JP2024043984A - Superconducting layer connection structure, superconducting wire, superconducting coil, superconducting equipment - Google Patents

Abstract

[Problem] To provide a connection structure of superconducting layers that can achieve low electrical resistance and high mechanical strength. [Solution] The connection structure of superconducting layers of an embodiment includes a first superconducting layer, a second superconducting layer, and a connection layer provided between the first and second superconducting layers and containing crystal particles containing a rare earth element (RE), barium (Ba), copper (Cu), and oxygen (O), the connection layer includes a first region, a second region, and a third region provided between the first and second regions, the first region and the second region contain crystal particles, the third region contains or does not contain crystal particles, the third region is exposed to a side surface of the connection layer, and in a cross section perpendicular to the interface between the first superconducting layer and the connection layer and including the first region, the second region, and the third region, a first occupancy ratio of the crystal particles in the first region and a second occupancy ratio of the crystal particles in the second region are greater than a third occupancy ratio of the crystal particles in the third region. [Selected figure] Figure 3

Description

Embodiments of the present invention relate to a connection structure of a superconducting layer, a superconducting wire, a superconducting coil, and a superconducting device.

For example, in nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI) devices, superconducting coils are used to generate strong magnetic fields. Superconducting coils are formed by winding superconducting wire around a reel.

In order to lengthen the superconducting wire, for example, a plurality of superconducting wires are connected. For example, the ends of two superconducting wires are connected using a connection structure. Connection structures that connect superconducting wires are required to have low electrical resistance and high mechanical strength.

JP 2019-075201 A JP2019-075227A

The problem to be solved by the present invention is to provide a superconducting layer connection structure that can achieve low electrical resistance and high mechanical strength.

The superconducting layer connection structure of the embodiment is provided between a first superconducting layer, a second superconducting layer, and the first superconducting layer and the second superconducting layer, and includes a rare earth element (RE), a connection layer containing crystal particles containing barium (Ba), copper (Cu), and oxygen (O), the connection layer comprising a first region, a second region, and the first region. a third region provided between the region and the second region, the first region and the second region contain the crystal grains, and the third region contains the crystal grains. The third region is exposed on a side surface of the connection layer, and is perpendicular to the interface between the first superconducting layer and the connection layer and is located between the first region and the second region. , and in the cross section including the third region, the first occupancy ratio of the crystal grains in the first region and the second occupancy ratio of the crystal grains in the second region are the same as those in the third region. is larger than the third occupation ratio of the crystal grains.

FIG. 2 is a schematic cross-sectional view of the connection structure of superconducting layers according to the first embodiment. FIG. 3 is a schematic plan view of a connection layer of the first embodiment. FIG. 2 is an enlarged schematic cross-sectional view of a part of the connection layer of the first embodiment. FIG. 4 is a diagram illustrating the definition of the major axis and minor axis of a crystal grain according to the first embodiment. FIG. 4 is a diagram showing the major axis distribution of crystal particles contained in the connection layer according to the first embodiment. FIG. 4 is an enlarged schematic cross-sectional view of a portion of a connection layer of a first modified example of the first embodiment. FIG. 13 is a schematic plan view of a connection layer of a second modified example of the first embodiment. FIG. 13 is a schematic plan view of a connection layer of a third modified example of the first embodiment. FIG. 13 is a schematic plan view of a connection layer of a fourth modified example of the first embodiment. FIG. 7 is a schematic plan view of a connection layer of a fifth modification of the first embodiment. FIG. 11 is an enlarged schematic cross-sectional view of a portion of a connection layer according to a second embodiment. FIG. 13 is an enlarged schematic cross-sectional view of a portion of a connection layer according to a third embodiment. FIG. 13 is a diagram showing the major axis distribution of crystal particles contained in the connection layer according to the third embodiment. FIG. 4 is a schematic cross-sectional view of a superconducting wire according to a fourth embodiment. FIG. 13 is a schematic plan view of a connection layer according to a fourth embodiment. FIG. 13 is a schematic cross-sectional view of a first modified example of the superconducting wire of the fourth embodiment. FIG. 7 is a schematic cross-sectional view of a second modification of the superconducting wire of the fourth embodiment. FIG. 13 is a schematic cross-sectional view of a third modified example of the superconducting wire of the fourth embodiment. FIG. 7 is a schematic cross-sectional view of a fourth modification of the superconducting wire according to the fourth embodiment. FIG. 13 is a schematic perspective view of a superconducting coil according to a fifth embodiment. FIG. 7 is a schematic cross-sectional view of a superconducting coil according to a fifth embodiment. FIG. 7 is a block diagram of a superconducting device according to a sixth embodiment.

Embodiments of the present invention will be described below with reference to the drawings. In the following description, the same or similar members will be denoted by the same reference numerals, and the description of the members that have already been explained may be omitted as appropriate.

In this specification, the long axis of a particle is the maximum length between any two points on the periphery of the particle. The short axis of a particle is the length of a line segment that passes through the midpoint of the line segment corresponding to the long axis, is perpendicular to the line segment, and has the periphery of the particle as both ends. The long axis and short axis of a particle can be determined, for example, by image analysis of a cross-sectional image taken with a scanning electron microscope (SEM). In this specification, the line segment corresponding to the long axis is referred to as the long axis. The line segment corresponding to the short axis is referred to as the short axis.

In addition, the particle occupancy rate can be determined, for example, by image analysis of cross-sectional images taken with a scanning electron microscope (SEM).

The detection of elements contained in particles and the measurement of the atomic concentration of elements can be performed, for example, using energy dispersive X-ray spectroscopy (EDX) or wavelength dispersive X-ray analysis (WDX). Furthermore, the identification of substances contained in particles can be performed, for example, using powder X-ray diffraction.

First Embodiment
The connection structure of the superconducting layer of the first embodiment includes a first superconducting layer, a second superconducting layer, and a connection layer provided between the first superconducting layer and the second superconducting layer and containing crystal particles including a rare earth element (RE), barium (Ba), copper (Cu), and oxygen (O), the connection layer including a first region, a second region, and a third region provided between the first region and the second region, the first region and the second region containing crystal particles, the third region containing or not containing crystal particles, the third region being exposed to a side surface of the connection layer, and in a cross section perpendicular to the interface between the first superconducting layer and the connection layer and including the first region, the second region, and the third region, a first occupancy ratio of the crystal particles in the first region and a second occupancy ratio of the crystal particles in the second region are greater than a third occupancy ratio of the crystal particles in the third region.

FIG. 1 is a schematic cross-sectional view of the superconducting layer connection structure of the first embodiment. The connection structure 100 of the first embodiment is a structure that physically and electrically connects two superconducting layers. The connection structure 100 is used, for example, to connect two superconducting wires and to lengthen the superconducting wires.

The connection structure 100 includes a first superconducting member 10, a second superconducting member 20, and a connection layer 30. The connection structure 100 is a structure in which the first superconducting member 10 and the second superconducting member 20 are connected by the connection layer 30. The connection layer 30 is provided between the first superconducting member 10 and the second superconducting member 20.

The first superconducting member 10 includes a first substrate 12, a first intermediate layer 14, and a first superconducting layer 16. The second superconducting member 20 includes a second substrate 22, a second intermediate layer 24, and a second superconducting layer 26.

The first substrate 12 is, for example, a metal. The first substrate 12 is, for example, a nickel alloy or a copper alloy. The first substrate 12 is, for example, a nickel-tungsten alloy.

The first superconducting layer 16 is, for example, an oxide superconducting layer. The first superconducting layer 16 contains, for example, a rare earth element (RE), barium (Ba), copper (Cu), and oxygen (O). The first superconducting layer 16 includes, for example, yttrium (Y), lanthanum (La), neodymium (Nd), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), Contains at least one rare earth element (RE) from the group consisting of holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu).

The first superconducting layer 16 has _a chemical composition expressed, for example, as (RE) _Ba2Cu3Oδ ( _RE is _a rare earth element, 6≦δ≦7). The first superconducting layer 16 has a chemical composition expressed, for example, as _GdBa2Cu3Oδ (6≦δ≦ ₇ ), _YBa2Cu3Oδ (6≦δ≦7 ₎ , or _EuBa2Cu3Oδ (6≦ _{δ ≦} 7 ₎ .

The first superconducting layer 16 includes, for example, a single crystal having a perovskite structure.

The first superconducting layer 16 is formed on the first intermediate layer 14 by, for example, a metal organic decomposition method (MOD method), a pulsed laser deposition method (PLD method), or It is formed using a metal organic chemical vapor deposition method (MOCVD method).

The first intermediate layer 14 is provided between the first substrate 12 and the first superconducting layer 16. The first intermediate layer 14 is in contact with the first superconducting layer 16, for example. The first intermediate layer 14 has the function of improving the crystal orientation of the first superconducting layer 16 formed on the first intermediate layer 14.

The first intermediate layer 14 includes, for example, a rare earth oxide. The first intermediate layer 14 has, for example, a stacked structure of a plurality of films. The first intermediate layer 14 has, for example, a structure in which yttrium oxide (Y ₂ O ₃ ), yttria-stabilized zirconia (YSZ), and cerium oxide (CeO ₂ ) are stacked from the first substrate 12 side.

The second substrate 22 is, for example, a metal. The second substrate 22 is, for example, a nickel alloy or a copper alloy. The second substrate 22 is, for example, a nickel-tungsten alloy.

The second superconducting layer 26 is, for example, an oxide superconducting layer. The second superconducting layer 26 contains, for example, rare earth elements (RE), barium (Ba), copper (Cu), and oxygen (O). The first superconducting layer 16 includes, for example, yttrium (Y), lanthanum (La), neodymium (Nd), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), Contains at least one rare earth element (RE) from the group consisting of holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu).

The second superconducting layer 26 has, for example, a chemical composition expressed as (RE)Ba ₂ Cu ₃ O _δ (RE is a rare earth element, 6≦δ≦7). The second superconducting layer 26 is made of, for example, GdBa ₂ Cu ₃ O _δ (6≦δ≦7), YBa ₂ Cu ₃ O _δ (6≦δ≦7), or EuBa ₂ Cu ₃ O _δ (6≦δ≦ It has a chemical composition expressed as 7).

The second superconducting layer 26 includes, for example, a single crystal having a perovskite structure.

The second superconducting layer 26 is formed on the second intermediate layer 24, for example, using the MOD method, the PLD method, or the MOCVD method.

The second intermediate layer 24 is provided between the second substrate 22 and the second superconducting layer 26. The second intermediate layer 24 is in contact with the second superconducting layer 26, for example. The second intermediate layer 24 has the function of improving the crystal orientation of the second superconducting layer 26 formed on the second intermediate layer 24.

The second intermediate layer 24 includes, for example, a rare earth oxide. The second intermediate layer 24 has, for example, a laminated structure of a plurality of films. The second intermediate layer 24 has, for example, a structure in which yttrium oxide (Y ₂ O ₃ ), yttria-stabilized zirconia (YSZ), and cerium oxide (CeO ₂ ) are laminated from the second substrate 22 side.

The connection layer 30 is provided between the first superconducting layer 16 and the second superconducting layer 26. The connection layer 30 contacts the first superconducting layer 16. The connection layer 30 contacts the second superconducting layer 26.

Connection layer 30 is an oxide superconducting layer. The connection layer 30 contains rare earth elements (RE), barium (Ba), copper (Cu), and oxygen (O). The connection layer 30 is made of, for example, yttrium (Y), lanthanum (La), neodymium (Nd), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), or holmium (Ho). ), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu).

The connection layer 30 includes a plurality of high density regions 30a and at least one low density region 30b.

The plurality of high-density regions 30a include a first high-density region 30a1, a second high-density region 30a2, and a third high-density region 30a3. The first high-density region 30a1 is an example of a first region. Further, the second high-density region 30a2 is an example of a second region. Furthermore, the third high-density region 30a3 is an example of a fourth region.

At least one low-density region 30b includes a first low-density region 30b1 and a second low-density region 30b2. The first low-density region 30b1 is an example of a third region. The second low-density region 30b2 is an example of a fifth region.

Figure 2 is a schematic plan view of the connection layer of the first embodiment. Figure 2 shows the arrangement pattern of the high density regions 30a and low density regions 30b of the connection layer 30 in a plane parallel to the interface between the first superconducting layer 16 and the connection layer 30.

The length of the connection layer 30 in the first direction is shorter than the length of the connection layer 30 in the second direction. In other words, the first direction is the short side direction of the connection layer 30, and the second direction is the long side direction of the connection layer 30.

The first direction and the second direction are directions along the interface between the first superconducting layer 16 and the connection layer 30. Further, the second direction is a direction perpendicular to the first direction.

High-density regions 30a and low-density regions 30b are repeatedly arranged in the second direction. The low density region 30b is provided between the two high density regions 30a.

For example, the high density regions 30a are arranged at equal intervals in the second direction. Also, for example, the low density regions 30b are arranged at equal intervals in the second direction.

For example, the first low-density region 30b1 is provided between the first high-density region 30a1 and the second high-density region 30a2. Also, for example, the second low-density region 30b2 is provided between the second high-density region 30a2 and the third high-density region 30a3.

The low-density region 30b is exposed to the side surface 30s of the connection layer 30. For example, the first low-density region 30b1 is exposed to the side surface 30s of the connection layer 30. For example, the second low-density region 30b2 is exposed to the side surface of the connection layer 30.

Both ends of the low density region 30b in the first direction are exposed on the side surface 30s of the connection layer 30.

Both ends of the short side of the connection layer 30 in the low-density region 30b are exposed to the side surface 30s on the long side of the connection layer 30.

FIG. 1 is a cross section perpendicular to the interface between the first superconducting layer 16 and the connection layer 30. FIG. 1 is a cross section perpendicular to the first direction.

In a cross section perpendicular to the interface between the first superconducting layer 16 and the connection layer 30, the width of the low density region 30b in the direction parallel to the interface between the first superconducting layer 16 and the connection layer 30 is the same as that of the first high density region 30a. is smaller than the width in the direction parallel to the interface between the superconducting layer 16 and the connection layer 30. The width of the low density region 30b in the second direction is smaller than the width of the high density region 30a in the second direction.

For example, the third width w3 in the second direction of the first low-density region 30b1 is smaller than the first width w1 in the second direction of the first high-density region 30a1 and the second width w2 in the second direction of the second high-density region 30a2.

For example, the fifth width w5 in the second direction of the second low-density region 30b2 is smaller than the second width w2 in the second direction of the second high-density region 30a2 and the fourth width w4 in the second direction of the third high-density region 30a3.

In a cross section perpendicular to the interface between the first superconducting layer 16 and the connection layer 30, the width of the low-density region 30b in a direction parallel to the interface between the first superconducting layer 16 and the connection layer 30 is, for example, 5% to 50% of the width of the high-density region 30a in a direction parallel to the interface between the first superconducting layer 16 and the connection layer 30. The width of the low-density region 30b in the second direction is, for example, 5% to 50% of the width of the high-density region 30a in the second direction.

For example, the third width w3 in the second direction of the first low-density region 30b1 is 5% to 50% of the first width w1 in the second direction of the first high-density region 30a1 and the second width w2 in the second direction of the second high-density region 30a2.

For example, the fifth width w5 in the second direction of the second low-density region 30b2 is 5% to 50% of the second width w2 in the second direction of the second high-density region 30a2 and the fourth width w4 in the second direction of the third high-density region 30a3.

In a cross section perpendicular to the interface between the first superconducting layer 16 and the connection layer 30, the width of the low-density region 30b in a direction parallel to the interface between the first superconducting layer 16 and the connection layer 30 is, for example, 10 μm or more. The width of the low-density region 30b in the second direction is, for example, 10 μm or more.

In a cross section perpendicular to the interface between the first superconducting layer 16 and the connection layer 30, the width of the low-density region 30b in a direction parallel to the interface between the first superconducting layer 16 and the connection layer 30 is, for example, greater than the thickness of the connection layer 30 in a direction perpendicular to the interface between the first superconducting layer 16 and the connection layer 30. The width of the low-density region 30b in the second direction is, for example, greater than the thickness of the connection layer 30 in the direction from the first superconducting layer 16 toward the second superconducting layer 26.

FIG. 3 is an enlarged schematic cross-sectional view of a part of the connection layer of the first embodiment. FIG. 3 is a cross section perpendicular to the interface between the first superconducting layer 16 and the connection layer 30. FIG. 3 is a cross section including a part of the first high density region 30a1, a part of the second high density region 30a2, and the first low density region 30b1.

Connection layer 30 includes first crystal grains 31 , second crystal grains 32 , and holes 33 . The connection layer 30 is formed by sintering the first crystal grains 31 and the second crystal grains 32.

The first crystal grain 31 and the second crystal grain 32 are examples of crystal grains.

The connection layer 30 is, for example, porous. For example, voids 33 exist between particles included in the connection layer 30. The connection layer 30 does not need to have holes 33 .

The first crystal grains 31 contain rare earth elements (RE), barium (Ba), copper (Cu), and oxygen (O). The first crystal grains 31 are rare earth oxides. The first crystal grains 31 are, for example, single crystals or polycrystals having a perovskite structure.

The first crystal grains 31 have, for example, a chemical composition expressed as (RE)Ba ₂ Cu ₃ O _δ (RE is a rare earth element, 6≦δ≦7). The first crystal particles 31 are, for example, GdBa ₂ Cu ₃ O _δ (6≦δ≦7), YBa ₂ Cu ₃ O _δ (6≦δ≦7), or EuBa ₂ Cu ₃ O _δ (6≦δ≦ It has a chemical composition expressed as 7).

The first crystal grains 31 are superconductors.

The first crystal grains 31 have, for example, a plate shape or a flat shape. Flat shape means that the aspect ratio of the particles is 2 or more. The aspect ratio of a particle is the ratio of the major axis to the minor axis (major axis/minor axis) of the particle.

The median length of the first crystal grains 31 is, for example, 100 nm or more and 10 μm or less. The median value of the major axis of the first crystal grains 31 is, for example, larger than the thickness (t in FIG. 3) of the connection layer 30 in the direction from the first superconducting layer 16 to the second superconducting layer 26.

For example, the long axis direction of the first crystal grains 31 is inclined with respect to the interface between the first superconducting layer 16 and the connection layer 30. The angle of the long axis direction of the first crystal grain 31 with respect to the interface between the first superconducting layer 16 and the connection layer 30 is a first inclination angle. The first inclination angle is, for example, 15 degrees or more and 90 degrees or less.

The second crystal grains 32 contain rare earth elements (RE), barium (Ba), copper (Cu), and oxygen (O). The second crystal grains 32 are rare earth oxides. The second crystal grains 32 are, for example, single crystals or polycrystals having a perovskite structure. The second crystal grains 32 have, for example, a chemical composition expressed as (RE)Ba ₂ Cu ₃ O _δ (RE is a rare earth element, 6≦δ≦7).

The second crystal grains 32 are, for example, a superconductor.

The second crystal particles 32 contain, for example, the same rare earth element as the first crystal particles 31. The chemical composition of the second crystal particles 32 is, for example, the same as the chemical composition of the first crystal particles 31.

The second crystal grains 32 may contain a different rare earth element from the first crystal grains 31, for example. The chemical composition of the second crystal particles 32 may be different from the chemical composition of the first crystal particles 31, for example.

The second crystal particles 32 are, for example, spherical or irregular in shape. The aspect ratio of the second crystal particles 32 is, for example, less than 2.

The median length of the second crystal grains 32 is smaller than the median length of the first crystal grains 31 . The median length of the second crystal grains 32 is, for example, 10 nm or more and less than 1 μm.

The median length of the first crystal grains 31 is, for example, 10 times or more and 1000 times or less the median length of the second crystal grains 32.

FIG. 4 is a diagram showing definitions of the major axis and minor axis of the crystal grains of the first embodiment. FIG. 4 is a diagram illustrating the first crystal grain 31 as an example.

The major axis of a particle is the maximum length between any two points on the outer periphery of the particle. The short axis of a particle is the length of a line segment that passes through the midpoint of the line segment corresponding to the long axis, is perpendicular to the line segment, and has both ends at the outer periphery of the particle.

For example, the major axis of the first crystal grain 31 shown in FIG. 4 is the length of the line segment L1. Moreover, the short axis in the case of the first crystal grain 31 shown in FIG. 4 is the length of the line segment S1. Line segment S1 passes through midpoint M1 of line segment L1. The aspect ratio of the first crystal grains 31 shown in FIG. 4 is L1/S1.

FIG. 5 is a diagram showing the long axis distribution of crystal grains included in the connection layer of the first embodiment. FIG. 5 shows the long axis distribution of the first crystal grains 31 and the second crystal grains 32 included in the connection layer 30.

As shown in FIG. 5, the major axis distribution of the crystal particles contained in the connection layer 30 is a bimodal distribution. The bimodal distribution has a first distribution including a first peak (Pk1 in FIG. 5) and a second distribution including a second peak (Pk2 in FIG. 5). The major axis distribution of the crystal particles contained in the connection layer 30 has two peaks, the first peak Pk1 and the second peak Pk2.

The major axis corresponding to the first peak Pk1 is the first major axis (d1 in FIG. 5). The major axis corresponding to the second peak Pk2 is the second major axis (d2 in FIG. 5).

The first major axis d1 is larger than the second major axis d2. The first major axis d1 is, for example, 10 times or more and 1000 times or less the second major axis d2.

The first major axis d1 is, for example, 100 nm or more and 10 μm or less. The second major axis d2 is, for example, 10 nm or more and less than 1 μm.

The major axis distribution of the crystal particles contained in the connection layer 30 may be a multimodal distribution with two or more peaks.

As shown in FIG. 3, the high density region 30a includes crystal grains. The high density region 30a includes first crystal grains 31 and second crystal grains 32. For example, the first high density region 30a1 and the second high density region 30a2 include the first crystal grains 31 and the second crystal grains 32.

As shown in FIG. 3, the low density region 30b does not contain crystal grains. The low density region 30b does not include the first crystal grains 31 and the second crystal grains 32. For example, the first low density region 30b1 does not include the first crystal grains 31 and the second crystal grains 32.

The low density region 30b is, for example, an air gap 37 between the two high density regions 30a. For example, the first low-density region 30b1 is a gap 37 between the first high-density region 30a1 and the second high-density region 30a2.

As shown in FIG. 3, in a cross section perpendicular to the interface between the first superconducting layer 16 and the connection layer 30, the occupancy ratio of the crystal grains in the high density region 30a is greater than the occupancy ratio of the crystal grains in the low density region 30b. For example, the first occupancy ratio of the crystal grains in the first high density region 30a1 and the second occupancy ratio of the crystal grains in the second high density region 30a2 are greater than the third occupancy ratio of the crystal grains in the first low density region 30b1.

Furthermore, for example, the second occupancy ratio of crystal grains in the second high-density region 30a2 and the fourth occupancy ratio of crystal grains in the third high-density region 30a3 are It is larger than the fifth occupancy rate.

The crystal grain occupancy rate is the ratio of the area of the crystal grains to the cross-sectional area of each region in a cross section perpendicular to the interface between the first superconducting layer 16 and the connection layer 30. For example, it is also possible to use the ratio of the area of the crystal grains to a unit area in each region as the crystal grain occupancy rate.

Next, an example of a method for manufacturing the superconducting layer connection structure of the first embodiment will be described.

First, an oxide superconductor containing a rare earth element (RE), barium (Ba), copper (Cu), and oxygen (O) is formed. The following will explain the case where the rare earth element (RE) is gadolinium (Gd), but even if the rare earth element (RE) is an element other than gadolinium (Gd), the same method can be applied to the first embodiment. A connection structure of superconducting layers can be manufactured.

The oxide superconductor is formed, for example, by a solid phase reaction method. In forming an oxide superconductor, powders of Gd ₂ O ₃ , BaCO _{3 ,} and CuO are mixed and compressed to produce a green compact. By sintering the powder compact, an oxide superconductor having a composition of GdBa ₂ Cu ₃ O _δ (6≦δ≦7) is formed.

By crushing the oxide superconductor, first crystal particles 31 with an aspect ratio of 2 or more are formed. For example, by changing the degree and method of crushing, crystal particles with different aspect ratios and different major diameters can be formed.

Next, the connection layer 30 is formed using, for example, the MOD method.

An organometallic salt solution is prepared using powders of Gd(OCOCH ₃ ) ₂ , Ba(OCOCH ₃ ) ₂ , and Cu(OCOCH ₃ ) _2. The prepared organometallic salt solution is mixed with first crystal particles to prepare a slurry.

Next, the slurry is applied onto the first superconducting layer 16. When applying the slurry onto the first superconducting layer 16, areas where the slurry is applied and areas where the slurry is not applied are alternately created.

After that, a first heat treatment is performed in an oxygen atmosphere. The first heat treatment is performed, for example, at a temperature of 400° C. or higher and 600° C. or lower. The slurry is pre-baked by the first heat treatment, and a connection layer film is formed.

As an alternative method, the slurry may be applied to the entire surface of the first superconducting layer 16, and then the first heat treatment described above may be performed to form a connection layer film. The connection layer film thus formed is then scraped off to obtain the desired shape of the third region. For example, the connection layer film may be physically peeled off using a cotton swab or the like.

Next, the connection layer film is sandwiched between the first superconducting layer 16 and the second superconducting layer 26 and pressurized. With the connection layer film under pressure, a second heat treatment is performed in an air atmosphere. The second heat treatment is performed at a temperature of, for example, 700°C or higher and 900°C or lower.

Next, a third heat treatment is performed in an oxygen atmosphere. The third heat treatment is performed, for example, at a temperature of 400°C or higher and 600°C or lower. The third heat treatment performs the main firing of the connection layer film, and the connection layer 30 is formed.

By firing the slurry, second crystal grains 32 are formed. The major axis of the second crystal grain 32 is smaller than the major axis of the first crystal grain 31 .

The region to which the slurry is applied between the first superconducting layer 16 and the second superconducting layer 26 becomes a high-density region 30a containing first crystal grains 31 and second crystal grains 32. Further, a region between the first superconducting layer 16 and the second superconducting layer 26 to which the slurry is not applied becomes a low-density region 30b that does not include the first crystal grains 31 and the second crystal grains 32.

By the above method, the first superconducting layer 16 and the second superconducting layer 26 are connected. By the above method, the superconducting layer connection structure 100 of the first embodiment is manufactured.

Next, we will explain the function of the superconducting layer connection structure of the first embodiment.

For example, in a nuclear magnetic resonance apparatus (NMR) or a magnetic resonance imaging apparatus (MRI), a superconducting coil is used to generate a strong magnetic field. A superconducting coil is formed by winding a superconducting wire around a winding frame.

To make superconducting wire longer, for example, multiple superconducting wires are connected. For example, the ends of two superconducting wires are connected using a connection structure. The connection structure for connecting superconducting wires is required to have low electrical resistance and high mechanical strength.

The connection layer 30 of the connection structure 100 of the superconducting layers of the first embodiment includes a low-density region 30b that does not contain crystal grains. The region that becomes the low-density region 30b is exposed to the side of the slurry when the connection layer 30 is formed by firing, and is not coated with the slurry, so that it can function as an oxygen supply path.
Therefore, oxygen can be sufficiently supplied to the slurry even in an area inside the slurry that is far from the side surface of the slurry that is exposed to the atmosphere.
By supplying a sufficient amount of oxygen to the crystal grains in the connection layer, there is no _shortage of oxygen in the crystal grains having a chemical composition expressed by, for example, ( _RE ) _Ba2Cu3Oδ (RE is a rare earth element, 6≦δ≦7), and therefore the electrical resistance of the connection layer can be reduced.
Furthermore, by supplying a sufficient amount of oxygen to the slurry, the bonds between the crystal grains in the connection layer can be strengthened, and therefore the mechanical strength of the connection layer can be increased.

In a cross section perpendicular to the interface between the first superconducting layer 16 and the connection layer 30, it is preferable that the width of the low-density region 30b in a direction parallel to the interface between the first superconducting layer 16 and the connection layer 30 is smaller than the width of the high-density region 30a in a direction parallel to the interface between the first superconducting layer 16 and the connection layer 30.
By making the width relationship between the high density region and the low density region such that the high density region is larger than the low density region, it is possible to suppress the electrical resistance while increasing the mechanical strength. If the width of the low density region 30b where no crystal grains exist is increased, the electrical resistance of the connection layer 30 may increase. Also, if the width of the low density region 30b where no crystal grains exist is increased, the mechanical strength of the connection layer 30 may decrease.

From the viewpoint of reducing the electrical resistance of the connection layer 30 and increasing the mechanical strength of the connection layer 30, in a cross section perpendicular to the interface between the first superconducting layer 16 and the connection layer 30, the width of the low-density region 30b in a direction parallel to the interface between the first superconducting layer 16 and the connection layer 30 is preferably 50% or less, more preferably 30% or less, and even more preferably 10% or less of the width of the high-density region 30a in a direction parallel to the interface between the first superconducting layer 16 and the connection layer 30.

It is preferable that the low-density region 30b is exposed on the side surface of the long side of the connection layer 30. In other words, it is preferable that the end of the low-density region 30b in the direction in which the short side of the connection layer 30 extends is exposed on the side surface of the connection layer 30. Since the distance of the oxygen supply path from the side surface of the connection layer 30 can be shortened, the efficiency of oxygen supply to the inside of the slurry is increased. This reduces the electrical resistance of the connection layer 30 and increases its mechanical strength.

As shown in FIG. 5, in the superconducting layer connection structure 100 of the first embodiment, the grain size distribution of crystal grains included in the high-density region 30a of the connection layer 30 includes a bimodal distribution. Since the connection structure 100 includes the first crystal grains 31 having a large grain size, the crystal grain interfaces occupied in the connection layer 30 are reduced. Therefore, the interfacial resistance at the crystal grain interface is suppressed from increasing the electrical resistance of the connection layer 30. Therefore, the electrical resistance of the connection structure 100 becomes low.

Furthermore, in the superconducting layer connection structure 100 of the first embodiment, the second crystal grains 32 having a small grain size fill the spaces between the first crystal grains 31 having a large grain size. The presence of the second crystal grains 32 increases the bonding strength between the first crystal grains 31. Therefore, the mechanical strength of the connection layer 30 becomes high, and the mechanical strength of the connection structure 100 becomes high.

Here, regarding the connection layer of the superconducting layer of the first embodiment, a method of measuring the occupation ratio of crystal grains, the width and length of the first region, etc. will be explained.

<Occupancy ratio of crystal particles>
The occupancy rate of crystal particles is measured, for example, as follows.

First, a cross-section of a plane perpendicular to the interface between the first superconducting layer 16 and the connection layer 30 and including the first region, second region, and third region of the connection layer 30 is imaged using a SEM. The cross section to be imaged with the SEM is cut out from the connection layer using, for example, a focused ion beam. The magnification when imaging with SEM is, for example, 2,000 times or more and 10,000 times or less.

For example, five cross sections are obtained from one connection layer 30. Regions such as particles and resin can be determined from the contrast from the SEM image. At each location, the occupation ratio of crystal grains in the first region, second region, and third region is determined. Specifically, the occupancy ratio of each area can be determined using commercially available image analysis software such as ImageJ.

The obtained occupancy ratios for each region are averaged. The obtained average values are regarded as the occupancy ratios for each region of the connection layer 30.

<Measurement of area width and length>
The widths of regions such as the first region, second region, and third region are measured as follows.

First, a cross section of the surface perpendicular to the interface between the first superconducting layer 16 and the connection layer 30 and including the first region, the second region, and the third region of the connection layer 30 is imaged by an SEM. The cross section imaged by the SEM is cut out from the connection layer using, for example, a focused ion beam. The magnification when imaging by the SEM is, for example, 2,000 times or more and 10,000 times or less.

For example, five cross sections are obtained from one connection layer 30. The widths of the first region, second region, and third region are measured at each location.

<Measurement of area length>
The lengths of regions such as the first region, second region, and third region are measured as follows.

First, the second superconducting layer 26 and the like on the connection layer 30 are removed. The second superconducting layer 26 and the like are removed by, for example, a mechanical polishing method. The exposed upper surface of the connection layer 30 is imaged using a SEM. The magnification when imaging with SEM is, for example, 100 times or more and 1,000 times or less.

The length of each region in the short side direction of the connection layer 30 and the length in the long side direction of the connection layer 30 is measured. The length of each region can be measured on the SEM image.

The other fourth and fifth regions are also measured in the same manner.

(First modification)
The connection structure of the first modification of the first embodiment differs from the connection structure of the first embodiment in that the third region includes resin.

FIG. 6 is an enlarged schematic cross-sectional view of a part of the connection layer of the first modification of the first embodiment. FIG. 6 is a diagram corresponding to FIG. 3.

In the connection layer 30 of the connection structure of the first modified example, the low-density region 30b contains resin 36. The resin 36 contains voids 37. For example, after the connection layer 30 is formed, the resin 36 is formed in the low-density region 30b by an impregnation method. The resin 36 is, for example, an epoxy resin.

The connection structure of the first modified example has high mechanical strength because the connection layer 30 contains resin 36.

(Second modification)
FIG. 7 is a schematic plan view of a connection layer of a second modification of the first embodiment. FIG. 7 is a diagram corresponding to FIG. 2.

In the second modified connection layer 30, the low-density region 30b extends in the second direction. In the second modified connection layer 30, the low-density region 30b extends in the long side direction of the connection layer 30.

(Third Modification)
8 is a schematic plan view of a connection layer according to a third modified example of the first embodiment, and corresponds to FIG.

In the third modified connection layer 30, the low-density region 30b extends in the first direction and the second direction. In the third modified connection layer 30, the low-density region 30b extends in the short side direction and the long side direction of the connection layer 30.

(Fourth modification)
FIG. 9 is a schematic plan view of the connection layer of the fourth modification of the first embodiment. FIG. 9 is a diagram corresponding to FIG. 2.

In the fourth modified example, the connection layer 30 has low-density regions 30b extending in a first direction, and only one end in the first direction is exposed on the side of the connection layer 30. In the fourth modified example, the connection layer 30 has low-density regions 30b extending in the short side direction of the connection layer 30, and only one end in the short side direction of the connection layer 30 is exposed on the side of the connection layer 30. For example, the low-density regions 30b are arranged alternately with one end exposed and the other end exposed.

(Fifth modification)
FIG. 10 is a schematic plan view of the connection layer of the fifth modification of the first embodiment. FIG. 10 is a diagram corresponding to FIG. 2.

In the fifth modified example, the connection layer 30 has low-density regions 30b extending in a direction that intersects obliquely with both the first and second directions. In the third modified example, the connection layer 30 has low-density regions 30b extending in a direction that intersects obliquely with both the short side direction and the long side direction of the connection layer 30.

As described above, the superconducting layer connection structure and modification of the first embodiment are provided between the first superconducting layer, the second superconducting layer, the first superconducting layer and the second superconducting layer, a connection layer containing crystal particles containing rare earth elements (RE), barium (Ba), copper (Cu), and oxygen (O), the connection layer comprising a first region, a second region and , a third region provided between the first region and the second region, the first region and the second region contain crystal grains, and the third region contains crystal grains. The third region is exposed on the side surface of the connection layer, is perpendicular to the interface between the first superconducting layer and the connection layer, and includes the first region, the second region, and the third region. In the cross section, a first occupancy ratio of crystal grains in the first region and a second occupancy ratio of crystal grains in the second region are larger than a third occupancy ratio of crystal grains in the third region. It is a layer connection structure. With this structure, oxygen can be obtained from the third region, so that the unreacted region of crystal particles in the center of the connection layer can be reduced. Therefore, low electrical resistance and high mechanical strength can be achieved.

Second Embodiment
The connection structure of the superconducting layers of the second embodiment differs from the connection structure of the superconducting layers of the first embodiment in that the third region includes crystal grains. Hereinafter, some of the contents that overlap with the first embodiment may be omitted.

Figure 11 is an enlarged schematic cross-sectional view of a portion of the connection layer of the second embodiment. Figure 3 is a cross section perpendicular to the interface between the first superconducting layer 16 and the connection layer 30. Figure 11 is a cross section including a portion of the first high-density region 30a1, a portion of the second high-density region 30a2, and the first low-density region 30b1. Figure 11 corresponds to Figure 3 of the first embodiment.

Connection layer 30 includes first crystal grains 31 , second crystal grains 32 , and holes 33 . The connection layer 30 is formed by sintering the first crystal grains 31 and the second crystal grains 32.

The first crystal particle 31 and the second crystal particle 32 are examples of crystal particles.

The length distribution of the crystal grains included in the connection layer 30 is a bimodal distribution. A bimodal distribution has a first distribution that includes a first peak and a second distribution that includes a second peak. The long diameter distribution of the crystal grains included in the connection layer 30 has two peaks, a first peak and a second peak.

As shown in FIG. 11, the high density region 30a includes crystal grains. The high density region 30a includes first crystal grains 31 and second crystal grains 32. For example, the first high density region 30a1 and the second high density region 30a2 include the first crystal grains 31 and the second crystal grains 32.

The length distribution of crystal grains included in the high-density region 30a has two peaks, a first peak and a second peak. The length distribution of crystal grains included in the high-density region 30a is a bimodal distribution.

As shown in FIG. 11, the low density region 30b includes crystal grains. Low density region 30b includes first crystal grains 31 and second crystal grains 32. For example, the first low density region 30b1 and the second low density region 30b2 include first crystal grains 31 and second crystal grains 32.

The major axis distribution of the crystal particles contained in the low-density region 30b has two peaks, a first peak and a second peak. The major axis distribution of the crystal particles contained in the low-density region 30b is a bimodal distribution.

The first crystal grains 31 have, for example, a plate shape or a flat shape.

As shown in FIG. 11, in a cross section perpendicular to the interface between the first superconducting layer 16 and the connection layer 30, the occupation ratio of crystal grains in the high-density region 30a is higher than the occupation ratio of crystal grains in the low-density region 30b. big. For example, the first occupancy ratio of crystal grains in the first high-density region 30a1 and the second occupancy ratio of crystal grains in the second high-density region 30a2 are It is larger than the third occupancy rate.

In a cross section perpendicular to the interface between the first superconducting layer 16 and the connection layer 30, the occupancy ratio of the crystal grains in the low-density region 30b is, for example, 10% to 50% of the occupancy ratio of the crystal grains in the high-density region 30a. For example, the third occupancy ratio of the crystal grains in the first low-density region 30b1 is 10% to 50% of the first occupancy ratio of the crystal grains in the first high-density region 30a1 and the second occupancy ratio of the crystal grains in the second high-density region 30a2.

For example, the proportion of the second crystal grains 32 contained in the low-density region 30b is smaller than the proportion of the second crystal grains 32 contained in the high-density region 30a.

For example, the average long diameter of the crystal particles contained in the low-density region 30b is larger than the average long diameter of the crystal particles contained in the high-density region 30a. For example, the average long diameter of the crystal particles contained in the first low-density region 30b1 is larger than the average long diameter of the crystal particles contained in the first high-density region 30a1. The crystal particles contained in the low-density region 30b have a higher proportion of particles with a large long diameter, for example, compared to the high-density region 30a.

Next, an example of a method for manufacturing the superconducting layer connection structure of the second embodiment will be described.

First, an oxide superconductor containing a rare earth element (RE), barium (Ba), copper (Cu), and oxygen (O) is formed.

The oxide superconductor is formed, for example, by _a solid-state reaction method. In forming the oxide superconductor, powders of _Gd2O3 , BaCO3 _, and CuO are mixed and compressed to produce a _green compact. The _green compact is sintered to form an oxide superconductor having a composition of _GdBa2Cu3Oδ (6≦δ≦7).

By crushing the oxide superconductor, first crystal particles 31 with an aspect ratio of 2 or more are formed. For example, by changing the degree and method of crushing, crystal particles with different aspect ratios and different major diameters can be formed.

Next, the connection layer 30 is formed using, for example, the MOD method.

An organometallic salt solution is prepared using powders of Gd( _OCOCH3 ) ₂ , Ba( _OCOCH3 ) ₂ , and Cu( _OCOCH3 ) ₂ . The prepared organometallic salt solution is mixed with first crystal particles to prepare a slurry. At this time, a first slurry using an organometallic salt solution with a high organometallic salt concentration and a second slurry using an organometallic salt solution with a low organometallic salt concentration are prepared.

Next, the slurry is applied onto the first superconducting layer 16. When applying the slurry onto the first superconducting layer 16, areas where the first slurry is applied and areas where the second slurry is applied are alternately created.

Then, a first heat treatment is performed in an oxygen atmosphere. The first heat treatment is performed, for example, at a temperature of 400°C or higher and 600°C or lower. The first heat treatment pre-calcines the slurry, forming a film of the connection layer.

Next, the connection layer film is sandwiched between the first superconducting layer 16 and the second superconducting layer 26 and pressurized. With the connection layer film under pressure, a second heat treatment is performed in an air atmosphere. The second heat treatment is performed at a temperature of, for example, 700°C or higher and 900°C or lower.

Next, a third heat treatment is performed in an oxygen atmosphere. The third heat treatment is performed, for example, at a temperature of 400° C. or higher and 600° C. or lower. Through the third heat treatment, the main firing of the connection layer film is performed, and the connection layer 30 is formed.

By firing the slurry, second crystal grains 32 are formed. The major axis of the second crystal grain 32 is smaller than the major axis of the first crystal grain 31 .

The region to which the first slurry is applied between the first superconducting layer 16 and the second superconducting layer 26 becomes a high-density region 30a containing first crystal grains 31 and second crystal grains 32. Further, between the first superconducting layer 16 and the second superconducting layer 26, the region coated with the second slurry includes the first crystal particles 31 and the second crystal particles 32, and the second This results in a low-density region 30b in which the proportion of crystal grains 32 occupied is small.

By the above method, the first superconducting layer 16 and the second superconducting layer 26 are connected. By the above method, the superconducting layer connection structure of the second embodiment is manufactured.

Next, we will explain the function of the superconducting layer connection structure of the second embodiment.

The connection layer 30 of the superconducting layer connection structure of the second embodiment has a low-density region 30b in which the proportion of crystal grains is small. The region that becomes the low-density region 30b is exposed to the side of the slurry when the connection layer 30 is formed by firing, and since the slurry solution has a low concentration and the amount of second crystal grains 32 formed is small, there are many voids, which can function as an oxygen supply path.

Therefore, when forming the connection layer 30 by firing, a sufficient amount of oxygen can be supplied to the slurry that will become the connection layer 30. Therefore, the electrical resistance of the connection layer 30 becomes low and the mechanical strength becomes high.

In addition, since the low-density region 30b contains crystal particles, it is possible to pass a current through the low-density region 30b. This further reduces the electrical resistance of the connection layer 30.

In addition, the low-density region 30b contains crystal particles, which increases the mechanical strength of the low-density region 30b. Therefore, the mechanical strength of the connection layer 30 is increased.

The average long diameter of the crystal particles contained in the low-density region 30b is preferably larger than the average long diameter of the crystal particles contained in the high-density region 30a. By increasing the proportion of the first crystal particles 31 that mainly function as current paths among the crystal particles contained in the low-density region 30b, the electrical resistance of the connection layer 30 can be reduced.

In a cross section perpendicular to the interface between the first superconducting layer 16 and the connection layer 30, the occupation ratio of crystal grains in the low density region 30b is 10% or more and no more than 50% of the occupation ratio of crystal grains in the high density region 30a. It is preferable that there be. By exceeding the above lower limit, the electrical resistance of the low-density region 30b becomes low, and the electrical resistance of the connection layer 30 can be reduced. By exceeding the above lower limit, the mechanical strength of the connection layer 30 can be increased. Moreover, by being less than the above upper limit, the function as an oxygen supply path when forming the connection layer 30 can be improved.

As described above, according to the connection structure and modified example of the superconducting layer of the second embodiment, the presence of crystal grains in the low-density region of the connection layer makes it possible to achieve lower electrical resistance and high mechanical strength.

Third Embodiment
The superconducting layer connection structure of the third embodiment differs from the superconducting layer connection structure of the first embodiment in that the distribution of the major axes of the crystal grains contained in the first region has three peaks, the third region contains crystal grains, and the distribution of the major axes of the crystal grains contained in the third region has two peaks. Also, the superconducting layer connection structure of the second embodiment differs from the superconducting layer connection structure of the second embodiment in that the distribution of the major axes of the crystal grains contained in the first region has three peaks. Hereinafter, some of the contents that overlap with the first and second embodiments may be omitted.

FIG. 12 is an enlarged schematic cross-sectional view of a part of the connection layer of the third embodiment. FIG. 12 is a cross section perpendicular to the interface between the first superconducting layer 16 and the connection layer 30. FIG. 12 is a cross section including a part of the first high density region 30a1, a part of the second high density region 30a2, and the first low density region 30b1. FIG. 12 corresponds to FIG. 3 of the first embodiment and FIG. 11 of the second embodiment.

The connection layer 30 of the third embodiment includes first crystal grains 31 , second crystal grains 32 , third crystal grains 34 , and holes 33 . The connection layer 30 is formed by sintering first crystal grains 31, second crystal grains 32, and third crystal grains 34.

The connection layer 30 of the third embodiment differs from the connection layer 30 of the first embodiment and the connection layer 30 of the second embodiment in that it includes third crystal particles 34.

The first crystal particle 31, the second crystal particle 32, and the third crystal particle 34 are examples of crystal particles.

The third crystal particles 34 contain a rare earth element (RE), barium (Ba), copper (Cu), and oxygen (O). The third crystal particles 34 are rare earth oxides. The third crystal particles 34 are, for example, single crystals or polycrystals having a perovskite structure. The third crystal particles 34 have a chemical composition represented, for example, by (RE)Ba ₂ Cu ₃ O _δ (RE is a rare earth element, 6≦δ≦7).

The third crystal grain 34 is a superconductor.

The third crystal grains 34 contain the same rare earth element as the first crystal grains 31, for example. The chemical composition of the third crystal grains 34 is, for example, the same as the chemical composition of the first crystal grains 31.

The third crystal particles 34 may, for example, contain a rare earth element different from that of the first crystal particles 31. The chemical composition of the third crystal particles 34 may, for example, be different from that of the first crystal particles 31.

The third crystal particle 34 has, for example, an irregular shape. The aspect ratio of the third crystal particle 34 is smaller than the aspect ratio of the first crystal particle 31. The aspect ratio of the third crystal particle 34 is, for example, less than 2.

The median long diameter of the third crystal particles 34 is smaller than the long diameter of the first crystal particles 31. The median long diameter of the third crystal particles 34 is, for example, 50 nm or more and less than 5 μm. The median long diameter of the third crystal particles 34 is, for example, smaller than the thickness (t in FIG. 12) of the connection layer 30 in the direction from the first superconducting layer 16 to the second superconducting layer 26.

FIG. 13 is a diagram showing the long axis distribution of crystal grains included in the connection layer of the third embodiment. FIG. 13 shows the length axis distribution of the first crystal grains 31, second crystal grains 32, and third crystal grains 34 included in the connection layer 30.

As shown in FIG. 13, the length distribution of crystal grains included in the connection layer 30 has a trimodal distribution. The trimodal distribution includes a first distribution including a first peak (Pk1 in FIG. 13), a second distribution including a second peak (Pk2 in FIG. 13), and a third peak (Pk2 in FIG. 13). It has a third distribution including Pk3). The length diameter distribution of the crystal grains included in the connection layer 30 has three peaks: a first peak Pk1, a second peak Pk2, and a third peak Pk3.

The major axis distribution of the crystal particles contained in the connection layer 30 may be a multimodal distribution with four or more peaks.

The major axis corresponding to the first peak Pk1 is the first major axis (d1 in FIG. 13). The major axis corresponding to the second peak Pk2 is the second major axis (d2 in FIG. 13). The major axis corresponding to the third peak Pk3 is the third major axis (d3 in FIG. 13).

The first major diameter d1 is larger than the third major diameter d3. The second major diameter d2 is smaller than the third major diameter d3. The first major diameter d1 is, for example, 10 times or more and 1000 times or less than the second major diameter d2. The third major diameter d3 is, for example, 10 times or more and 1000 times or less than the second major diameter d2.

The first major diameter d1 is, for example, 100 nm or more and 10 μm or less. The third major diameter d3 is, for example, 50 nm or more and 5 μm or less. The second major diameter d2 is, for example, 10 nm or more and less than 1 μm.

The crystal particles contained in the first distribution are mainly first crystal particles 31. The crystal particles contained in the second distribution are mainly second crystal particles 32. The crystal particles contained in the third distribution are mainly third crystal particles 34.

As shown in FIG. 12, the high density region 30a includes crystal grains. The high density region 30a includes first crystal grains 31, second crystal grains 32, and third crystal grains 34. For example, the first high density region 30a1 and the second high density region 30a2 include the first crystal grains 31, second crystal grains 32, and third crystal grains 34.

The length distribution of crystal grains included in the high-density region 30a has three peaks: a first peak, a second peak, and a third peak. The length distribution of crystal grains included in the high-density region 30a is a trimodal distribution.

As shown in FIG. 12, the low-density region 30b includes crystal grains. The low-density region 30b includes first crystal grains 31 and second crystal grains 32. For example, the first low-density region 30b1 and the second low-density region 30b2 include the first crystal grains 31 and the second crystal grains 32.

Low density region 30b does not include third crystal grains 34.

The major axis distribution of the crystal particles contained in the low-density region 30b has two peaks, a first peak and a second peak. The major axis distribution of the crystal particles contained in the low-density region 30b is a bimodal distribution.

The first crystal grains 31 have, for example, a plate shape or a flat shape.

As shown in FIG. 12, in a cross section perpendicular to the interface between the first superconducting layer 16 and the connection layer 30, the occupation ratio of crystal grains in the high-density region 30a is higher than the occupation ratio of crystal grains in the low-density region 30b. big. For example, the first occupancy ratio of crystal grains in the first high-density region 30a1 and the second occupancy ratio of crystal grains in the second high-density region 30a2 are It is larger than the third occupancy rate.

In a cross section perpendicular to the interface between the first superconducting layer 16 and the connection layer 30, the occupancy rate of the crystal grains in the low-density region 30b is, for example, 10% to 50% of the occupancy rate of the crystal grains in the high-density region 30a. For example, the third occupancy rate of the crystal grains in the first low-density region 30b1 is 10% to 50% of the first occupancy rate of the crystal grains in the first high-density region 30a1 and the second occupancy rate of the crystal grains in the second high-density region 30a2.

For example, the proportion of the second crystal grains 32 contained in the low-density region 30b is smaller than the proportion of the second crystal grains 32 contained in the high-density region 30a.

For example, the average long diameter of the crystal particles contained in the low-density region 30b is larger than the average long diameter of the crystal particles contained in the high-density region 30a. For example, the average long diameter of the crystal particles contained in the first low-density region 30b1 is larger than the average long diameter of the crystal particles contained in the first high-density region 30a1.

Next, an example of a method for manufacturing a superconducting layer connection structure according to the third embodiment will be described.

First, an oxide superconductor is formed that contains rare earth elements (RE), barium (Ba), copper (Cu), and oxygen (O).

The oxide superconductor is formed, for example, by _a solid-state reaction method. In forming the oxide superconductor, powders of _Gd2O3 , BaCO3 _, and CuO are mixed and compressed to produce a _green compact. The _green compact is sintered to form an oxide superconductor having a composition of _GdBa2Cu3Oδ (6≦δ≦7).

By crushing the oxide superconductor, first crystal particles 31 having an aspect ratio of 2 or more are formed. Further, by pulverizing the oxide superconductor, third crystal particles 34 having an aspect ratio of less than 2 and a longer axis smaller than the first crystal particles 31 are formed. For example, by changing the degree and method of crushing, crystal particles with different aspect ratios and different lengths can be formed.

Next, the connection layer 30 is formed, for example, using the MOD method.

An organic metal salt solution is prepared using powders of Gd(OCOCH ₃ ) ₂ , Ba(OCOCH ₃ ) ₂ , and Cu(OCOCH ₃ ) ₂ . The first crystal particles 31 and the third crystal particles 34 are mixed with the prepared organic metal salt solution to prepare a first slurry. Further, a second slurry is prepared by mixing only the first crystal particles 31 into the prepared organic metal salt solution.

Next, the slurry is applied onto the first superconducting layer 16. When applying the slurry onto the first superconducting layer 16, areas where the first slurry is applied and areas where the second slurry is applied are alternately created.

After that, a first heat treatment is performed in an oxygen atmosphere. The first heat treatment is performed, for example, at a temperature of 400° C. or higher and 600° C. or lower. The slurry is pre-baked by the first heat treatment, and a connection layer film is formed.

Next, the connection layer film is sandwiched between the first superconducting layer 16 and the second superconducting layer 26 and pressurized. With the connection layer film under pressure, a second heat treatment is performed in an air atmosphere. The second heat treatment is performed at a temperature of, for example, 700°C or higher and 900°C or lower.

Next, a third heat treatment is performed in an oxygen atmosphere. The third heat treatment is performed, for example, at a temperature of 400°C or higher and 600°C or lower. The third heat treatment performs the main firing of the connection layer film, and the connection layer 30 is formed.

By firing the slurry, second crystal grains 32 are formed. The major axis of the second crystal grain 32 is smaller than the major axis of the first crystal grain 31 . The major axis of the second crystal grain 32 is smaller than the major axis of the third crystal grain 34.

The area between the first superconducting layer 16 and the second superconducting layer 26 where the first slurry is applied becomes a high-density area 30a that includes the first crystal particles 31, the second crystal particles 32, and the third crystal particles 34. Also, the area between the first superconducting layer 16 and the second superconducting layer 26 where the second slurry is applied becomes a low-density area 30b that includes the first crystal particles 31 and the second crystal particles 32, but does not include the third crystal particles 34.

By the above method, the first superconducting layer 16 and the second superconducting layer 26 are connected. By the above method, the superconducting layer connection structure of the third embodiment is manufactured.

Next, we will explain the function and effect of the superconducting layer connection structure of the third embodiment.

The connection layer 30 of the superconducting layer connection structure of the third embodiment includes a low-density region 30b in which the proportion of crystal grains occupied is small. The region that becomes the low-density region 30b is exposed on the side surface of the slurry when the connection layer 30 is formed by firing, exists in the short side direction, that is, has the depth, and does not contain the third crystal grains 34. , there are many voids and can function as an oxygen supply path.

Therefore, when forming the connection layer 30 by firing, a sufficient amount of oxygen can be supplied to the slurry that will become the connection layer 30. Therefore, the electrical resistance of the connection layer 30 can be lowered, and the mechanical strength can be increased.

In addition, since the low-density region 30b contains crystal particles, it is possible to pass a current through the low-density region 30b. This makes it possible to further reduce the electrical resistance of the connection layer 30.

In addition, since the low-density region 30b contains crystal particles, the mechanical strength of the low-density region 30b can be increased. Therefore, the mechanical strength of the connection layer 30 can be increased.

The average long diameter of the crystal particles contained in the low-density region 30b is preferably larger than the average long diameter of the crystal particles contained in the high-density region 30a. By increasing the proportion of the first crystal particles 31 that mainly function as current paths among the crystal particles contained in the low-density region 30b, the electrical resistance of the connection layer 30 can be reduced.

In a cross section perpendicular to the interface between the first superconducting layer 16 and the connection layer 30, the occupation ratio of crystal grains in the low density region 30b is 10% or more and no more than 50% of the occupation ratio of crystal grains in the high density region 30a. It is preferable that there be. By exceeding the above lower limit of 10%, the electrical resistance of the low density region 30b can be lowered, and the electrical resistance of the connection layer 30 can be lowered. By exceeding the above lower limit, the mechanical strength of the connection layer 30 can be increased. Moreover, by being less than the above upper limit, the function as an oxygen supply path when forming the connection layer 30 can be improved.

The connection layer 30 of the third embodiment includes third crystal grains 34 whose aspect ratio is smaller than the first crystal grains 31 and whose major axis is larger than the second crystal grains 32. When applying the first slurry onto the first superconducting layer 16 to form the connection layer 30, the first slurry includes third crystal particles 34 in addition to the first crystal particles 31.

By including the third crystal particles 34 in the first slurry, the first crystal particles 31 tend to be arranged with their major axes inclined to the surface of the first superconducting layer 16. As a result, as shown in FIG. 12, the major axes of the first crystal particles 31 tend to be arranged in a direction inclined to the interface between the first superconducting layer 16 and the connection layer 30.

In other words, the first inclination angle of the long axis direction of the first crystal grains 31 with respect to the interface between the first superconducting layer 16 and the connection layer 30 becomes large. The first inclination angle is, for example, 15 degrees or more and 90 degrees or less.

The long axis direction of the first crystal grains 31 is a direction in which current easily flows. When the long axis direction of the first crystal grains 31 is inclined with respect to the interface between the first superconducting layer 16 and the connection layer 30, the current flowing through the connection layer 30 mainly flows in the long axis direction of the first crystal grains 31. It will flow to Therefore, the electrical resistance of the connection layer 30 becomes low.

Furthermore, when the long axis direction of the first crystal grains 31 is inclined with respect to the interface between the first superconducting layer 16 and the connection layer 30, the proportion of the crystal grain interface in the path of the current flowing through the connection layer 30 is reduced. Therefore, the electrical resistance of the connection layer 30 can be lowered.

In the superconducting layer connection structure of the third embodiment, the connection layer 30 includes the third crystal grains 34, so that the electrical resistance can be lowered.

As described above, according to the superconducting layer connection structure and modification of the third embodiment, in the cross section perpendicular to the interface between the first superconducting layer and the connection layer, the first occupation ratio of crystal grains in the first region is and a second occupancy ratio of the crystal grains in the second region is larger than a third occupancy ratio of the crystal grains in the third region, and the third region is a portion of the superconducting layer exposed on the side surface of the connection layer. It has a connection structure. With this structure, oxygen can be obtained from the third region, so that the unreacted region of crystal particles in the center of the connection layer can be reduced. Therefore, low electrical resistance and high mechanical strength can be achieved.

Fourth Embodiment
A superconducting wire according to a fourth embodiment includes a first superconducting wire including a first superconducting layer, a second superconducting wire including a second superconducting layer, a third superconducting layer, and connection layers provided between the first superconducting layer and the third superconducting layer and between the second superconducting layer and the third superconducting layer, the connection layers including crystal grains including a rare earth element (RE), barium (Ba), copper (Cu), and oxygen (O), and the distribution of the major axis of the crystal grains has at least two peaks. The connection layers between the first superconducting layer and the third superconducting layer include: The fourth embodiment of the superconducting wire includes a first region, a second region, and a third region provided between the first region and the second region, the first region and the second region include crystal grains, the third region includes or does not include crystal grains, and the third region is exposed to a side surface of the connection layer, and in a cross section perpendicular to the interface between the first superconducting layer and the connection layer and including the first region, the second region, and the third region, the first occupancy ratio of the crystal grains in the first region and the second occupancy ratio of the crystal grains in the second region are greater than the third occupancy ratio of the crystal grains in the third region. The fourth embodiment of the superconducting wire uses the connection structure of the superconducting layer of the first embodiment as a structure for connecting the first superconducting wire and the second superconducting wire. Hereinafter, some of the contents that overlap with the first embodiment will be omitted.

Figure 14 is a schematic cross-sectional view of a superconducting wire of the fourth embodiment. The superconducting wire 400 of the fourth embodiment includes a first superconducting wire 401, a second superconducting wire 402, and a connecting member 403. The superconducting wire 400 of the fourth embodiment is elongated by connecting the first superconducting wire 401 and the second superconducting wire 402 using the connecting member 403.

The first superconducting wire 401 comprises a first substrate 12, a first intermediate layer 14, a first superconducting layer 16, and a first protective layer 18. The second superconducting wire 402 comprises a second substrate 22, a second intermediate layer 24, a second superconducting layer 26, and a second protective layer 28. The connecting member 403 comprises a third substrate 42, a third intermediate layer 44, and a third superconducting layer 46.

The first superconducting wire 401, the second superconducting wire 402, and the connecting member 403 have a structure similar to that of the first superconducting member 10 and the second superconducting member 20 of the first embodiment.

Connection layer 30 is provided between first superconducting layer 16 and third superconducting layer 46 . Connection layer 30 is in contact with first superconducting layer 16 . Connection layer 30 is in contact with third superconducting layer 46 .

The connection layer 30 is provided between the second superconducting layer 26 and the third superconducting layer 46. The connection layer 30 contacts the second superconducting layer 26. The connection layer 30 contacts the third superconducting layer 46.

The connection layer 30 between the first superconducting layer 16 and the third superconducting layer 46 and the connection layer 30 between the second superconducting layer 26 and the third superconducting layer 46 are continuous.

The connection layer 30 does not exist, for example, between the first superconducting layer 16 and the second superconducting layer 26. There is, for example, an air gap between the first superconducting layer 16 and the second superconducting layer 26. The first superconducting layer 16 and the second superconducting layer 26 may be in contact with each other.

The connection layer 30 is an oxide superconducting layer. The connection layer 30 includes a rare earth element (RE), barium (Ba), copper (Cu), and oxygen (O). The connection layer 30 includes, for example, a rare earth element (RE), barium (Ba), copper (Cu), and oxygen (O). The connection layer 30 includes, for example, at least one rare earth element (RE) selected from the group consisting of yttrium (Y), lanthanum (La), neodymium (Nd), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu).

The connection layer 30 of the fourth embodiment has the same configuration as the connection layer 30 of the first embodiment shown in FIGS. 1, 2, and 3.

FIG. 15 is a schematic plan view of the connection layer of the fourth embodiment. FIG. 15 shows an arrangement pattern of high-density regions 30a and low-density regions 30b of the connection layer 30 in a plane parallel to the interface between the first superconducting layer 16 and the connection layer 30.

The plurality of high-density regions 30a include a first high-density region 30a1, a second high-density region 30a2, and a third high-density region 30a3. The first high-density region 30a1 is an example of a first region. Furthermore, the second high-density region 30a2 is an example of a second region. Furthermore, the third high-density region 30a3 is an example of a fourth region.

At least one low density region 30b includes a first low density region 30b1 and a second low density region 30b2. The first low density region 30b1 is an example of a third region. Further, the second low density region 30b2 is an example of a fifth region.

For example, the first high density region 30a1, the second high density region 30a2, and the first low density region 30b1 are provided between the first superconducting layer 16 and the third superconducting layer 46.

The length of the connection layer 30 in the first direction is shorter than the length of the connection layer 30 in the second direction. In other words, the connection layer 30 extends in the second direction. In other words, the first direction is the short side direction of the connection layer 30, and the second direction is the long side direction of the connection layer 30.

The first direction and the second direction are parallel to the interface between the first superconducting layer 16 and the connection layer 30. The second direction is perpendicular to the first direction.

In the third embodiment of the superconducting wire 400, for example, a current flows from the first superconducting wire 401 through the connection layer 30, the connection member 403, and the connection layer 30 to the second superconducting wire 402.

In the superconducting wire 400 of the third embodiment, the second superconducting wire 402 is located in the second direction with respect to the first superconducting wire 401. The second superconducting layer 26 is located in a second direction with respect to the first superconducting layer 16. In the superconducting wire 400 of the third embodiment, current flows in the connection layer 30 in the second direction.

The first superconducting wire 401 and the connection member 403 are connected using the connection layer 30, so that the connection structure connecting the first superconducting wire 401 and the connection member 403 has low electrical resistance and high mechanical strength. Also, the second superconducting wire 402 and the connection member 403 are connected using the connection layer 30, so that the connection structure connecting the second superconducting wire 402 and the connection member 403 has low electrical resistance and high mechanical strength.

Therefore, the connection structure connecting the first superconducting wire 401 and the second superconducting wire 402 has low electrical resistance and high mechanical strength. Therefore, the superconducting wire 400 has low electrical resistance and high mechanical strength.

It is also possible to connect three or more superconducting wires to form an even longer superconducting wire.

(First modification)
FIG. 16 is a schematic cross-sectional view of a first modification of the superconducting wire of the fourth embodiment. The superconducting wire 410 of the first modification of the fourth embodiment differs from the superconducting wire 400 of the fourth embodiment in that it includes a reinforcing material 60.

The reinforcing material 60 is provided between the first superconducting wire 401 and the second superconducting wire 402. The reinforcing material 60 is provided, for example, between the first superconducting layer 16 and the second superconducting layer 26.

For example, the reinforcing material 60 is in contact with the first superconducting wire 401 and the second superconducting wire 402. The reinforcing material 60 is in contact with the connection layer 30, for example.

By providing the reinforcing material 60, the mechanical strength of the superconducting wire 410 is improved.

The reinforcing material 60 is, for example, a metal or a resin. The reinforcing material 60 is, for example, a solder. The reinforcing material 60 is, for example, a solder containing silver (Ag) and indium (In).

(Second modification)
FIG. 17 is a schematic cross-sectional view of a second modification of the superconducting wire of the fourth embodiment. The superconducting wire 420 of the second modification of the fourth embodiment differs from the superconducting wire 400 of the fourth embodiment in that the connection layer 30 includes a first region 30x and a second region 30y spaced apart from each other. different.

The connection layer 30 includes a first region 30x and a second region 30y. The first region 30x and the second region 30y are spaced apart.

The first region 30x is provided between the first superconducting layer 16 and the third superconducting layer 46. The first region 30x contacts the first superconducting layer 16. The first region 30x contacts the third superconducting layer 46.

The second region 30y is provided between the second superconducting layer 26 and the third superconducting layer 46. The second region 30y is in contact with the second superconducting layer 26. The second region 30y is in contact with the third superconducting layer 46.

(Third modification)
FIG. 18 is a schematic cross-sectional view of a third modification of the superconducting wire of the fourth embodiment. In the superconducting wire 430 of the third modification of the fourth embodiment, a part of the surface of the first superconducting layer 16 facing the third superconducting layer 46 is exposed, and a part of the surface of the second superconducting layer 26 facing the third superconducting layer 43 This differs from the superconducting wire 420 of the second modification of the fourth embodiment in that a part of the surface facing the superconducting layer 46 is exposed.

There is an area where the connection layer 30 is not present near the end of the upper surface of the first superconducting layer 16 on the side of the second superconducting layer 26. Also, there is an area where the connection layer 30 is not present near the end of the upper surface of the second superconducting layer 26 on the side of the first superconducting layer 16.

(Fourth modification)
FIG. 19 is a schematic cross-sectional view of a fourth modification of the superconducting wire of the fourth embodiment. The superconducting wire 440 of the fourth modification of the fourth embodiment differs from the superconducting wire 430 of the third modification of the fourth embodiment in that it includes a reinforcing material 60.

The reinforcing material 60 is provided between the first superconducting wire 401 and the second superconducting wire 402. The reinforcing material 60 is provided, for example, between the first superconducting layer 16 and the second superconducting layer 26. The reinforcing material 60 is provided, for example, between the first superconducting layer 16 and the third superconducting layer 46. The reinforcing material 60 is provided, for example, between the second superconducting layer 26 and the third superconducting layer 46. The reinforcing material 60 is provided, for example, between the first region 30x and the second region 30y.

The inclusion of the reinforcing material 60 improves the mechanical strength of the superconducting wire 440.

The reinforcing material 60 is, for example, metal or resin. The reinforcing material 60 is, for example, solder. The reinforcing material 60 is, for example, a solder containing silver (Ag) and indium (In).

It is also possible to apply the superconducting layer connection structure of the second embodiment or the superconducting layer connection structure of the third embodiment to the fourth embodiment and its modified examples.

As described above, according to the fourth embodiment and the modified example, a superconducting wire having low electrical resistance and high mechanical strength can be realized by connecting two superconducting wires to a long length.

Fifth Embodiment
The superconducting coil of the fifth embodiment includes the superconducting wire of the fourth embodiment. Hereinafter, some of the contents that overlap with the fourth embodiment may be omitted.

Figure 20 is a schematic perspective view of a superconducting coil of the fifth embodiment. Figure 21 is a schematic cross-sectional view of a superconducting coil of the fifth embodiment.

The superconducting coil 700 of the fifth embodiment is used as a coil for generating a magnetic field in superconducting equipment such as NMR, MRI, heavy particle beam therapy equipment, or superconducting magnetic levitation railway vehicles.

The superconducting coil 700 includes a winding frame 110, a first insulating plate 111a, a second insulating plate 111b, and a winding portion 112. The winding portion 112 includes a superconducting wire 120 and an interwire layer 130.

FIG. 20 shows a state in which the first insulating plate 111a and the second insulating plate 111b are removed.

The winding frame 110 is made of, for example, fiber-reinforced plastic. The superconducting wire 120 has, for example, a tape shape. As shown in FIG. 20, the superconducting wire 120 is wound around the winding frame 110 in a concentric so-called pancake shape around the winding central axis C.

In FIG. 20, the first direction is the coil radial direction. The second direction is the circumferential direction of the coil. The first direction is the direction in which the central winding axis C extends.

The interwire layer 130 has a function of fixing the superconducting wire 120. The interwire layer 130 has a function of suppressing the superconducting wire 120 from being destroyed by vibrations during use of the superconducting device or by mutual friction.

The first insulating plate 111a and the second insulating plate 111b are made of, for example, fiber reinforced plastic. The first insulating plate 111a and the second insulating plate 111b have a function of insulating the winding portion 112 from the outside. The winding portion 112 is located between the first insulating plate 111a and the second insulating plate 111b.

The superconducting wire of the fourth embodiment is used as the superconducting wire 120.

As described above, according to the fifth embodiment, a superconducting coil with improved characteristics can be realized by using superconducting wire with low electrical resistance and high mechanical strength.

Sixth Embodiment
The superconducting device of the sixth embodiment is a superconducting device including the superconducting coil of the fifth embodiment. Hereinafter, some of the description overlapping with the fifth embodiment will be omitted.

FIG. 22 is a block diagram of a superconducting device according to the sixth embodiment. The superconducting device of the sixth embodiment is a heavy ion beam therapy device 800. Heavy particle beam therapy device 800 is an example of a superconducting device.

The heavy particle beam therapy device 800 includes an injection system 50, a synchrotron accelerator 52, a beam transport system 54, an irradiation system 56, and a control system 58.

The injection system 50 has a function of, for example, generating carbon ions used for treatment and pre-accelerating the carbon ions for injection into the synchrotron accelerator 52. The injection system 50 includes, for example, an ion source and a linear accelerator.

The synchrotron accelerator 52 has a function of accelerating the carbon ion beam incident from the injection system 50 to an energy suitable for treatment. The superconducting coil 700 of the third embodiment is used in the synchrotron accelerator 52.

The beam transport system 54 has the function of transporting the carbon ion beam injected from the synchrotron accelerator 52 to the irradiation system 56. The beam transport system 54 has, for example, a bending electromagnet.

The irradiation system 56 has a function of irradiating a patient as an irradiation target with the carbon ion beam incident from the beam transport system 54. The irradiation system 56 has, for example, a rotating gantry that can irradiate the carbon ion beam from any direction. The superconducting coil 700 of the third embodiment is used in the rotating gantry.

The control system 58 controls the injection system 50, the synchrotron accelerator 52, the beam transport system 54, and the irradiation system 56. The control system 58 is, for example, a computer.

In the heavy particle beam therapy device 800 of the sixth embodiment, the superconducting coil 700 of the third embodiment is used for the synchrotron accelerator 52 and the rotating gantry. Therefore, a heavy ion beam therapy device 800 with excellent characteristics is realized.

In the sixth embodiment, the heavy particle beam therapy device 800 has been described as an example of a superconducting device, but the superconducting device may be a nuclear magnetic resonance apparatus (NMR), a magnetic resonance imaging apparatus (MRI), or a superconducting It may be a magnetic levitation railway vehicle.

(Example 1)
An oxide superconducting wire with a length of 10.5 cm, in which an intermediate layer and a GdBa ₂ Cu ₃ O _7-δ layer (oxide superconducting layer) are formed on a Hastelloy base material and covered with a protective layer of silver and copper, is I have prepared a book. A portion 1.0 cm from one end was wet-etched using a mixed solution of nitric acid, ammonia, and hydrogen peroxide to expose the oxide superconducting layer.

Powders of Gd ₂ O ₃ , BaCO ₃ and CuO were prepared, weighed appropriately, and then thoroughly mixed, and the mixed powder was compression molded to produce a green compact. The obtained green compact was sintered at 930° C. to produce an oxide superconductor having a composition of GdBa ₂ Cu ₃ O _7-δ . By crushing the obtained oxide superconductor by hitting it in a mortar and sorting out particles with a suitable diameter using a sieve etc., particles with a median major axis of 5 μm or more and a median minor axis of 2 μm or less are obtained. We fabricated superconductor powder with a high aspect ratio.

The obtained superconductor powder was mixed with an organometallic salt solution in which Gd(OCOCH ₃ ) ₂ , Ba(OCOCH ₃ ) ₂ , and Cu(OCOCH ₃ ) ₂ were dissolved, in a weight ratio of 1:2, to prepare a slurry.

The obtained slurry is applied to the exposed oxide superconducting layer of one of the above superconducting wires, and then heated to 500°C in an oxygen atmosphere to perform a first heat treatment to connect the superconducting wires. A film of layers was formed.

The obtained connection layer was placed at a distance of 0.25 cm and 0.5 cm from the above connection layer and the end of the wire. The film of the connection layer was wiped with the tip of a soft cotton swab in a width of 0.04 cm parallel to the edge, centered at a position of 0.75 cm, and the film was removed to form a stripe.

The part of the superconducting wire on which the connection layer forming the stripes was placed was placed on top of the part of the other superconducting wire with the exposed superconducting layer facing each other.

The overlapping wires were clamped from above and below with a jig and pressure was applied.

A second heat treatment was performed by heating the sample to 780° C. in an air atmosphere while being held in a jig. Thereafter, it was cooled to around room temperature, oxygen gas was introduced into the furnace, and it was heated to 500° C. in an oxygen atmosphere to perform a third heat treatment to form a superconducting wire connection structure.

After connecting the superconducting wire, terminals were attached to both ends and the temperature dependence of electrical resistance was measured. A clear superconducting transition was confirmed at around 93 K with a transition width of approximately 1 K. The critical current value after the superconducting transition for this connection structure is set as a reference value of 1.0, and the relative critical current values are shown in the following examples and comparative examples.

(Comparative Example 1)
Two oxide superconducting wires with a length of 10.5 cm were prepared, _each wire having an intermediate layer and a _{GdBa2Cu3O7 -δ} layer (oxide superconducting layer) formed on a Hastelloy substrate and covered with a protective layer of silver and copper. A portion 1.0 cm from one end was wet etched using a mixed solution of nitric acid, ammonia, and hydrogen peroxide to expose the oxide superconducting layer.

Powders of Gd ₂ O ₃ , BaCO ₃ and CuO were prepared, weighed appropriately, and then thoroughly mixed, and the mixed powder was compression molded to produce a green compact. The obtained green compact was sintered at 930° C. to produce an oxide superconductor having a composition of GdBa ₂ Cu ₃ O _7-δ . The obtained oxide superconductor is pulverized by hitting it in a mortar, and particles with an appropriate diameter are sorted using a sieve, etc., to obtain particles with a median length of 5 μm or more and a median length of 2 μm or less. We fabricated superconductor powder with a high aspect ratio.

The obtained superconductor powder and an organic metal salt solution in which Gd(OCOCH ₃ ) ₂ , Ba(OCOCH ₃ ) ₂ , and Cu(OCOCH ₃ ) ₂ were dissolved were mixed at a weight ratio of 1:2 to prepare a slurry. .

After applying the slurry to the exposed oxide superconducting layer of one of the above superconducting wires, the part of the superconducting wire to which the slurry was applied is faced to the part of the other superconducting wire with the exposed superconducting layer. superimposed.

The stacked wire rods were sandwiched from above and below with a jig and pressurized.

While still clamped in the jig, the wire was heated to 780°C in an air atmosphere to carry out the first heat treatment. It was then cooled to near room temperature, oxygen gas was introduced into the furnace, and the wire was heated to 500°C in an oxygen atmosphere to carry out the second heat treatment, forming a connection structure for the superconducting wire.

After connecting the superconducting wire, terminals were attached to both ends and the temperature dependence of electrical resistance was measured. A clear superconducting transition was confirmed at 93 K with a transition width of approximately 1 K. The critical current value after the superconducting transition was 0.9.

(Example 2)
An oxide superconducting wire with a length of 10.5 cm, in which an intermediate layer and a GdBa ₂ Cu ₃ O _7-δ layer (oxide superconducting layer) are formed on a Hastelloy base material and covered with a protective layer of silver and copper, is I have prepared a book. A portion 1.0 cm from one end was wet-etched using a mixed solution of nitric acid, ammonia, and hydrogen peroxide to expose the oxide superconducting layer.

Powders of Gd ₂ O ₃ , BaCO ₃ and CuO were prepared, appropriately weighed, thoroughly mixed, and the mixed powder was compressed to produce a green compact. The obtained green compact was sintered at 930°C to produce an oxide superconductor with a GdBa ₂ Cu ₃ O _7-δ composition. The obtained oxide superconductor was pulverized by beating in a mortar, and particles of an appropriate diameter were selected using a sieve or the like to produce a superconductor powder with a high aspect ratio, with a median major axis of 5 μm or more and a median minor axis of 2 μm or less.

The obtained superconductor powder and an organic metal salt solution in which Gd(OCOCH ₃ ) ₂ , Ba(OCOCH ₃ ) ₂ , and Cu(OCOCH ₃ ) ₂ were dissolved were mixed at a weight ratio of 1:2 to prepare a slurry. .

The obtained slurry is applied to the exposed oxide superconducting layer of one of the above superconducting wires, and then heated to 500°C in an oxygen atmosphere to perform a first heat treatment to connect the superconducting wires. A film of layers was formed.

The resulting connection layer was wiped with the tip of a soft cotton swab in a 0.04 cm width parallel to the end, centered at positions 0.25 cm, 0.5 cm, and 0.75 cm from the end of the connection layer and wire, to remove the film and form a stripe.

The part of the superconducting wire on which the connection layer forming the stripes was placed was placed on top of the part of the other superconducting wire with the exposed superconducting layer facing each other.

The overlapping wires were clamped from above and below with a jig and pressure was applied.

While still clamped in the jig, the wire was heated to 780°C in an air atmosphere to carry out a second heat treatment. It was then cooled to near room temperature, oxygen gas was introduced into the furnace, and the wire was heated to 500°C in an oxygen atmosphere to carry out a third heat treatment, forming a connection structure for the superconducting wire.

The overlapping wires were soaked in a low-viscosity epoxy resin that hardens at room temperature, and left to stand at room temperature overnight, allowing the resin to penetrate and harden in the gaps between the stripes.

When we attached terminals to both ends of the superconducting wire after connection and measured the temperature dependence of the electrical resistance, we confirmed a clear superconducting transition at around 93 K and a transition width of about 1 K, and the critical current value after the superconducting transition was 1.0. It became.

Example 3
A wire and a slurry were prepared in the same manner as in Example 1. After the first heat treatment, the connection layer formed on the superconducting layer was wiped off in a width of 0.05 cm parallel to the second direction, centered at positions 0.125 cm and 0.275 cm from the end of the long side, to create a stripe.

The part of the superconducting wire on which the connection layer forming the stripes is mounted and the part of the other superconducting wire on which the superconducting layer is exposed are placed facing each other and subjected to a second heat treatment in an atmospheric atmosphere and a third heat treatment in an oxygen atmosphere. Heat treatment was performed to form a connection structure.

After connecting the superconducting wire, terminals were attached to both ends and the temperature dependence of electrical resistance was measured. A clear superconducting transition was confirmed at around 93 K with a transition width of approximately 1 K, and the critical current value after the superconducting transition was 1.0.

Example 4
A wire and a slurry were prepared in the same manner as in Example 1, and after the first heat treatment, the connection layer formed on the superconducting layer was wiped off in a width of 0.04 cm parallel to the second direction, centered at a position 0.2 cm from the end of the long piece, and the connection layer was also wiped off in a width of 0.04 cm parallel to the end, centered at positions 0.25 cm, 0.5 cm, and 0.75 cm from the end of the wire, to prepare a lattice-shaped low-density region.

The part of the superconducting wire with the connection layer on it and the part of the other superconducting wire with the exposed superconducting layer were placed facing each other and pressurized, and a second heat treatment was performed in an air atmosphere and a third heat treatment in an oxygen atmosphere to form a connection structure.

When we attached terminals to both ends of the superconducting wire after connection and measured the temperature dependence of the electrical resistance, we confirmed a clear superconducting transition at around 93 K and a transition width of about 1 K, and the critical current value after the superconducting transition was 1.0. It became.

Example 5
A wire and a slurry were prepared in the same manner as in Example 1, and after the first heat treatment, the connection layer formed on the superconducting layer was wiped off multiple times, alternately from both sides, over a width of 0.04 cm from the side of the wire to the center, to create a low-density region.

The part of the superconducting wire with the connection layer on it and the part of the other superconducting wire with the exposed superconducting layer were placed facing each other and pressurized, and a second heat treatment was performed in an air atmosphere and a third heat treatment in an oxygen atmosphere to form a connection structure.

After connecting the superconducting wire, terminals were attached to both ends and the temperature dependence of electrical resistance was measured. A clear superconducting transition was confirmed at around 93 K with a transition width of approximately 1 K, and the critical current value after the superconducting transition was 1.0.

(Example 6)
A wire rod and slurry were prepared in the same manner as in Example 1, and after the first heat treatment, the connection layer formed on the superconducting layer was cut into 0.04 cm width from one corner to the opposite diagonal corner at each corner. The connection layer was wiped off to create diagonal low-density regions.

The part of the superconducting wire on which the connection layer is placed and the part of the other superconducting wire with the exposed superconducting layer facing each other, pressurized, and subjected to a second heat treatment in an atmospheric atmosphere and a third heat treatment in an oxygen atmosphere, A connection structure was formed.

After connecting the superconducting wire, terminals were attached to both ends and the temperature dependence of electrical resistance was measured. A clear superconducting transition was confirmed at around 93 K with a transition width of approximately 1 K, and the critical current value after the superconducting transition was 1.0.

(Example 7)
An oxide superconducting wire with a length of 10.5 cm, in which an intermediate layer and a GdBa ₂ Cu ₃ O _7-δ layer (oxide superconducting layer) are formed on a Hastelloy base material and covered with a protective layer of silver and copper, is I have prepared a book. A portion 1.0 cm from one end was wet-etched using a mixed solution of nitric acid, ammonia, and hydrogen peroxide to expose the oxide superconducting layer.

Powders of Gd ₂ O ₃ , BaCO ₃ and CuO were prepared, appropriately weighed, thoroughly mixed, and the mixed powder was compressed to produce a green compact. The obtained green compact was sintered at 930°C to produce an oxide superconductor with a GdBa ₂ Cu ₃ O _7-δ composition. The obtained oxide superconductor was pulverized by beating in a mortar, and particles of an appropriate diameter were selected using a sieve or the like to produce a superconductor powder with a high aspect ratio, with a median major axis of 5 μm or more and a median minor axis of 2 μm or less.

The obtained superconductor powder was mixed with an organometallic salt solution in which Gd(OCOCH ₃ ) ₂ , Ba(OCOCH ₃ ) ₂ , and Cu(OCOCH ₃ ) ₂ were dissolved, in a weight ratio of 1:2, to prepare a slurry A.

Further, the superconductor powder and an organic metal salt solution in which Gd(OCOCH ₃ ) ₂ , Ba(OCOCH ₃ ) ₂ , and Cu(OCOCH ₃ ) ₂ were dissolved were mixed at a weight ratio of 5:1 to prepare slurry B. .

The obtained slurry B was applied using a dispenser to a width of 0.04 cm parallel to the end, centered at positions 0.25 cm, 0.5 cm, and 0.75 cm from the end of the exposed oxide superconducting layer of one of the superconducting wires described above, and then the remaining portion was coated with slurry A using a dispenser.

A first heat treatment was performed by heating to 500° C. in an oxygen atmosphere to form a connection layer film of the superconducting wire.

The part of the superconducting wire on which the connection layer forming the stripes was placed was placed on top of the part of the other superconducting wire with the exposed superconducting layer facing each other.

The overlapping wires were clamped from above and below with a jig and pressure was applied.

A second heat treatment was performed by heating the sample to 780° C. in an air atmosphere while being sandwiched between the jigs. Thereafter, it was cooled to around room temperature, oxygen gas was introduced into the furnace, and it was heated to 500° C. in an oxygen atmosphere to perform a third heat treatment to form a superconducting wire connection structure.

After connecting, terminals were attached to both ends of the superconducting wire and the temperature dependence of the electrical resistance was measured, and a clear superconducting transition was confirmed at around 93K with a transition width of about 1K. The critical current value of this connection structure after superconducting transition was 1.0.

(Example 8)
An oxide superconducting wire with a length of 10.5 cm, in which an intermediate layer and a GdBa ₂ Cu ₃ O _7-δ layer (oxide superconducting layer) are formed on a Hastelloy base material and covered with a protective layer of silver and copper, is I have prepared a book. A portion 1.0 cm from one end was wet-etched using a mixed solution of nitric acid, ammonia, and hydrogen peroxide to expose the oxide superconducting layer.

Powders of Gd ₂ O ₃ , BaCO ₃ and CuO were prepared, appropriately weighed, thoroughly mixed, and the mixed powder was compressed to produce a green compact. The obtained green compact was sintered at 930°C to produce an oxide superconductor with a GdBa ₂ Cu ₃ O _7-δ composition. The obtained oxide superconductor was pulverized by beating in a mortar, and particles of an appropriate diameter were selected using a sieve or the like to produce a superconductor powder with a high aspect ratio, with a median major axis of 5 μm or more and a median minor axis of 2 μm or less.

The particles smaller than the above obtained during the sorting were further pulverized for 3 hours or more using a ball mill to produce a superconductor powder with a median particle size of 3 μm or more and a low aspect ratio.

The two types of superconductor powders thus obtained were mixed with an organometallic salt solution in which Gd(OCOCH ₃ ) ₂ , Ba(OCOCH ₃ ) ₂ , and Cu(OCOCH ₃ ) ₂ were dissolved, in a weight ratio of 1:1:4, to prepare slurry A.

Further, only the high aspect ratio superconductor powder and an organic metal salt solution containing Gd(OCOCH ₃ ) ₂ , Ba(OCOCH ₃ ) ₂ , and Cu(OCOCH ₃ ) ₂ are mixed at a weight ratio of 5:1, Slurry B was produced.

The obtained slurry B was applied to one of the superconducting wires at a distance of 0.25 cm and 0.5 cm from the end of the exposed oxide superconducting layer wire. After applying the slurry to a width of 0.04 cm parallel to the edge using a dispenser, centering on a position of 0.75 cm, slurry A was applied using a dispenser to the remaining part.

A first heat treatment was performed by heating to 500° C. in an oxygen atmosphere to form a connection layer film of the superconducting wire.

The part with the connecting layer that formed the stripes of superconducting wire was placed face-to-face with the part of the other superconducting wire where the superconducting layer was exposed, and then they were layered together.

The overlapping wires were clamped from above and below with a jig and pressure was applied.

While still clamped in the jig, the wire was heated to 780°C in an air atmosphere to carry out a second heat treatment. It was then cooled to near room temperature, oxygen gas was introduced into the furnace, and the wire was heated to 500°C in an oxygen atmosphere to carry out a third heat treatment, forming a connection structure for the superconducting wire.

After connecting, terminals were attached to both ends of the superconducting wire and the temperature dependence of the electrical resistance was measured, and a clear superconducting transition was confirmed at around 93K with a transition width of about 1K. The critical current value of this connection structure after superconducting transition was 1.1.

Example 9
Three oxide superconducting wires were prepared, each of which had an intermediate layer and a GdBa ₂ Cu ₃ O _7-δ layer (oxide superconducting layer) formed on a Hastelloy substrate and was covered with a protective layer of silver and copper. One of the wires was 2.0 cm long, and the remaining two were 10 cm long. The 2.0 cm wire was wet etched between both ends, and the two 10 cm wires were wet etched 1.0 cm from one end using a mixed solution of nitric acid, ammonia, and hydrogen peroxide to expose the oxide superconducting layer.

Powders of Gd ₂ O ₃ , BaCO ₃ and CuO were prepared, weighed appropriately, and then thoroughly mixed, and the mixed powder was compression molded to produce a green compact. The obtained green compact was sintered at 930° C. to produce an oxide superconductor having a composition of GdBa2Cu3O7-δ. By crushing the obtained oxide superconductor by hitting it in a mortar and sorting out particles with a suitable diameter using a sieve etc., particles with a median major axis of 5 μm or more and a median minor axis of 2 μm or less are obtained. We fabricated superconductor powder with a high aspect ratio.

The obtained superconductor powder was mixed with an organometallic salt solution in which Gd(OCOCH ₃ ) ₂ , Ba(OCOCH ₃ ) ₂ , and Cu(OCOCH ₃ ) ₂ were dissolved, in a weight ratio of 1:2, to prepare a slurry.

The obtained slurry was applied to the entire exposed oxide superconducting layer of the 2.0 cm superconducting wire described above, and then heated to 500°C in an oxygen atmosphere to perform a first heat treatment, thereby forming a film for the connection layer of the superconducting wire.

The resulting connection layer was wiped with the tip of a soft cotton swab at positions 0.25 cm, 0.5 cm, and 0.75 cm from both ends of the connection layer and wire, respectively, and at the center of the wire in the second direction, parallel to the ends and with a width of 0.04 cm, to remove the film and form stripes.

To obtain the structure shown in Figure 14, the portion of the 2.0 cm superconducting wire on which the film of the connection layer was formed was placed face-to-face with the portions of the two 10 cm superconducting wires on which the superconducting layers were exposed.

The stacked wire rods were sandwiched from above and below with a jig and pressurized.

A second heat treatment was performed by heating the sample to 780° C. in an air atmosphere while being held in a jig. Thereafter, it was cooled to around room temperature, oxygen gas was introduced into the furnace, and it was heated to 500° C. in an oxygen atmosphere to perform a third heat treatment to form a superconducting wire connection structure.

After connecting, terminals were attached to both ends of the superconducting wire and the temperature dependence of the electrical resistance was measured, and a clear superconducting transition was confirmed at around 93K with a transition width of about 1K. The relative critical current value of this connection structure after superconducting transition was 1.0.

(Example 10)
After forming a connection structure according to the procedure of Example 9, solder containing silver and indium is placed on the surface where the 10 cm superconducting wires of the connection structure face each other, and the solder is melted and bonded by heating at 200°C to form a reinforcing material. And so.

After connecting the superconducting wire, terminals were attached to both ends and the temperature dependence of electrical resistance was measured. A clear superconducting transition was confirmed near 93 K with a transition width of approximately 1 K. In addition, the relative critical current value after the superconducting transition was 1.0.

(Example 11)
A superconducting wire and a slurry were prepared according to the procedure of Example 9, and after applying the slurry to a 2.2 cm superconducting wire and performing the first heat treatment, the obtained connection layer was applied to both the connection layer and the wire. At positions 0.25 cm, 0.5 cm, and 0.75 cm from the edge, respectively, and in a width of 0.04 cm parallel to the edge, wipe the connecting layer membrane with the tip of a soft cotton swab to remove the membrane and form stripes. did. Furthermore, a film having a width of 0.2 cm at the center of the wire was removed.

The portion of the 2.0 cm superconducting wire to which the slurry had been applied was placed face-to-face with the portion of the 10 cm superconducting wire with the superconducting layer exposed, and after the slurry was applied to the exposed oxide superconducting layer, the portion of the superconducting wire to which the slurry had been applied was placed face-to-face with the portion of the other superconducting wire with the superconducting layer exposed.

The wire was clamped from above and below with a jig, and the same heat treatment as in Example 9 was carried out while applying pressure to form a connection structure for the superconducting wire, and measurements were then carried out.

A clear superconducting transition was confirmed at around 93 K, with a transition width of approximately 1 K. In addition, the critical current value after the superconducting transition was 1.0.

Example 12
The superconducting wire and slurry were prepared according to the procedure of Example 9, the slurry was applied to a 2.2 cm superconducting wire and the first heat treatment was performed, and the resulting connection layer was wiped with the tip of a soft cotton swab at positions 0.25 cm and 0.5 cm from both ends of the connection layer and wire, respectively, in a width of 0.04 cm parallel to the ends, and the film was removed to form a stripe. Furthermore, the film in the center of the wire with a width of 0.5 cm was removed.

The part of the 2.0 cm superconducting wire coated with the slurry and the part of the 10 cm superconducting wire with the exposed superconducting layer are stacked facing each other, and the slurry of the superconducting wire is coated after the slurry is applied to the exposed oxide superconducting layer. The coated part and the exposed part of the superconducting layer of the other superconducting wire were stacked facing each other.

The superconducting wires were sandwiched from above and below with jigs, and while being pressurized, the same heat treatment as in Example 9 was performed to form a superconducting wire connection structure and measurements were performed.

A clear superconducting transition was confirmed at around 93K with a transition width of about 1K. Further, the relative critical current value after superconducting transition was 1.0.

(Example 13)
After forming a connection structure according to the procedure of Example 12, solder containing silver and indium was placed on the surfaces of the 10 cm superconducting wires of the connection structure facing each other, and the solder was melted and bonded by heating at 200°C to form a reinforcing material.

After connecting the superconducting wire, terminals were attached to both ends and the temperature dependence of electrical resistance was measured. A clear superconducting transition was confirmed near 93 K with a transition width of approximately 1 K. In addition, the relative critical current value after the superconducting transition was 1.0.

Although several embodiments of the invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and changes can be made without departing from the gist of the invention. For example, components of one embodiment may be replaced or modified with components of other embodiments. These embodiments and their modifications are included within the scope and gist of the invention, as well as within the scope of the invention described in the claims and its equivalents.

(Technical proposal 1)
a first superconducting layer;
a second superconducting layer;
A connection layer provided between the first superconducting layer and the second superconducting layer and containing crystal particles containing rare earth elements (RE), barium (Ba), copper (Cu), and oxygen (O). and,
Equipped with
The connection layer includes a first region, a second region, and a third region provided between the first region and the second region,
The first region and the second region contain the crystal grains, and the third region contains or does not contain the crystal grains,
the third region is exposed on a side surface of the connection layer;
In a cross section that is perpendicular to the interface between the first superconducting layer and the connection layer and includes the first region, the second region, and the third region, the first region of the crystal grains in the first region 1 and a second occupancy ratio of the crystal grains in the second region are larger than a third occupancy ratio of the crystal grains in the third region.

(Technical proposal 2)
The superconducting layer connection structure according to technical proposal 1, wherein the long axis distribution of the crystal grains has at least two peaks.

(Technical proposal 3)
A connection structure of a superconducting layer described in Technical Proposal 1 or Technical Proposal 2, wherein, in the cross section, a third width of the third region in a direction parallel to the interface is smaller than a first width of the first region in a direction parallel to the interface and a second width of the second region in a direction parallel to the interface.

(Technical proposal 4)
The superconducting layer connection structure according to technical proposal 3, wherein the third width is 50% or less of the first width and the second width.

(Technical proposal 5)
a length of the connection layer in a first direction along the interface is shorter than a length of the connection layer in a second direction along the interface perpendicular to the first direction;
A connection structure of superconducting layers described in any one of Technical Solutions 1 to 4, wherein the third region is exposed to a side surface of the connection layer in the first direction.

(Technical proposal 6)
A connection structure of a superconducting layer described in any one of Technical Proposals 1 to 5, wherein the third region contains the crystal grains, and the average value of the long diameter of the crystal grains contained in the third region is larger than the average value of the long diameter of the crystal grains contained in the first region.

(Technical proposal 7)
The superconducting layer according to any one of technical proposals 1 to 6, wherein the third region includes the crystal particles, and the crystal particles included in the third region include plate-shaped or flat-shaped crystal particles. connection structure.

(Technical proposal 8)
A connection structure of a superconducting layer described in any one of Technical Proposals 1 to 7, wherein the third region contains the crystal grains, and the third occupancy ratio is 10% or more and 50% or less of the first occupancy ratio.

(Technical proposal 9)
The superconducting layer connection structure according to any one of Technical Proposals 1 to 8, wherein the distribution of the long diameters of the crystal grains included in the first region has three peaks.

(Technical proposal 10)
A connection structure of a superconducting layer according to Technical Proposal 8, wherein the third region contains the crystal grains, and the distribution of the long diameters of the crystal grains contained in the third region has two peaks.

(Technical proposal 11)
The superconducting layer connection structure according to any one of technical proposals 1 to 10, wherein the third region includes a resin or a void.

(Technical proposal 12)
The connection layer further includes a fourth region and a fifth region between the second region and the fourth region,
The fourth region includes the crystal particles, and the fifth region includes or does not include the crystal particles,
In the cross section perpendicular to the interface, the second occupancy ratio and the fourth occupancy ratio of the crystal grains in the fourth region are higher than the fifth occupancy ratio of the crystal grains in the fifth region. big,
The superconducting layer connection structure according to any one of technical proposals 1 to 11, wherein the fifth region is exposed on a side surface of the connection layer.

(Technical proposal 13)
a first superconducting wire including a first superconducting layer;
a second superconducting wire including a second superconducting layer;
a third superconducting layer; and
a connection layer provided between the first superconducting layer and the third superconducting layer and between the second superconducting layer and the third superconducting layer, the connection layer including crystal grains containing a rare earth element (RE), barium (Ba), copper (Cu), and oxygen (O), the distribution of the major axis of the crystal grains having at least two peaks;
Equipped with
the connection layer between the first superconducting layer and the third superconducting layer includes a first region, a second region, and a third region provided between the first region and the second region;
the first region and the second region contain the crystal grains, and the third region may or may not contain the crystal grains;
the third region is exposed to a side surface of the connection layer,
A superconducting wire, wherein in a cross section perpendicular to the interface between the first superconducting layer and the connecting layer and including the first region, the second region, and the third region, a first occupation ratio of the crystal grains in the first region and a second occupation ratio of the crystal grains in the second region are greater than a third occupation ratio of the crystal grains in the third region.

(Technical proposal 14)
A superconducting wire according to Technical Proposal 13, wherein the distribution of the long diameters of the crystal grains has at least two peaks.

(Technical proposal 15)
A superconducting wire according to Technical Proposal 13 or Technical Proposal 14, wherein in the cross section, a third width of the third region in a direction parallel to the interface is smaller than a first width of the first region in a direction parallel to the interface and a second width of the second region in a direction parallel to the interface.

(Technical proposal 16)
The superconducting wire according to Technical Proposal 15, wherein the third width is 50% or less of the first width and the second width.

(Technical proposal 17)
The length of the connection layer in a first direction along the interface is shorter than the length in a second direction perpendicular to the first direction along the interface,
the third region is exposed on a side surface of the connection layer in the first direction;
The superconducting wire according to any one of Technical Plans 13 to 16, wherein the second superconducting layer is located in the second direction with respect to the first superconducting layer.

(Technical proposal 18)
A superconducting wire described in any one of Technical Proposals 13 to 17, wherein the third region contains the crystal grains, and the average value of the long diameter of the crystal grains contained in the third region is greater than the average value of the long diameter of the crystal grains contained in the first region.

(Technical proposal 19)
The superconducting wire according to any one of Technical Proposals 13 to 18, wherein the third region includes the crystal particles, and the crystal particles included in the third region include plate-shaped or flat-shaped crystal particles. .

(Technical proposal 20)
A superconducting wire described in any one of Technical Proposals 13 to 18, wherein the third region contains the crystal grains, and the third occupancy ratio is 10% or more and 50% or less of the first occupancy ratio.

(Technical proposal 21)
A superconducting coil comprising the superconducting wire according to any one of technical proposals 13 to 20.

(Technical proposal 22)
A superconducting device comprising the superconducting coil described in Technical Proposal 21.

16 First superconducting layer 26 Second superconducting layer 30 Connection layer 30a1 First high density region (first region)
30a2 second high density region (second region)
30a3 Third high density region (fourth region)
30b1 First low-density region (third region)
30b2 Second low-density region (fifth region)
30s Side surface 31 First crystal grain (crystal grain)
32 Second crystal particle (crystal particle)
34 Third crystal particle (crystal particle)
36 Resin 37 Void 46 Third superconducting layer 100 Connection structure 400 Superconducting wire 401 First superconducting wire 402 Second superconducting wire 700 Superconducting coil 800 Heavy particle beam therapy device (superconducting device)
w1: first width w2: second width w3: third width

Claims (22)

a first superconducting layer;
a second superconducting layer;
A connection layer provided between the first superconducting layer and the second superconducting layer and containing crystal particles containing rare earth elements (RE), barium (Ba), copper (Cu), and oxygen (O). and,
Equipped with
The connection layer includes a first region, a second region, and a third region provided between the first region and the second region,
The first region and the second region contain the crystal grains, and the third region contains or does not contain the crystal grains,
the third region is exposed on a side surface of the connection layer;
In a cross section that is perpendicular to the interface between the first superconducting layer and the connection layer and includes the first region, the second region, and the third region, the first region of the crystal grains in the first region 1 and a second occupancy ratio of the crystal grains in the second region are larger than a third occupancy ratio of the crystal grains in the third region. The superconducting layer connection structure according to claim 1, in which the distribution of the long diameters of the crystal grains has at least two peaks. The superconducting layer connection structure according to claim 1, wherein in the cross section, the third width of the third region in a direction parallel to the interface is smaller than the first width of the first region in a direction parallel to the interface and the second width of the second region in a direction parallel to the interface. 4. The superconducting layer connection structure according to claim 3, wherein the third width is 50% or less of the first width and the second width. a length of the connection layer in a first direction along the interface is shorter than a length of the connection layer in a second direction along the interface perpendicular to the first direction;
The superconducting layer connection structure according to claim 1 , wherein the third region is exposed to a side surface of the connection layer in the first direction. The superconducting layer connection structure according to claim 1, wherein the third region includes the crystal grains, and the average major axis of the crystal grains included in the third region is greater than the average major axis of the crystal grains included in the first region. 2. The superconducting layer connection structure according to claim 1, wherein the third region includes the crystal particles, and the crystal particles included in the third region include plate-shaped or flat-shaped crystal particles. The superconducting layer connection structure according to claim 1, wherein the third region includes the crystal grains, and the third occupancy ratio is 10% or more and 50% or less of the first occupancy ratio. The superconducting layer connection structure according to claim 1, wherein the distribution of the long diameters of the crystal grains contained in the first region has three peaks. 10. The superconducting layer connection structure according to claim 9, wherein the third region includes the crystal grains, and a distribution of major diameters of the crystal grains included in the third region has two peaks. The superconducting layer connection structure according to claim 1, wherein the third region includes a resin or a void. The connection layer further includes a fourth region and a fifth region between the second region and the fourth region,
The fourth region includes the crystal particles, and the fifth region includes or does not include the crystal particles,
In the cross section perpendicular to the interface, the second occupancy ratio and the fourth occupancy ratio of the crystal grains in the fourth region are higher than the fifth occupancy ratio of the crystal grains in the fifth region. big,
The superconducting layer connection structure according to claim 1, wherein the fifth region is exposed on a side surface of the connection layer. A first superconducting wire including a first superconducting layer;
a second superconducting wire including a second superconducting layer;
a third superconducting layer;
Provided between the first superconducting layer and the third superconducting layer and between the second superconducting layer and the third superconducting layer, rare earth elements (RE), barium (Ba), A connection layer containing crystal grains containing copper (Cu) and oxygen (O), wherein the distribution of the long diameter of the crystal grains has at least two peaks;
Equipped with
The connection layer between the first superconducting layer and the third superconducting layer is provided between a first region, a second region, and the first region and the second region. a third region,
The first region and the second region contain the crystal grains, and the third region contains or does not contain the crystal grains,
the third region is exposed on a side surface of the connection layer;
In a cross section that is perpendicular to the interface between the first superconducting layer and the connection layer and includes the first region, the second region, and the third region, the first region of the crystal grains in the first region 1 and a second occupancy ratio of the crystal grains in the second region are larger than a third occupancy ratio of the crystal grains in the third region. The superconducting wire according to claim 13, wherein the distribution of the long diameters of the crystal grains has at least two peaks. The superconducting wire according to claim 13, wherein in the cross section, the third width of the third region in a direction parallel to the interface is smaller than the first width of the first region in a direction parallel to the interface and the second width of the second region in a direction parallel to the interface. The superconducting wire according to claim 15, wherein the third width is 50% or less of the first width and the second width. The length of the connection layer in a first direction along the interface is shorter than the length in a second direction perpendicular to the first direction along the interface,
the third region is exposed on a side surface of the connection layer in the first direction;
The superconducting wire according to claim 13, wherein the second superconducting layer is located in the second direction with respect to the first superconducting layer. The third region includes the crystal grains, and the average length of the crystal grains included in the third region is larger than the average length of the crystal grains included in the first region. The superconducting wire according to claim 13. The superconducting wire according to claim 13, wherein the third region includes the crystal particles, and the crystal particles included in the third region include plate-shaped or flat-shaped crystal particles. The superconducting wire according to claim 13, wherein the third region includes the crystal grains, and the third occupancy ratio is 10% or more and 50% or less of the first occupancy ratio. A superconducting coil comprising the superconducting wire according to any one of claims 13 to 20. A superconducting device comprising the superconducting coil according to claim 21.

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