be further dispersed in the superconducting layer. The constituent material of the third precipitates may be a non-superconductor. In a cross-sectional view, the third precipitates may be granular.

[0015] The superconducting wire of (5) above can further improve the low-temperature magnetic field characteristics. (6) In the superconducting wire of (1) to (5) above, when viewed in cross section, the maximum distance between two adjacent first precipitates in a direction parallel to the third main surface may be 1500 nm or less.

[0016] The superconducting wire of (6) above can further improve the low-temperature magnetic field characteristics. (7) In the superconducting wire of (1) to (6) above, when viewed in cross section, the maximum value of the spacing between two adjacent first precipitates in a direction perpendicular to the third main surface may be 500 nm or less.

[0017] The superconducting wire of (7) above can further improve the low-temperature magnetic field characteristics. (8) In the superconducting wire according to any one of (1) to (7) above, the minimum and maximum widths of each of the plurality of first precipitates in the longitudinal direction may be 10 nm or more and 2000 nm or less, respectively, in a cross-sectional view.

[0018] The superconducting wire of (8) above can further improve the low-temperature magnetic field characteristics. (9) In the superconducting wire according to any one of (1) to (8) above, the maximum width of each of the plurality of first precipitates in a direction perpendicular to the longitudinal direction may be 200 nm or less in a cross-sectional view.

[0019] The superconducting wire of (9) above can further improve the low-temperature magnetic field characteristics. (10) In the superconducting wire according to any one of (1) to (9), in a cross-sectional view, at least one of the plurality of first precipitates may have a first protrusion protruding in a direction perpendicular to the longitudinal direction between both ends thereof in the longitudinal direction. In a cross-sectional view, the group may have a second protrusion protruding in a direction perpendicular to the arrangement direction between both ends thereof in the arrangement direction.

[0020] The superconducting wire of (10) above can further improve the low-temperature magnetic field characteristics. (11) In the superconducting wire of (1) to (10) above, each of the plurality of first precipitates may have a tip portion at the end in the longitudinal direction, the width of which in a direction perpendicular to the longitudinal direction decreases as it approaches the end.

[0021] The superconducting wire of (11) above can further improve the low-temperature magnetic field characteristics. [Details of the embodiments of the present disclosure] Next, details of an embodiment of the present disclosure will be described with reference to the drawings. In the following drawings, the same or corresponding parts are designated by the same reference numerals, and redundant description will not be repeated. A superconducting wire according to the embodiment is referred to as a superconducting wire 100.

[0022] <Configuration of Superconducting Wire 100> The configuration of superconducting wire 100 will be described below.

[0023] Fig. 1 is a cross-sectional view of a superconducting wire 100. Fig. 2A is an enlarged view of a portion of Fig. 1. As shown in Figs. 1 and 2A, the superconducting wire 100 has a substrate 10, an intermediate layer 20, a superconducting layer 30, and a plurality of precipitates 40.

[0024] The substrate 10 has a main surface 10a and a main surface 10b. The main surface 10a and the main surface 10b are end surfaces in the thickness direction of the substrate 10. The main surface 10b is the surface opposite to the main surface 10a.

[0025] The substrate 10 is a clad material having, for example, a stainless steel tape member, a copper (Cu) layer disposed on the tape member, and a nickel (Ni) layer disposed on the copper layer. In the copper layer, copper crystal grains are crystalline oriented. Therefore, the nickel layer is also crystalline oriented along the crystalline orientation of the copper layer. The nickel layer forms the main surface 10a. The substrate 10 may be Hastelloy (registered trademark). The substrate 10 may also be a tape member made of a biaxially oriented metal material or a tape member made of a non-oriented metal material.

[0026] The intermediate layer 20 has a principal surface 20a and a principal surface 20b. The principal surface 20a and the principal surface 20b are end surfaces in the thickness direction of the intermediate layer 20. The principal surface 20b is the surface opposite to the principal surface 20a. The intermediate layer 20 is disposed on the principal surface 10a so that the principal surface 20a faces the principal surface 10a.

[0027] The intermediate layer 20 has, for example, an yttrium oxide (Y2O3) layer, an yttria-stabilized zirconium oxide (YSZ) layer, and a cerium oxide (CeO2) layer. The yttrium oxide layer is disposed on the main surface 10a. The yttria-stabilized zirconium oxide layer is disposed on the yttrium oxide layer. The cerium oxide layer is disposed on the yttria-stabilized zirconium oxide layer. Note that the intermediate layer 20 does not necessarily have to have at least one of the yttria-stabilized zirconium oxide layer and the cerium oxide layer. As described above, since the nickel layer of the substrate 10 is crystalline oriented, each layer of the intermediate layer 20 has a crystalline orientation that follows the crystalline orientation of the nickel layer of the substrate 10. When the substrate 10 is Hastelloy, the intermediate layer 20 has, for example, an aluminum oxide (Al2O3) layer, an yttrium oxide layer, and a magnesium oxide layer. (MgO) In this case, the intermediate layer 20 does not necessarily have to include the cerium oxide layer.

[0028] The superconducting layer 30 is disposed on the intermediate layer 20 (on the main surface 20b). The constituent material of the superconducting layer 30 is a superconductor. More specifically, the constituent material of the superconducting layer 30 is REBa2Cu3O x (RE is a rare earth element). Examples of rare earth elements include gadolinium (Gd), yttrium (Y), eurobium (Eu), holmium (Ho), ytterbium (Yb), samarium (Sm), dysprosium (Dy), and neodymium (Nd). Rare earth elements are not limited to these. As described above, intermediate layer 20 is crystalline oriented, and therefore superconducting layer 30 has a crystalline orientation along the crystalline orientation of intermediate layer 20. More specifically, superconducting layer 30 has a crystalline orientation such that the c-axis direction of superconducting layer 30 is aligned with the normal direction of main surface 20b.

[0029] Although not shown, the superconducting wire 100 may further include a protective layer and a stabilizing layer. The protective layer is made of, for example, silver or a silver alloy, and the stabilizing layer is made of, for example, copper or a copper alloy. The protective layer is disposed on the superconducting layer 30, and the stabilizing layer is disposed on the protective layer.

[0030] A plurality of precipitates 40 are dispersed in the superconducting layer 30. The constituent material of the precipitates 40 is a non-superconductor. The constituent material of the precipitates 40 is, for example, a metal oxide. The constituent material of the precipitates 40 is, for example, RE2O3. The rare earth element contained in the constituent material of the precipitates 40 is, for example, the same as the rare earth element contained in the constituent material of the superconducting layer 30. The constituent material of the precipitates 40 may be BaMO3 (M is a tetravalent metal element). The tetravalent metal element is, for example, hafnium (Hf), zirconium (Zr), tin (Sn), titanium (Ti), etc.

[0031] In a cross-sectional view, the width of the precipitate 40 in the longitudinal direction is defined as width W1. A cross-sectional view refers to the case where the superconducting layer 30 is observed in any cross section perpendicular to the main surface 20b. The longitudinal direction of the precipitate 40 is the direction in which the width of the precipitate 40 is greatest. In a cross-sectional view, the width of the precipitate 40 in a direction perpendicular to the longitudinal direction is defined as width W2. Width W1 is larger than width W2.

[0032] In a cross-sectional view, the aspect ratio of the precipitate 40 is the value obtained by dividing the width W1 by the width W2. In a cross-sectional view, the aspect ratio of the precipitate 40 is greater than 1. Furthermore, the three-dimensional shape of the precipitate 40 may be rod-like, plate-like, or disk-like. In a cross-sectional view, the average value of the aspect ratios of the precipitates 40 for a plurality of precipitates 40 may be 2 or more, or 5 or more. In a cross-sectional view, the average value of the aspect ratios of the precipitates 40 for a plurality of precipitates 40 is calculated by the following method.

[0033] First, a transmission electron microscope (TEM) is used to obtain a TEM image of the superconducting layer 30 in any cross section of the superconducting layer 30 perpendicular to the main surface 20b. The TEM image is obtained at a magnification (first magnification) such that at least 50 precipitates 40 are present within the observation field. Second, the width W1 and width W2 of each of the plurality of precipitates 40 present within the observation field are measured, thereby calculating the aspect ratio of each of the plurality of precipitates 40 present within the observation field. When measuring the width W1 and width W2, the TEM image is magnified at a second magnification greater than the first magnification. Third, the sum of the aspect ratios of each of the plurality of precipitates 40 present within the observation field divided by the number of the plurality of precipitates 40 present within the observation field is considered to be the average aspect ratio of the precipitates 40 for the plurality of precipitates 40 in the superconducting layer 30. The first magnification and the second magnification are, for example, 50,000 times and 200,000 times, respectively.

[0034] The minimum value of width W1 is, for example, 10 nm or more, 20 nm or more, or 40 nm or more. The maximum value of width W1 is, for example, 2000 nm or less, 1800 nm or less, or 1500 nm or less. The minimum value of width W2 is, for example, 1 nm or more, 4 nm or more, or 10 nm or more. The maximum value of width W2 is, for example, 200 nm or less, 150 nm or less, or 80 nm or less. As shown in FIG. 2A , in a precipitate 40 having a tip 40c (tip 40d) where width W2 is reduced, width W2 at tip 40c (tip 40d) is very close to zero.

[0035] The minimum and maximum values ​​of width W1 and the minimum and maximum values ​​of width W2 are measured by the following method. First, a TEM image of the superconducting layer 30 is obtained in any cross section of the superconducting layer 30 perpendicular to the main surface 20b using a TEM. The TEM image is obtained at a magnification (first magnification) such that at least 50 precipitates 40 are present within the observation field. Second, the width W1 is measured for each of the multiple precipitates 40 present within the observation field. When measuring the width W1, the TEM image is magnified by a second magnification greater than the first magnification. Third, the largest value of the widths W1 measured in this manner is considered to be the maximum value of width W1, and the smallest value of the widths W1 measured in this manner is considered to be the minimum value of width W1. The first and second magnifications are, for example, 50,000 times and 200,000 times, respectively. The maximum and minimum values ​​of width W2 are calculated by a similar method.

[0036] In a cross-sectional view, a direction parallel to the main surface 20b is defined as a first direction DR1, and a direction perpendicular to the main surface 20b is defined as a second direction DR2. In a cross-sectional view, the plurality of precipitates 40 are arranged in a plurality of rows along the first direction DR1. The rows of the precipitates 40 are arranged along the first direction DR1 even if the direction in which the precipitates 40 are arranged is not parallel to the first direction DR1. The rows of the plurality of precipitates 40 are arranged at intervals in the second direction DR2.

[0037] The distance in the first direction DR1 between two adjacent precipitates 40 in the first direction DR1 is defined as a distance SP1. The distance in the second direction DR2 between two adjacent precipitates 40 in the second direction DR2 is defined as a distance SP2.

[0038] The maximum value of the spacing SP1 is, for example, 1500 nm or less, 1000 nm or less, or 500 nm or less. The minimum value of the spacing SP1 is, for example, 8 nm or more, 10 nm or more, or 15 nm or more. The maximum value of the spacing SP2 is, for example, 500 nm or less, 400 nm or less, or 300 nm or less. The minimum value of the spacing SP2 is, for example, 2 nm or more, 3 nm or more, or 15 nm or more.

[0039] The minimum and maximum values ​​of the spacing SP1 and the minimum and maximum values ​​of the spacing SP2 are calculated by the following method. First, a TEM is used to obtain a TEM image of the superconducting layer 30 in any cross section of the superconducting layer 30 perpendicular to the main surface 20b. The TEM image is obtained at a magnification (first magnification) such that at least 50 precipitates 40 are present within the observation field. Second, the spacing SP1 is measured for all of the multiple precipitates 40 present within the observation field. When measuring the spacing SP1, the TEM image is magnified by a second magnification greater than the first magnification. Third, the largest value of the spacing SP1 measured in this manner is considered to be the maximum value of the spacing SP1 in the superconducting layer 30, and the smallest value of the spacing SP1 measured in this manner is considered to be the minimum value of the spacing SP1. The first and second magnifications are, for example, 50,000 times and 200,000 times, respectively. The maximum and minimum values ​​of the spacing SP2 are also calculated by a similar method.

[0040] The angle between the longitudinal direction of the precipitate 40 and the main surface 20b in a cross-sectional view is defined as the inclination angle θ1. The longitudinal direction of the precipitate 40 in a cross-sectional view is regarded as the direction of a straight line L1 defined as follows. First, straight lines L2 and L3 are determined. The straight lines L2 and L3 are perpendicular to the main surface 20b and sandwich the precipitate 40. The tangent point between the straight line L2 and the precipitate 40 is defined as the tangent point P1. The tangent point between the straight line L3 and the precipitate 40 is defined as the tangent point P2. The straight line L1 passes through the tangent points P1 and P2. The width W1 corresponds to the length of the straight line L1. The inclination angle θ1 is 20° or less. The inclination angle θ1 may be 10° or less. The inclination angle θ1 is calculated by the following method.

[0041] First, a TEM image of the superconducting layer 30 is obtained at a cross section of any superconducting layer 30 perpendicular to the main surface 20b using a TEM. The TEM image is obtained at a magnification (first magnification) such that at least 50 precipitates 40 are present within the observation field. Second, the tilt angle θ1 is measured for each of the multiple precipitates 40 present within the observation field. When measuring the tilt angle θ1, the TEM image is magnified by a second magnification greater than the first magnification. As a result, if the tilt angle θ1 is 20° or less for all of the multiple precipitates 40 present within the observation field, the relationship "tilt angle θ1 is 20° or less" is satisfied. The first and second magnifications are, for example, 50,000x and 200,000x, respectively.

[0042] In a cross-sectional view, both ends of the precipitate 40 in the longitudinal direction are referred to as end 40a and end 40b, respectively, and the end of the precipitate 40 in the longitudinal direction on the end 40a side and the end of the precipitate 40 in the longitudinal direction on the end 40b side are referred to as tip portion 40c and tip portion 40d, respectively. The width W2 of tip portion 40c in a direction perpendicular to the longitudinal direction of the precipitate 40 preferably decreases toward end 40a, and the width of tip portion 40d in the direction perpendicular to the longitudinal direction of the precipitate 40 preferably decreases toward end 40b.

[0043] In a cross-sectional view, the precipitate 40 may have a protrusion 40e between the end 40a and the end 40b. In a cross-sectional view, the protrusion 40e protrudes in a direction perpendicular to the longitudinal direction of the precipitate 40.

[0044] FIG. 2B is a partially enlarged view of the vicinity of an end portion of the precipitate 40 in the longitudinal direction. As shown in FIG. 2B, precipitates 41 may be further dispersed in the superconducting layer 30. In a cross-sectional view, the precipitate 41 is granular. The shape of the precipitate 41 in a cross-sectional view is, for example, a circle, an ellipse, a rectangle with rounded corners (square, rectangular), or a shape distorted (sheared) in a specific direction. The precipitates 41 are, for example, lined up along the longitudinal direction of the precipitate 40 near the end portion of the precipitate 40 in the longitudinal direction or in parallel with the precipitate 40. The constituent material of the precipitate 41 is a non-superconductor (e.g., a metal oxide such as RE2O3 or BaMO3). The minimum dimension of the precipitate 41 is, for example, 2 nm, and the maximum dimension of the precipitate 41 is approximately 16 nm.

[0045] <Variation 1> FIG. 3A is a first enlarged cross-sectional view of superconducting wire 100 according to Variation 1. FIG. 3B is a second enlarged cross-sectional view of superconducting wire 100 according to Variation 1. As shown in FIG. 3A, precipitates 42 may be dispersed in superconducting layer 30 instead of precipitates 40. As shown in FIG. 3B, precipitates 42 may be dispersed in superconducting layer 30 together with precipitates 40. The constituent material of precipitates 42 is a non-superconductor (e.g., a metal oxide such as RE2O3 or BaMO3). The plurality of precipitates 42 are arranged in a row to form group 43 in a cross-sectional view. There may be a plurality of groups 43 in superconducting layer 30. Note that group 43 may include precipitates 42 that are in contact with each other. From another perspective, group 43 may include two precipitates 42 whose spacing SP3, described below, is 0.

[0046] In a cross-sectional view, the direction in which the multiple precipitates 42 forming the group 43 are lined up is defined as the arrangement direction. The distance in the arrangement direction between two adjacent ones of the multiple precipitates 42 forming the group 43 is defined as the spacing SP3. The maximum value of the spacing SP3 is, for example, 50 nm or less, 30 nm or less, 20 nm or less, 10 nm or less, or 5 nm or less. The spacing SP3 may be substantially 0. That is, two adjacent precipitates 42 may be lined up in substantial contact with each other. The maximum value of the spacing SP3 is, for example, 1 / 50 or less of the spacing SP4 described below. The maximum value of the spacing SP3 is measured in the same manner as the maximum value of the spacing SP1 and the maximum value of the spacing SP2.

[0047] In a cross-sectional view, the aspect ratio of the group 43 is the value obtained by dividing the width of the group 43 in the arrangement direction by the width of the group 43 in a direction perpendicular to the arrangement direction. The aspect ratio of the group 43 is 1 or greater. The aspect ratio of the group 43 may be greater than 1. The aspect ratio of the group 43 is, for example, 3 or greater, or 5 or greater. The aspect ratio of the precipitate 42 is the value obtained by dividing the width of the precipitate 42 in the longitudinal direction by the width of the precipitate 42 in a direction perpendicular to the longitudinal direction. The aspect ratio of the precipitate 42 may be, for example, 3 or less, less than 2, or 1.5 or less. Note that a precipitate 42 having an aspect ratio greater than 1 also corresponds to the precipitate 40. The aspect ratio of the precipitate 42 may be 0.3 or greater and 1 or less. A precipitate 42 having an aspect ratio less than 1 can form a protrusion 43a, which will be described later. The aspect ratios of the plurality of precipitates 42 belonging to the group 43 may differ from one another. The aspect ratios of the group 43 and the precipitates 42 are measured in the same manner as the aspect ratio of the precipitate 40.

[0048] In a cross-sectional view, the width in the arrangement direction of the groups 43 is defined as width W3, the width in the direction perpendicular to the arrangement direction of the groups 43 is defined as width W4, and width W5 is defined as the width in the arrangement direction of the precipitates 42 belonging to the groups 43. The minimum value of width W3 is, for example, 10 nm or more, 20 nm or more, or 30 nm or more. The maximum value of width W3 is, for example, 10,000 nm or less, 1,700 nm or less, or 900 nm or less. The minimum value of width W4 is, for example, 1 nm or more, 2 nm or more, or 3 nm or more. The maximum value of width W4 is, for example, 200 nm or less, 150 nm or less, 100 nm or less, or 80 nm or less. The minimum value of width W5 is, for example, 1 nm or more. The maximum value of width W5 is, for example, 100 nm or less, 60 nm or less, or 40 nm or less.

[0049] The angle between the arrangement direction and the main surface 20b in a cross-sectional view is defined as the inclination angle θ2. The arrangement direction is considered to be the direction of the line L4, which is defined as follows. First, lines L5 and L6 are determined. The lines L5 and L6 are perpendicular to the main surface 20b and sandwich the group 43. The point of contact between the line L5 and the precipitate 42 at the first end of the group 43 is defined as the tangent point P3. The point of contact between the line L6 and the precipitate 42 at the second end of the group 43 (the end opposite the first end) is defined as the tangent point P4. The line L4 passes through the tangent points P3 and P4. The inclination angle θ2 is 20° or less. The inclination angle θ2 is measured using the same method as the inclination angle θ1.

[0050] In a cross-sectional view, the distance between two adjacent groups 43 in the first direction DR1 is defined as distance SP4, and the distance between two adjacent groups 43 in the second direction DR2 is defined as distance SP5. The maximum value of distance SP4 is, for example, 2500 nm or less. The minimum value of distance SP4 is, for example, 2 nm or more. The maximum value of distance SP5 is, for example, 2000 nm or less. The minimum value of distance SP5 is, for example, 1 nm or more. The maximum and minimum values ​​of distance SP4 are measured in the same manner as the maximum and minimum values ​​of distance SP1, and the maximum and minimum values ​​of distance SP5 are measured in the same manner as the maximum and minimum values ​​of distance SP2.

[0051] <Variation 2> Fig. 4 is an enlarged cross-sectional view of superconducting wire 100 according to Variation 2. As shown in Fig. 4, in the cross-sectional view, the longitudinal direction of precipitates 42 may be a direction intersecting the arrangement direction. Group 43 may have, between both ends in the arrangement direction, a protruding portion 43a that protrudes in a direction perpendicular to the arrangement direction. Protruding portion 43a is formed by a portion of precipitates 42 that form group 43, and the aspect ratio of precipitates 42 included in that portion is smaller than the aspect ratios of the other precipitates 42 that form the group.

[0052] <Variation 3> Fig. 5 is an enlarged cross-sectional view of superconducting wire 100 according to Modification 3. As shown in Fig. 5, precipitates 41 may be dispersed evenly throughout superconducting layer 30 without being aligned along the longitudinal direction of precipitates 40.

[0053] <Modifications 4 and 5> FIG. 6 is an enlarged cross-sectional view of a superconducting wire 100 according to Modification 4. As shown in FIG. 6, precipitates 44 may be further dispersed in the superconducting layer 30. The constituent material of the precipitates 44 is a non-superconductor (e.g., a metal oxide such as RE2O3 or BaMO3). The aspect ratio of the precipitates 44 is the value obtained by dividing the width of the precipitates 44 in the longitudinal direction in a cross-sectional view by the width of the precipitates 44 in a direction perpendicular to the longitudinal direction. The aspect ratio of the precipitates 44 is greater than 1. The angle formed between the longitudinal direction of the precipitates 44 and the main surface 20b is, for example, 60° or greater.

[0054] FIG. 7 is an enlarged cross-sectional view of a superconducting wire 100 according to Modification 5. As shown in FIG. 7, precipitates 45 may be further dispersed in the superconducting layer 30. The constituent material of the precipitates 45 is a non-superconductor (e.g., a metal oxide such as RE2O3 or BaMO3). The plurality of precipitates 45 are arranged in rows to form groups 46 in a cross-sectional view. The angle between the direction in which the precipitates 45 forming the groups 46 are arranged and the main surface 20b is 60° or greater.

[0055] <Method for manufacturing superconducting wire 100> A method for manufacturing the superconducting wire 100 will be described below.

[0056] Fig. 8 is a manufacturing process diagram of superconducting wire 100. As shown in Fig. 8, the manufacturing method of superconducting wire 100 includes a preparation step S1, an intermediate layer forming step S2, and a superconducting layer forming step S3. The intermediate layer forming step S2 is performed after the preparation step S1. The superconducting layer forming step S3 is performed after the intermediate layer forming step S2.

[0057] FIG. 9 is a cross-sectional view illustrating the preparation step S1. As shown in FIG. 9, in the preparation step S1, a substrate 10 is prepared. The substrate 10 prepared in the preparation step S1 does not have an intermediate layer 20 disposed on the main surface 10a. FIG. 10 is a cross-sectional view illustrating the intermediate layer formation step S2. As shown in FIG. 10, in the intermediate layer formation step S2, an intermediate layer 20 with oriented crystals is formed on the main surface 10a. The intermediate layer 20 is formed by sequentially depositing each layer that constitutes the intermediate layer 20 using, for example, magnetron sputtering, ion beam sputtering, or PLD (Pulsed Laser Deposition).

[0058] FIG. 11 is a cross-sectional view illustrating the superconducting layer forming step S3. As shown in FIG. 11, in the superconducting layer forming step S3, first, a superconducting layer 31 is formed on the intermediate layer 20. The superconducting layer 31 is thinner than the superconducting layer 30. The superconducting layer 31 is formed by, for example, a metal organic decomposition (MOD) method, a metal organic chemical vapor deposition (MOCVD) method, or a PLD method. During this process, the rare earth elements deviate from the stoichiometric composition, causing precipitates 40 to precipitate on the surface or inside of the superconducting layer 31. Second, another superconducting layer 31 is formed by a similar method on the already formed superconducting layer 31. By repeating this process, a plurality of superconducting layers 31 become the superconducting layer 30, and the superconducting wire 100 having the structure shown in FIGS. 1 and 2A is manufactured.

[0059] The precipitates 40, 41, and 42 are deposited on the surface or inside of the superconducting layer 31 by repeatedly laminating layers in the superconducting layer forming step S3.

[0060] <Effects of Superconducting Wire 100> The effects of superconducting wire 100 will be described below in comparison with comparative examples. Superconducting wire according to comparative example 1 and superconducting wire according to comparative example 2 are designated as superconducting wire 100A and superconducting wire 100B, respectively.

[0061] The structure of superconducting wire 100A differs from that of superconducting wire 100 in that precipitates 40 are not dispersed in superconducting layer 30. In superconducting wire 100B, granular precipitates are dispersed in superconducting layer 30. These precipitates are BaZr2O3 and function as magnetic flux pins. In this respect, the structure of superconducting wire 100B differs from that of superconducting wire 100.

[0062] Samples 1 to 6 were prepared as superconducting wire samples. Samples 1 and 2 correspond to superconducting wire 100A and superconducting wire 100B, respectively. Samples 3 to 6 correspond to superconducting wire 100. As shown in Table 1, the type of precipitate (precipitate 40, which is the first precipitate, and precipitate 42, which is the second precipitate), the aspect ratio of precipitate 40, the average aspect ratio of precipitate 40, the inclination angle θ1 or θ2, the widths W1 to W5, and the spacings SP1 to SP5 were changed in Samples 1 to 6. The numerical ranges shown in Table 1 represent the results of measuring the widths and angles of 10 or more precipitates from the observation field set as described above. For example, the width W1 of Sample 4 was within the range of 10 nm to 350 nm. The average values ​​of the tilt angle θ1, the tilt angle θ2, and the aspect ratio of the precipitate 40 are average values ​​for 10 or more precipitates. In Sample 1 and Sample 2, no precipitates were present. In Sample 3, the precipitate 42 was present, and in Sample 4, the precipitate 40 and the precipitate 42 were present. In Sample 5, the precipitate 40 was present. In Sample 6, the precipitate 42 was present.

[0063] Although not shown in Table 1, in Sample 4, the group 43 of precipitates 42 had a protrusion 43a, and the precipitate 40 had a tip 40c (tip 40d) whose width W2 became smaller as it approached the end 40a (end 40b), and precipitates 41 were deposited. In Sample 5, the precipitate 40 had a protrusion 40e, and the precipitate 40 had a tip 40c (tip 40d) whose width W2 became smaller as it approached the end 40a (end 40b), and precipitates 41 were deposited. In Sample 6, the group 43 of precipitates 42 had a protrusion 43a.

[0064] [Table 1]

[0065] The superconducting properties of each sample were measured. The Jc values ​​of each superconducting wire under a self-magnetic field at 77 K and under a 3 T magnetic field at 30 K were measured. The 3 T magnetic field was applied in a direction perpendicular to the main surface 20 b. Jc is the critical current density. The measurement results are shown in Table 2. The α value was calculated for each superconducting wire by dividing the Jc under a 3 T magnetic field at 30 K by the Jc under a self-magnetic field at 77 K, and serves as an index of low-temperature magnetic field properties. The larger the α value, the better the low-temperature magnetic field properties. The Jc was calculated from the critical current value (Ic) measured for each sample with the superconducting layer 30 having a thickness of 3±0.5 μm and a width of 4 mm.

[0066] [Table 2]

[0067] As shown in Table 2, the values ​​of α in Samples 3 to 6 were larger than the values ​​of α in Samples 1 and 2. Furthermore, Samples 3 to 6 satisfied at least one of the following conditions: (a) the aspect ratio of the precipitates 40 is larger than 1 and the inclination angle θ1 is 20° or less; and (b) the precipitates 42 are arranged in rows to form groups 43 and the inclination angle θ2 is 20° or less. From this comparison, it can be seen that the conditions (a) and (b) At least one of It was experimentally revealed that the low-temperature magnetic field characteristics of the superconducting wire 100 are improved by satisfying the above condition. Furthermore, the value of α was highest in Sample 4, in which both the precipitates 40 and the group 43 of the precipitates 42 were present in the superconducting layer 30. Therefore, it was experimentally revealed that the low-temperature magnetic field characteristics are further improved by the presence of both the precipitates 40 and the group 43 of the precipitates 42 in the superconducting layer 30.

[0068] It is believed that both longitudinal ends of precipitates 40 function as magnetic flux pins that improve low-temperature magnetic field characteristics. Therefore, when the aspect ratio of precipitates 40 is greater than 1, the portions that function as magnetic flux pins can be regarded as being dispersed at intervals in superconducting layer 30, and therefore superconducting wire 100 is believed to have improved low-temperature magnetic field characteristics compared to superconducting wire 100A and superconducting wire 100B.

[0069] It is believed that the smaller the spacing SP1, the more easily precipitates 40 function as magnetic flux pins, and therefore, by setting the maximum value of spacing SP1 to 1500 nm or less, the low-temperature magnetic field characteristics of superconducting wire 100 are further improved. It is believed that the smaller the spacing SP2, the more easily precipitates 40 function as magnetic flux pins, and therefore, by setting the maximum value of spacing SP2 to 500 nm or less, the low-temperature magnetic field characteristics of superconducting wire 100 are further improved.

[0070] When the maximum and minimum values ​​of width W1 are 2000 nm or less and 10 nm or more, respectively, or when the maximum and minimum values ​​of width W2 are 200 nm or less and 1 nm or more, respectively, the portions of precipitates 40 that function as magnetic flux pins are appropriately dispersed, thereby further improving the low-temperature magnetic field characteristics of superconducting wire 100.

[0071] If the width of tip portion 40c (tip portion 40d) in a direction perpendicular to the longitudinal direction of precipitate 40 becomes smaller as it approaches end 40a (end 40b), it is believed that tip portion 40c (tip portion 40d) will be more likely to function as a magnetic flux pin, and therefore the low-temperature magnetic field characteristics of superconducting wire 100 will be further improved.

[0072] When the precipitate 40 has a protrusion 40e (the group 43 has a protrusion 43a), it is believed that the protrusion 40e (protrusion 43a) is more likely to function as a magnetic flux pin, thereby further improving the low-temperature magnetic field characteristics of the superconducting wire 100.

[0073] The embodiments disclosed herein are illustrative in all respects and should not be considered limiting. The scope of the present invention is defined by the claims, not by the above-described embodiments, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0074] 10 base material, 10a,10b main surface, 20 intermediate layer, 20a,20b main surface, 30,31 superconducting layer, 40 precipitate, 40a,40b edge, 40c,40d tip, 40e protrusion, 41,42 precipitate, 43 group, 43a protrusion, 44,45 precipitate, 46 Group, 100,100A,100B superconducting wire, DR1 first direction, DR2 second direction, S1 preparation process, S2 intermediate layer formation process, S3 superconducting layer formation process, SP1,SP2,SP3,SP4,SP5 spacing, W1,W2,W3,W4,W5 width, θ1 tilt angle, θ2 Tilt angle.

Claims

1. A substrate; The middle class and a superconducting layer; At least one of a plurality of first precipitates and a plurality of second precipitates, the substrate has a first major surface; the intermediate layer has a second main surface and a third main surface opposite to the second main surface, and is disposed on the base material such that the second main surface faces the first main surface; the superconducting layer is disposed on the third principal surface, The constituent material of the superconducting layer is REBa ２ Cu ３ O ｘ (RE is a rare earth element), the plurality of first precipitates and the plurality of second precipitates are dispersed in the superconducting layer, a constituent material of each of the plurality of first precipitates and a constituent material of each of the plurality of second precipitates is at least one of RE 2 O 3 and BaMO 3 (M is a tetravalent metal element); In a cross-sectional view perpendicular to the third main surface, an aspect ratio of each of the plurality of first precipitates is greater than 1; In the cross-sectional view, a longitudinal direction of each of the plurality of first precipitates forms an angle of 20° or less with respect to the third main surface, In the cross-sectional view, the second precipitates are arranged in a row to form a group, In the cross-sectional view, the direction in which the plurality of second precipitates forming the group are arranged forms an angle of 20° or less with respect to the third main surface.

2. The superconducting wire according to claim 1 , wherein the average aspect ratio of the plurality of first precipitates is 2 or more.

3. a third precipitate is further dispersed in the superconducting layer; the constituent material of the third precipitate is a non-superconductor; The superconducting wire according to claim 1 , wherein the third precipitates are granular in the cross-sectional view.

4. 2. The superconducting wire according to claim 1, wherein, in the cross-sectional view, the maximum value of the spacing in a direction parallel to the third main surface between two adjacent ones of the plurality of first precipitates in the direction parallel to the third main surface is 1500 nm or less.

5. 2. The superconducting wire according to claim 1, wherein, in the cross-sectional view, the maximum value of the spacing between two adjacent ones of the plurality of first precipitates in a direction perpendicular to the third main surface is 500 nm or less.

6. 2. The superconducting wire according to claim 1, wherein, in the cross-sectional view, the minimum and maximum widths of each of the plurality of first precipitates in the longitudinal direction are 10 nm or more and 2000 nm or less, respectively.

7. 2. The superconducting wire according to claim 1, wherein, in the cross-sectional view, each of the plurality of first precipitates has a maximum width of 200 nm or less in a direction perpendicular to the longitudinal direction.

8. In the cross-sectional view, at least one of the plurality of first precipitates has a first protrusion protruding along a direction perpendicular to the longitudinal direction between both ends in the longitudinal direction, 2 . The superconducting wire according to claim 1 , wherein, in the cross-sectional view, the group has a second protrusion protruding in a direction perpendicular to the arrangement direction between both ends in the arrangement direction.

9. 9. The superconducting wire according to claim 1, wherein each of the plurality of first precipitates has a tip portion at an end in the longitudinal direction, the tip portion having a width in a direction perpendicular to the longitudinal direction that decreases as the tip approaches the end.

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