JP2023122796A - Connection structure of superconducting layer, superconducting wire material, superconducting coil, superconducting device, and connection method of superconducting layer - Google Patents

Abstract

To provide a connection structure of a superconducting layer which can achieve low electric resistance and high mechanical strength.SOLUTION: A connection structure of a superconducting layer includes a first superconducting layer, a second superconducting layer, and a connection layer which is provided between the first superconducting layer and the second superconducting layer, contains crystal particles containing a rare earth element (RE), barium (Ba), copper (Cu) and oxygen (O), and a region having carbon atom concentration higher than carbon atom concentration of the crystal particles, and has distribution of a major axis of the crystal particles including bimodal distribution. The bimodal distribution has first distribution including a first peak, and second distribution including a second peak, and a first major axis corresponding to the first peak is larger than a second major axis corresponding to the second peak.SELECTED DRAWING: Figure 2

Description

TECHNICAL FIELD Embodiments of the present invention relate to a connection structure of superconducting layers, a superconducting wire, a superconducting coil, a superconducting device, and a method of connecting superconducting layers.

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

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. A connection structure for connecting superconducting wires is required to have low electrical resistance and high mechanical strength.

Japanese Patent No. 5828299 Japanese Patent No. 6675590 Japanese Patent No. 6178779

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

A superconducting layer connection structure of an embodiment is provided between a first superconducting layer, a second superconducting layer, and the first superconducting layer and the second superconducting layer, and comprises a rare earth element (RE), A crystal grain containing barium (Ba), copper (Cu), and oxygen (O), and a region having a carbon atom concentration higher than the carbon atom concentration of the crystal grain, wherein the distribution of the major diameters of the crystal grain is a connecting layer comprising a bimodal distribution, the bimodal distribution having a first distribution comprising a first peak and a second distribution comprising a second peak; A corresponding first major axis is greater than a second major axis corresponding to the second peak.

FIG. 2 is a schematic cross-sectional view of the superconducting layer connection structure of the first embodiment. FIG. 2 is an enlarged schematic cross-sectional view of part of the connection layer of the first embodiment; The figure which shows the definition of the long axis and short axis of the crystal grain of 1st Embodiment. FIG. 4 is a diagram showing the distribution of major diameters of crystal grains contained in the connection layer of the first embodiment; FIG. 2 is a process flow diagram of an example of a method for connecting superconducting layers according to the first embodiment. FIG. 4 is an enlarged schematic cross-sectional view of part of a connection layer in a modification of the first embodiment; The schematic cross section of the superconducting wire material of 2nd Embodiment. The schematic cross section of the 1st modification of the superconducting wire of 2nd Embodiment. The schematic cross section of the 2nd modification of the superconducting wire of 2nd Embodiment. The schematic cross section of the 3rd modification of the superconducting wire of 2nd Embodiment. The schematic cross section of the 4th modification of the superconducting wire of 2nd Embodiment. The schematic perspective view of the superconducting coil of 3rd Embodiment. FIG. 5 is a schematic cross-sectional view of a superconducting coil according to a third embodiment; The block diagram of the superconducting equipment of 4th Embodiment.

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

In this specification, the major diameter of a particle is the maximum length among the lengths between arbitrary two points on the circumference of the particle. The minor axis of a particle is the length of a line segment that passes through the midpoint of a line segment corresponding to the major axis, is perpendicular to the line segment, and has both ends at the outer periphery of the particle. The long and short diameters of the particles can be determined, for example, by image analysis of cross-sectional images using a scanning electron microscope (SEM). In this specification, a line segment corresponding to the major axis is referred to as a major axis. A line segment corresponding to the minor axis is called a minor axis.

Detection of elements contained in particles and the measurement of atomic concentrations of the elements can be performed using, for example, energy dispersive X-ray spectroscopy (EDX) or wavelength dispersive X-ray analysis (WDX). In addition, identification of substances contained in particles and the like can be performed using, for example, powder X-ray diffraction.

(First embodiment)
The superconducting layer connection structure of the first embodiment is provided between a first superconducting layer, a second superconducting layer, and the first superconducting layer and the second superconducting layer, and comprises a rare earth element (RE) , crystal grains containing barium (Ba), copper (Cu), and oxygen (O), and a region having a carbon atom concentration higher than that of the crystal grains, and the distribution of the major diameters of the crystal grains is bilateral. a connecting layer comprising a modal distribution. The bimodal distribution has a first distribution including a first peak and a second distribution including a second peak, the first major axis corresponding to the first peak corresponding to the second peak larger than the second major axis.

FIG. 1 is a schematic cross-sectional view of a connection structure of superconducting layers according to 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 elongate the superconducting wires.

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

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

The first substrate 12 is, for example, 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, 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), 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, for example, a chemical composition represented by (RE)Ba ₂ Cu ₃ O _δ (RE is a rare earth element, 6≦δ≦7). The first superconducting layer 16 is, 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≦ 7) has a chemical composition represented by

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

The first superconducting layer 16 is formed, for example, on the first intermediate layer 14 by 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).

A first intermediate layer 14 is provided between the first substrate 12 and the first superconducting layer 16 . The first intermediate layer 14 contacts, for example, the first superconducting layer 16 . 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 contains, for example, a rare earth oxide. The first intermediate layer 14 has, for example, a laminated 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 laminated from the first substrate 12 side.

The second substrate 22 is, for example, 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), 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 represented by (RE)Ba ₂ Cu ₃ O _δ (RE is a rare earth element, 6≦δ≦7). The second superconducting layer 26 is, 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≦ 7) has a chemical composition represented by

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

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

A second intermediate layer 24 is provided between the second substrate 22 and the second superconducting layer 26 . The second intermediate layer 24 contacts, for example, the second superconducting layer 26 . 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 contains, for example, 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.

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

The connection layer 30 is an oxide superconducting layer. The connection layer 30 contains a rare earth element (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), holmium (Ho ), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu).

FIG. 2 is an enlarged schematic cross-sectional view of part of the connection layer of the first embodiment.

The connection layer 30 includes first crystal grains 31 , second crystal grains 32 , carbon-containing particles 33 and pores 34 . The connection layer 30 is formed by sintering the first crystal grains 31 , the second crystal grains 32 and the carbon-containing particles 33 .

The first crystal grains 31 and the second crystal grains 32 are examples of crystal grains. The carbon-containing particles 33 are an example of regions having a carbon atom concentration higher than that of the crystal grains.

The connection layer 30 is, for example, porous. For example, voids 34 (Void) exist between particles included in the connection layer 30 . The connection layer 30 may not have the holes 34 .

The first crystal grains 31 contain a rare earth element (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 represented by (RE)Ba ₂ Cu ₃ O _δ (RE is a rare earth element, 6≦δ≦7). The first crystal grains 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≦ 7) has a chemical composition represented by

The first crystal grains 31 are superconductors.

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

The median value of the aspect ratios of the first crystal grains 31 is, for example, 2 or more.

FIG. 3 is a diagram showing the definition of the major axis and minor axis of the crystal grains of the first embodiment. FIG. 3 is a diagram showing the first crystal grain 31 as an example.

The major diameter of a particle is the maximum length among the lengths between arbitrary two points on the circumference of the particle. The minor axis of a particle is the length of a line segment that passes through the midpoint of a line segment corresponding to the major 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. 3 is the length of the line segment L1. In addition, the minor axis in the case of the first crystal grain 31 shown in FIG. 3 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. 3 is L1/S1.

The median length of the first crystal grains 31 is, for example, 100 nm or more and 10 μm or less. The median length of the first crystal grain 31 is, for example, greater than the thickness (t in FIG. 2) of the connection layer 30 in the direction from the first superconducting layer 16 to the second superconducting layer 26 .

The major axis direction of the first crystal grains 31 is, for example, inclined with respect to the interface between the first superconducting layer 16 and the connection layer 30 . The angle of the major 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 the first tilt angle. The first tilt 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 represented by (RE)Ba ₂ Cu ₃ O _δ (RE is a rare earth element, 6≦δ≦7).

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 represented by (RE)Ba ₂ Cu ₃ O _δ (RE is a rare earth element, 6≦δ≦7).

The second crystal grains 32 are, for example, superconductors.

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

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

The second crystal grains 32 are, for example, spherical or irregular. The median aspect ratio of the second crystal grains 32 is, for example, smaller than the median aspect ratio of the first crystal grains 31 . The median aspect ratio of the second crystal grains 32 is less than 2, for example.

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 second crystal grains 32 is, for example, smaller than the thickness of the connection layer 30 in the direction from the first superconducting layer 16 to the second superconducting layer 26 (t in FIG. 2).

The median length of the first crystal grains 31 is, for example, 10 to 1000 times the median length of the second crystal grains 32 .

FIG. 4 is a diagram showing the major diameter distribution of crystal grains contained in the connection layer of the first embodiment. FIG. 4 shows the major diameter distribution of the first crystal grains 31 and the second crystal grains 32 contained in the connection layer 30 .

As shown in FIG. 4, the long diameter distribution of the crystal grains contained in the connection layer 30 includes a bimodal distribution. A bimodal distribution has a first distribution containing a first peak (Pk1 in FIG. 4) and a second distribution containing a second peak (Pk2 in FIG. 4).

Note that the long diameter distribution of the crystal grains contained in the connection layer 30 may be a multimodal distribution with three or more peaks.

Crystal grains included in the first distribution are the first crystal grains 31 . Crystal grains included in the second distribution are the second crystal grains 32 .

The major axis corresponding to the first peak Pk1 is the first major axis (d1 in FIG. 4). The major axis corresponding to the second peak Pk2 is the second major axis (d2 in FIG. 4).

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 as large as the second major axis d2.

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

The first major axis d1 is, for example, larger than the thickness of the connection layer 30 in the direction from the first superconducting layer 16 to the second superconducting layer 26 (t in FIG. 2). The second major axis d2 is, for example, smaller than the thickness of the connection layer 30 in the direction from the first superconducting layer 16 to the second superconducting layer 26 (t in FIG. 2).

The carbon-containing particles 33 contain carbon (C). The atomic concentration of the carbon-containing particles 33 is higher than the atomic concentration of the first crystal grains 31 . The atomic concentration of the carbon-containing particles 33 is higher than the atomic concentration of the second crystal grains 32 .

The atomic concentration of the carbon-containing particles 33 is, for example, ten times or more the atomic concentration of the first crystal grains 31 . The atomic concentration of the carbon-containing particles 33 is, for example, ten times or more the atomic concentration of the second crystal grains 32 .

The carbon-containing particles 33 contain barium (Ba), carbon (C), and oxygen (O), for example. The carbon-containing particles 33 are barium carbonate, for example. The carbon-containing particles 33 have, for example, a chemical composition denoted by Ba ₂ CO ₃ .

The carbon-containing particles 33 are, for example, spherical or irregular. The aspect ratio of the carbon-containing particles 33 is smaller than that of the first crystal grains 31, for example. The aspect ratio of the carbon-containing particles 33 is less than 2, for example.

The median length of the carbon-containing particles 33 is, for example, smaller than the median length of the first crystal grains 31 . The median length of the carbon-containing particles 33 is, for example, smaller than the first length d1.

The median length of the carbon-containing particles 33 is, for example, smaller than the median length of the second crystal grains 32 . The median length of the carbon-containing particles 33 is, for example, smaller than the second length d2.

The median length of the carbon-containing particles 33 is, for example, 10 nm or more and less than 1 μm.

The number of carbon-containing particles 33 in the connection layer 30 is smaller than the number of the second crystal grains 32 in the connection layer 30, for example. The number of carbon-containing particles 33 in the connection layer 30 is, for example, 1/10 or less of the number of the second crystal grains 32 in the connection layer 30 .

In the superconducting layer connection method of the first embodiment, a first superconducting layer and a second superconducting layer are prepared, and a rare earth element (RE), barium (Ba), copper (Cu), and oxygen (O) are added. An oxide superconductor containing: and a powder of an organic acid salt of copper (Cu) are dissolved to prepare an organic metal salt solution, a slurry is prepared by mixing the first crystal particles in the organic metal salt solution, and the slurry is formed on the first superconducting layer. is applied, and heat treatment is performed with the slurry sandwiched between the first superconducting layer and the second superconducting layer.

An example of a method for connecting superconducting layers according to the first embodiment will be described below.

FIG. 5 is a process flow diagram of an example of a method for connecting superconducting layers according to the first embodiment. As shown in FIG. 5, an example of the superconducting layer connection method of the first embodiment includes a conductive layer preparation step S01, an oxide superconductor preparation step S02, a first crystal grain preparation step S03, and an organometallic solution preparation step. S04, a slurry preparation step S05, a slurry application step S06, and a heat treatment step S07.

First, the first superconducting layer 16 and the second superconducting layer 26 are prepared (S01). The first superconducting layer 16 and the second superconducting layer 26 are formed using, for example, the MOD method, the PLD method, or the MOCVD method.

Next, an oxide superconductor containing a rare earth element (RE), barium (Ba), copper (Cu), and oxygen (O) is formed (S02). An oxide superconductor is formed, for example, by a solid state reaction method. The oxide superconductor is produced, for example, by mixing and compressing powders of rare earth element (RE) oxide, barium (Ba) carbonate, and copper (Cu) oxide to form a compact. It is produced by sintering the green compact.

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

Next, the oxide superconductor is pulverized to produce first crystal grains 31 (S03). The first crystal grains 31 contain a rare earth element (RE), barium (Ba), copper (Cu), and oxygen (O). For example, particles having a desired size and shape are selected as the first crystal particles 31 from the particles produced by pulverization.

For example, the first crystal grains 31 are produced so that the first crystal grains 31 have a plate-like or flat shape. For example, the first crystal grains 31 are produced such that the median aspect ratio of the first crystal grains 31 is 2 or more.

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

An organic metal salt solution is prepared by dissolving an organic acid salt powder of a rare earth element (RE), a powder of an organic acid salt of barium (Ba), and a powder of an organic acid salt of copper (Cu) (S04). For example, Gd(OCOCH ₃ ) ₂ powder, Ba(OCOCH ₃ ) ₂ powder, and Cu(OCOCH ₃ ) ₂ powder are used to prepare an organometallic salt solution.

Next, the first crystal grains 31 are mixed with the prepared organic metal salt solution to prepare a slurry (S05).

Next, the prepared slurry is applied onto the first superconducting layer 16 (S06).

Next, heat treatment is performed with the slurry sandwiched between the first superconducting layer 16 and the second superconducting layer 26 (S07). The heat treatment is performed, for example, while pressing the first superconducting layer 16 and the second superconducting layer 26 in a direction from the first superconducting layer 16 toward the second superconducting layer 26 .

The heat treatment is performed, for example, in an atmosphere containing oxygen. The heat treatment is performed, for example, at a temperature of 800° C. or lower. A connection layer 30 is formed by heat treatment.

By firing the slurry, the second crystal grains 32 are formed. The second crystal grains 32 contain rare earth elements (RE), barium (Ba), copper (Cu), and oxygen (O).

The median length of the second crystal grains 32 is smaller than the median length of the first crystal grains 31 . The median aspect ratio of the second crystal grains 32 is, for example, smaller than the median aspect ratio of the first crystal grains 31 .

Carbon-containing particles 33 are formed by firing the slurry. The carbon-containing particles 33 contain barium (Ba), carbon (C), and oxygen (O), for example. The median length of the carbon-containing particles 33 is, for example, smaller than the median length of the first crystal grains 31 . In addition, the median length of the carbon-containing particles 33 is, for example, smaller than the median length of 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 connection structure 100 of the superconducting layers of the first embodiment is formed.

It should be noted that the oxide superconductor can also be formed using, for example, the MOD method, the PLD method, or the MOCVD method instead of the solid phase reaction method.

Next, the operation and effects of the superconducting layer connection structure and the superconducting layer connection method of the first embodiment will be described.

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

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 connecting structure. A connection structure for connecting superconducting wires is required to have low electrical resistance and high mechanical strength.

In the superconducting layer connection method of the first embodiment, the connection layer 30 connecting the first superconducting layer 16 and the second superconducting layer 26 includes first crystal grains 31 having a large major axis and second crystal grains 31 having a small major axis. of crystal grains 32 and carbon-containing particles 33 . By including the first crystal grains 31, the second crystal grains 32, and the carbon-containing particles 33 in the connection layer 30, the connection structure 100 of the superconducting layers with low electric resistance and high mechanical strength can be realized. Details will be described below.

The superconducting layer connection structure 100 of the first embodiment includes the first crystal grains 31 having a large major axis, so that the electrical resistance of the connection layer 30 is reduced. By providing the first crystal grains 31 having a large major axis, the crystal grain interfaces occupying the connection layer 30 are reduced. Therefore, an increase in the electrical resistance of the connection layer 30 due to the interfacial resistance of the crystal grain interface is suppressed.

In the connection structure 100 of the superconducting layers of the first embodiment, the second crystal grains 32 having a small long axis fill the space between the first crystal grains 31 having a large long axis. The first crystal grains 31 and the second crystal grains 32 are bonded by the second crystal grains 32 , and the mechanical strength of the connection layer 30 is improved.

As the carbon atom concentration in the crystal grains of the oxide superconductor increases, the conductivity of the crystal grains decreases. The carbon atom concentration of the first crystal grains 31 is lower than the carbon atom concentration of the carbon-containing particles 33 . Also, the carbon atom concentration of the second crystal grains 32 is lower than the carbon atom concentration of the carbon-containing particles 33 .

By lowering the carbon atom concentrations of the first crystal grains 31 and the second crystal grains 32, the electrical resistance of the connection layer 30 can be reduced. In particular, the electrical resistance of the connection layer 30 can be reduced by lowering the carbon atom concentration of the first crystal grains 31 that contribute highly to the reduction of the electrical resistance of the connection layer 30 .

As described above, according to the superconducting layer connection structure 100 of the first embodiment, low electrical resistance and high mechanical strength can be achieved.

From the viewpoint of reducing the electrical resistance of the connection layer 30 , the carbon atom concentration of the carbon-containing particles 33 is preferably 10 times or more the carbon atom concentration of the first crystal grains 31 . From the viewpoint of reducing the electrical resistance of the connection layer 30 , the carbon atom concentration of the carbon-containing particles 33 is preferably 10 times or more the carbon atom concentration of the second crystal grains 32 .

In other words, from the viewpoint of reducing the electrical resistance of the connection layer 30 , the carbon-containing particles 33 of the first crystal grains 31 preferably have a carbon atom concentration of 1/10 or less of the carbon-containing particles 33 . From the viewpoint of reducing the electrical resistance of the connection layer 30 , the carbon-containing particles 33 of the second crystal grains 32 preferably have a carbon atom concentration of 1/10 or less of the carbon-containing particles 33 .

From the viewpoint of reducing the electrical resistance of the connection layer 30 , the number of the carbon-containing particles 33 in the connection layer 30 is preferably less than the number of the second crystal grains 32 in the connection layer 30 . More preferably, the number of carbon-containing particles 33 in connection layer 30 is 1/10 or less of the number of second crystal grains 32 in connection layer 30 .

From the viewpoint of reducing the electrical resistance of the connection layer 30 , the median length of the carbon-containing particles 33 is preferably smaller than the median length of the first crystal grains 31 . From the viewpoint of reducing the electrical resistance of the connection layer 30 , the median length of the carbon-containing particles 33 is preferably smaller than the median length of the second crystal grains 32 .

The carbon-containing particles 33 do not have superconducting properties and have low electrical conductivity. Therefore, by reducing the number of carbon-containing particles 33, an increase in electrical resistance of the connection layer 30 can be suppressed. In addition, since the long diameter of the carbon-containing particles 33 is reduced, an increase in electrical resistance of the connection layer 30 can be suppressed.

From the viewpoint of reducing the electrical resistance of the connection layer 30, the median length of the first crystal grains 31 is preferably 100 nm or more, more preferably 1 μm or more, and even more preferably 3 μm or more. . From the viewpoint of reducing the electrical resistance of the connection layer 30, the first major axis d1 is preferably 100 nm or more, more preferably 1 μm or more, and even more preferably 3 μm or more.

From the viewpoint of reducing the electrical resistance of the connection layer 30, the median value of the major axis of the first crystal grains 31 is the thickness of the connection layer 30 in the direction from the first superconducting layer 16 to the second superconducting layer 26 (Fig. It is preferably greater than t) in 2. From the viewpoint of reducing the electrical resistance of the connection layer 30, the first major axis d1 is greater than the thickness of the connection layer 30 in the direction from the first superconducting layer 16 to the second superconducting layer 26 (t in FIG. 2). Large is preferred.

From the viewpoint of reducing the electrical resistance of the connection layer 30 , the median aspect ratio of the first crystal grains 31 is preferably larger than the median aspect ratio of the second crystal grains 32 . The median aspect ratio of the second crystal grains 32 is preferably smaller than the median aspect ratio of the first crystal grains 31 .

From the viewpoint of reducing the electrical resistance of the connection layer 30, the median aspect ratio of the first crystal grains 31 is preferably 2 or more, more preferably 4 or more, and further preferably 6 or more. preferable.

From the viewpoint of reducing the electrical resistance of the connection layer 30, the median aspect ratio of the second crystal grains 32 is preferably less than 2, more preferably less than 1.5.

From the viewpoint of reducing the electrical resistance of the connection layer 30, the median value of the first inclination angle of the major axis direction of the first crystal grains 31 with respect to the interface between the first superconducting layer 16 and the connection layer 30 is 15 degrees or more. , more preferably 20 degrees or more, and even more preferably 30 degrees or more.

From the viewpoint of increasing the mechanical strength of the connection layer 30, the median major axis of the second crystal grains 32 is preferably less than 1 μm, more preferably 500 nm or less, and further preferably less than 200 nm. preferable. From the viewpoint of increasing the mechanical strength of the connection layer 30, the second major axis d2 is preferably less than 1 μm, more preferably 500 nm or less, and even more preferably less than 200 nm.

From the viewpoint of increasing the mechanical strength of the connection layer 30 , the median value of the major axis of the first crystal grains 31 is preferably 10 times or more the major axis of the second crystal grains 32 . From the viewpoint of increasing the mechanical strength of the connection layer 30, the first major axis d1 is preferably ten times or more the second major axis d2.

From the viewpoint of increasing the mechanical strength of the connection layer 30, the chemical composition of the first crystal grains 31 and the chemical composition of the second crystal grains 32 are preferably the same.

In the superconducting layer connection method of the first embodiment, the first crystal grains 31 and the second crystal grains 32 are formed in independent manufacturing steps. The first crystal grains 31 are formed by pulverizing a prefabricated oxide superconductor. On the other hand, the second crystal grains 32 are formed by the MOD method. Therefore, the properties of the first crystal grains 31 and the properties of the second crystal grains 32 can be easily optimized to achieve low electrical resistance and high mechanical strength of the connection layer 30 .

From the viewpoint of reducing the electrical resistance of the connection layer 30, the properties particularly required for the first crystal grains 31 are, for example, high crystallinity, a large major diameter of the grains, a high aspect ratio, and a low carbon atom concentration. is. A prefabricated oxide superconductor can have high crystallinity and a low carbon atom concentration by selecting optimum manufacturing conditions. Further, when the oxide superconductor is pulverized to produce the first crystal particles 31, by selecting the optimum pulverization conditions and particle selection conditions, the first crystals having a large major diameter and a high aspect ratio can be obtained. Particles 31 can be produced.

From the viewpoint of improving the mechanical strength of the connection layer 30, the properties especially required for the second crystal grains 32 are that the long diameter of the grains is small and the sinterability between the grains is high. Also, from the viewpoint of not degrading the superconducting properties of the first superconducting layer 16 and the second superconducting layer 26, the second crystal grains 32 are required to be formed at a low temperature. By using the MOD method, it is possible to form the second crystal grains 32 having a small major axis and high sinterability between the grains at a low temperature.

Moreover, by using the MOD method, the number of carbon-containing particles 33 in the connection layer 30 and the length of the carbon-containing particles 33 can be reduced. Therefore, the electrical resistance of the connection layer 30 is reduced.

As described above, according to the superconducting layer connection method of the first embodiment, it is possible to manufacture a superconducting layer connection structure having low electrical resistance and high mechanical strength.

The prefabricated oxide superconductor is preferably formed using a solid phase reaction method. The preformed oxide superconductor is produced by mixing and compressing powders of rare earth element (RE) oxide, barium (Ba) carbonate, and copper (Cu) oxide. and sintering the green compact. By the above method, it is possible to produce an oxide superconductor with high crystallinity and low carbon atom concentration.

The heat treatment for forming the second crystal grains 32 is preferably performed in an oxygen-containing atmosphere from the viewpoint of achieving high sinterability.

The heat treatment for forming the second crystal grains 32 is preferably performed at a temperature of 800° C. or less, more preferably 700° C. or less. By performing the heat treatment at a low temperature, deterioration of the superconducting properties of the first superconducting layer 16 and the second superconducting layer 26 can be suppressed.

From the viewpoint of increasing the mechanical strength of the connection layer 30 , the median length of the second crystal grains 32 is preferably smaller than the median length of the first crystal grains 31 . From the viewpoint of increasing the mechanical strength of the connection layer 30 , the median aspect ratio of the second crystal grains 32 is preferably smaller than the median aspect ratio of the first crystal grains 31 .

(Modification)
FIG. 6 is an enlarged schematic cross-sectional view of a part of the connection layer of the modified example of the first embodiment. The connection layer 30 of the modification differs from the connection layer 30 of the first embodiment in that instead of the carbon-containing particles 33, carbon-containing portions 35 are included.

The first crystal grains 31 and the second crystal grains 32 are examples of crystal grains. The carbon-containing portion 35 is an example of a region having a carbon atom concentration higher than that of the crystal grains.

The carbon-containing portion 35 contains carbon (C). The atomic concentration of carbon-containing portion 35 is higher than the atomic concentration of first crystal grain 31 . The atomic concentration of the carbon-containing portion 35 is higher than the atomic concentration of the second crystal grains 32 .

The atomic concentration of the carbon-containing portion 35 is, for example, ten times or more the atomic concentration of the first crystal grain 31 . The atomic concentration of the carbon-containing portion 35 is, for example, ten times or more the atomic concentration of the second crystal grains 32 .

Carbon-containing portion 35 includes, for example, barium (Ba), carbon (C), and oxygen (O). Carbon-containing portion 35 is, for example, barium carbonate. Carbon-containing portion 35 has, for example, a chemical composition denoted by Ba ₂ CO ₃ .

The carbon-containing portion 35 has an irregular shape.

As described above, according to the connection structure of the superconducting layers of the first embodiment and the modified example, low electric resistance and high mechanical strength can be realized.

(Second embodiment)
In the superconducting wire of the second embodiment, the first superconducting wire including the first superconducting layer, the second superconducting wire including the second superconducting layer, and the first surface face the first surface. A third superconducting layer having a second surface, provided between the first superconducting layer and the third superconducting layer, and between the second superconducting layer and the third superconducting layer, and a rare earth element (RE), barium (Ba), copper (Cu), and oxygen (O), and a region having a carbon atom concentration higher than the carbon atom concentration of the crystal grain, a connecting layer whose distribution includes a bimodal distribution. The first superconducting layer and the second superconducting layer are located on the side of the first surface of the third superconducting layer. The bimodal distribution has a first distribution including a first peak and a second distribution including a second peak, the first major axis corresponding to the first peak corresponding to the second peak larger than the second major axis. The superconducting wire of the second embodiment uses the connection structure of the superconducting layers of the first embodiment as a structure for connecting the first superconducting wire and the second superconducting wire. In the following, a part of the description of the content that overlaps with that of the first embodiment will be omitted.

FIG. 7 is a schematic cross-sectional view of a superconducting wire according to the second embodiment. A superconducting wire 400 of the second embodiment includes a first superconducting wire 401 , a second superconducting wire 402 , and a connecting member 403 . A superconducting wire 400 of the second embodiment is elongated by connecting a first superconducting wire 401 and a second superconducting wire 402 using a connecting member 403 .

First superconducting wire 401 includes first substrate 12 , first intermediate layer 14 , first superconducting layer 16 and first protective layer 18 . A 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 connection member 403 have the same structures as 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 . The connection layer 30 contacts the first superconducting layer 16 . The connection layer 30 contacts the 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 connecting layer 30 between the first superconducting layer 16 and the third superconducting layer 46 and the connecting 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 . For example, an air gap exists between the first superconducting layer 16 and the second superconducting layer 26 .

The connection layer 30 is an oxide superconducting layer. The connection layer 30 contains a rare earth element (RE), barium (Ba), copper (Cu), and oxygen (O). The connection layer 30 contains, for example, a rare earth element (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), holmium (Ho ), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu).

The connection layer 30 of the second embodiment has the same configuration as the connection layer 30 of the first embodiment shown in FIG.

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

By connecting first superconducting wire 401 and connecting member 403 using connecting layer 30, the connecting structure connecting first superconducting wire 401 and connecting member 403 has low electrical resistance and high mechanical strength. Prepare. In addition, since second superconducting wire 402 and connecting member 403 are connected using connecting layer 30, the connecting structure connecting second superconducting wire 402 and connecting member 403 has low electric resistance and high mechanical resistance. strength.

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

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

(First modification)
FIG. 8 is a schematic cross-sectional view of a first modification of the superconducting wire of the second embodiment. A superconducting wire 410 of the first modification of the second embodiment differs from the superconducting wire 400 of the second embodiment in that a reinforcing member 60 is provided.

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

The reinforcing member 60 contacts, for example, the first superconducting wire 401 and the second superconducting wire 402 . The reinforcement member 60 contacts the connection layer 30, for example.

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

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

(Second modification)
FIG. 9 is a schematic cross-sectional view of a second modification of the superconducting wire of the second embodiment. A superconducting wire 420 of a second modification of the second embodiment differs from superconducting wire 400 of the second embodiment in that the connection layer 30 includes a first region 30a and a second region 30b separated from each other. different.

The connection layer 30 includes a first region 30a and a second region 30b. The first region 30a and the second region 30b are separated.

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

A second region 30 b is provided between the second superconducting layer 26 and the third superconducting layer 46 . The second region 30 b contacts the second superconducting layer 26 . The second region 30 b contacts the third superconducting layer 46 .

(Third modification)
FIG. 10 is a schematic cross-sectional view of a third modification of the superconducting wire of the second embodiment. In a superconducting wire 430 of a third modification of the second embodiment, a part of the surface of the first superconducting layer 16 facing the third superconducting layer 46 is exposed, and the third superconducting layer 46 of the second superconducting layer 26 is partially exposed. This differs from the superconducting wire 420 of the second modification of the second embodiment in that a part of the surface facing the superconducting layer 46 of the second embodiment is exposed.

On the upper surface of the first superconducting layer 16, there is a region where the connection layer 30 does not exist near the end on the second superconducting layer 26 side. In addition, there is a region where the connection layer 30 does not exist near the edge of the upper surface of the second superconducting layer 26 on the side of the first superconducting layer 16 .

(Fourth modification)
FIG. 11 is a schematic cross-sectional view of a fourth modification of the superconducting wire of the second embodiment. A superconducting wire 440 of the fourth modification of the second embodiment differs from the superconducting wire 430 of the third modification of the second embodiment in that a reinforcing member 60 is provided.

Reinforcing member 60 is provided between first superconducting wire 401 and second superconducting wire 402 . The reinforcement member 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 reinforcement member 60 is provided, for example, between the second superconducting layer 26 and the third superconducting layer 46 . The reinforcing member 60 is provided, for example, between the first region 30a and the second region 30b.

By providing reinforcing material 60, the mechanical strength of superconducting wire 440 is improved.

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

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

(Third embodiment)
A superconducting coil of the third embodiment includes the superconducting wire of the second embodiment. In the following, a part of the description may be omitted for the contents that overlap with the second embodiment.

FIG. 12 is a schematic perspective view of the superconducting coil of the third embodiment. FIG. 13 is a schematic cross-sectional view of the superconducting coil of the third embodiment.

The superconducting coil 700 of the third embodiment is used, for example, as a magnetic field generating coil for superconducting equipment such as NMR, MRI, heavy ion radiotherapy equipment, or superconducting magnetic levitation railway vehicles.

Superconducting coil 700 includes winding frame 110 , first insulating plate 111 a , second insulating plate 111 b , and winding portion 112 . Winding portion 112 has superconducting wire 120 and inter-wire layer 130 .

FIG. 13 shows a state in which the first insulating plate 111a and the second insulating plate 111b are removed.

The bobbin 110 is made of fiber-reinforced plastic, for example. Superconducting wire 120 is, for example, tape-shaped. As shown in FIG. 13, the superconducting wire 120 is wound around the winding frame 110 in a concentric so-called pancake shape around the winding center C. As shown in FIG.

Inter-wire layer 130 has a function of fixing superconducting wire 120 . The inter-wire layer 130 has a function of suppressing the destruction of the superconducting wires 120 due to vibration during use of the superconducting equipment and mutual friction.

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

The superconducting wire of the second embodiment is used for the superconducting wire 120 .

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

(Fourth embodiment)
A superconducting device of the fourth embodiment is a superconducting device including the superconducting coil of the third embodiment. In the following, a part of the description of the content overlapping with that of the third embodiment will be omitted.

FIG. 14 is a block diagram of the superconducting equipment of the fourth embodiment. A superconducting device of the fourth embodiment is a heavy ion radiotherapy device 800 . The heavy ion radiotherapy device 800 is an example of superconducting equipment.

The heavy ion radiotherapy 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 them to enter a synchrotron accelerator 52 . The injection system 50 has, for example, an ion source and a linear accelerator.

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

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

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

A 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.

The heavy ion radiotherapy device 800 of the fourth embodiment uses the superconducting coil 700 of the third embodiment for the synchrotron accelerator 52 and rotating gantry. Therefore, a heavy ion radiotherapy device 800 with excellent characteristics is realized.

In the fourth embodiment, as an example of superconducting equipment, the case of the heavy ion radiotherapy device 800 has been described. It may be a magnetic levitation railway vehicle.

(Example 1)
An intermediate layer and a GdBa ₂ Cu ₃ O _7-δ layer (oxide superconducting layer) were formed on a Hastelloy substrate, and covered with silver and copper protective layers. I prepared a book. A portion of 1.0 cm from one end was wet-etched using a mixed solution of nitric acid and ammonia and hydrogen peroxide to expose the oxide superconducting layer.

Powders of Gd ₂ O ₃ , BaCO ₃ and CuO were prepared, appropriately weighed, and thoroughly mixed, and the mixed powder was compression-molded to prepare a powder compact. By sintering the obtained compact at 930° C., an oxide superconductor having a composition of GdBa ₂ Cu ₃ O _7-δ was produced. The obtained oxide superconductor is pulverized in a mortar by beating it, and particles having a suitable diameter are screened with a sieve or the like to obtain an aspect having a median major axis of 5 μm or more and a median minor axis of 2 μm or less. A superconductor powder with a high ratio was produced.

The obtained two kinds of superconductor powders and an organometallic salt solution in which Gd(OCOCH ₃ ) ₂ , Ba(OCOCH ₃ ) ₂ and Cu(OCOCH ₃ ) ₂ are dissolved were mixed at a weight ratio of 1:2 to form a slurry. was made.

The resulting slurry was applied to the exposed oxide superconducting layer of one of the above superconducting wires. After that, the portion of the superconducting wire to which the slurry was applied and the portion of the other superconducting wire in which the superconducting layer was exposed were placed face to face.

The superimposed wire rod was sandwiched between jigs from above and below, and was pressurized.

A first heat treatment was performed by heating to 780° C. in an air atmosphere while being sandwiched between jigs. After that, it was cooled to around room temperature, oxygen gas was introduced into the furnace, and the furnace was heated to 500° C. in an oxygen atmosphere to perform a second heat treatment, thereby forming a connection structure of the superconducting wires.

Terminals were attached to both ends of the superconducting wire after connection, and the temperature dependence of the electrical resistance was measured. Assuming that the critical current value of this connection structure after the transition to superconductivity is 1.0 as a reference value, relative critical current values are shown in the following examples and comparative examples.

Observation of the cross section of the connecting portion with SEM and SEM-EDX revealed that the first crystal grains had a plate-like or flat shape and almost no carbon (C) was observed, and had a GdBa ₂ Cu ₃ O _7-δ composition, and an indeterminate crystal grain with a low aspect ratio. Second crystal grains of the GdBa ₂ Cu ₃ O _7-δ composition in the shape were confirmed. The average major axis of the first crystal grains is about 5 μm, and the average minor axis is 2 μm. there were. Further, irregular shaped carbon-containing particles 33 smaller than the second particles were confirmed around the second particles, and carbon (C) having an intensity of 10 times or more that of the first crystal particles was observed from these particles.

(Comparative example 1)
An intermediate layer and a GdBa ₂ Cu ₃ O _7-δ layer (oxide superconducting layer) were formed on a Hastelloy substrate, and covered with silver and copper protective layers. I prepared a book. A portion of 1.0 cm from one end was wet-etched using a mixed solution of nitric acid and ammonia and hydrogen peroxide to expose the oxide superconducting layer.

Powders of Gd ₂ O ₃ , BaCO ₃ and CuO were prepared, appropriately weighed, and thoroughly mixed, and the mixed powder was compression-molded to prepare a powder compact. By sintering the obtained compact at 930° C., an oxide superconductor having a composition of GdBa ₂ Cu ₃ O _7-δ was produced. The obtained oxide superconductor is pulverized in a mortar by beating it, and particles having a suitable diameter are screened with a sieve or the like to obtain an aspect having a median major axis of 5 μm or more and a median minor axis of 2 μm or less. A superconductor powder with a high ratio was produced.

The obtained superconductor powder, Gd ₂ O ₃ powder with a particle size of about 50 nm, BaCO ₃ powder with a particle size of about 70 nm, and CuO powder with a particle size of about 30 nm were mixed using a mortar. Water and sodium alginate were added to the obtained mixed powder to form a slurry.

After applying the slurry to the exposed oxide superconducting layer of one of the superconducting wires, the portion of the superconducting wire that has been coated with the slurry faces the portion of the other superconducting wire that has the superconducting layer exposed. superimposed on each other.

The superimposed wire rod was sandwiched between jigs from above and below, and was pressurized.

A first heat treatment was performed by heating to 780° C. in an air atmosphere while being sandwiched between jigs. After that, it was cooled to around room temperature, oxygen gas was introduced into the furnace, and the furnace was heated to 500° C. in an oxygen atmosphere to perform a second heat treatment, thereby forming a connection structure of the superconducting wires.

Terminals were attached to both ends of the superconducting wire after connection, and the temperature dependence of the electrical resistance was measured. Also, the critical current value after the transition to superconductivity was 0.8.

Observation of the cross section of the connecting portion by SEM and SEM-EDX revealed plate-like or flattened first crystal grains and amorphous second crystal grains with a low aspect ratio. Carbon (C) was detected on the surface of the second crystal grain. In addition, lumps of irregularly shaped carbon-containing particles 33 larger than those of Example 1 were observed, having a size of about 100 nm to 2 μm.

(Example 2)
Three oxide superconducting wires were prepared, each having an intermediate layer and a GdBa ₂ Cu ₃ O _7-δ layer (oxide superconducting layer) formed on a Hastelloy substrate and covered with silver and copper protective layers. The length of each was 2.2 cm for one and 10 cm for the remaining two. The 2.2 cm line is wet-etched between both ends, and the two 10 cm lines are wet-etched using a mixed solution of nitric acid, ammonia, and hydrogen peroxide at a distance of 1.0 cm from one end to form an oxide superconducting layer. exposed.

Powders of Gd ₂ O ₃ , BaCO ₃ and CuO were prepared, appropriately weighed, and thoroughly mixed, and the mixed powder was compression-molded to prepare a powder compact. By sintering the obtained compact at 930° C., an oxide superconductor having a composition of GdBa ₂ Cu ₃ O _7-δ was produced. The obtained oxide superconductor is pulverized in a mortar by beating it, and particles having a suitable diameter are screened with a sieve or the like to obtain an aspect having a median major axis of 5 μm or more and a median minor axis of 2 μm or less. A superconductor powder with a high ratio was produced.

Particles smaller than the above obtained during the selection were further pulverized using a ball mill for 3 hours or longer to produce a superconductor powder with a median particle size of 3 μm or more and a low aspect ratio of less than 2.

The obtained two kinds of superconductor powders and an organometallic salt solution in which Gd( _OCOCH3 ) ₂ , Ba( _OCOCH3 ) ₂ and Cu( _OCOCH3 ) ₂ were dissolved were mixed at a weight ratio of 1:1:4. , to prepare a slurry.

The resulting slurry was applied to the exposed oxide superconducting layer of the 2.2 cm superconducting wire. After that, the portion of the 2.2 cm superconducting wire to which the slurry was applied and the portion of the 10 cm superconducting wire where the superconducting layer was exposed were overlapped so as to form the structure shown in FIG.

The superimposed wire rod was sandwiched between jigs from above and below, and was pressurized.

A first heat treatment was performed by heating to 780° C. in an air atmosphere while being sandwiched between jigs. After that, it was cooled to around room temperature, oxygen gas was introduced into the furnace, and the furnace was heated to 500° C. in an oxygen atmosphere to perform a second heat treatment, thereby forming a connection structure of the superconducting wires.

Terminals were attached to both ends of the superconducting wire after connection, and the temperature dependence of the electrical resistance was measured. Also, the critical current value after the transition to superconductivity was 1.0.

(Modification 1)
After forming the connection structure according to the procedure of Example 2, solder containing silver and indium is placed on the surfaces of the connection structure where the 10 cm superconducting wires face each other, and the solder is heated at 200 ° C. to melt and bond the reinforcing material. and

Terminals were attached to both ends of the superconducting wire after connection, and the temperature dependence of the electrical resistance was measured. Also, the critical current value after the transition to superconductivity was 1.0.

(Modification 2)
A superconducting wire and a slurry are prepared according to the procedure of Example 2, the slurry is applied to the exposed portions of the superconducting layers of the two 10 cm superconducting wires, and the 2.2 cm superconducting wire and the two 10 cm superconducting wires. The parts coated with the slurry were placed face to face.

The superconducting wires were sandwiched between jigs from above and below, and heat treatment was performed in the same manner as in Example 2 while pressure was applied to form and measure the connection structure of the superconducting wires.

A clear superconducting transition was confirmed at around 93K and a transition width of about 1K. Also, the critical current value after the transition to superconductivity was 1.0.

(Modification 3)
A superconducting wire and a slurry were prepared according to the procedure of Example 2, and the superconducting wire with a length of 2.2 cm was coated in a range of 0.9 cm from each end of the exposed oxide superconducting layer, and then the structure shown in FIG. 10 was obtained. Thus, a portion of the 2.2 cm superconducting wire to which the slurry was applied and a portion of the 10 cm superconducting wire where the superconducting layer was exposed were placed face to face.

The superconducting wires were sandwiched between jigs from above and below, and heat treatment was performed in the same manner as in Example 2 while pressure was applied to form and measure the connection structure of the superconducting wires.

A clear superconducting transition was confirmed at around 93K and a transition width of about 1K. Also, the critical current value after the transition to superconductivity was 1.0.

(Modification 4)
After forming the connection structure according to the procedure of Modification 3, solder containing silver and indium is placed on the surfaces of the connection structure where the 10 cm superconducting wires face each other, and the solder is heated at 200 ° C. to melt and bond the reinforcing material. and

Terminals were attached to both ends of the superconducting wire after connection, and the temperature dependence of the electrical resistance was measured. Also, the critical current value after the transition to superconductivity was 1.0.

While several embodiments of the invention have been described, these embodiments have been 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, replacements, and modifications can be made without departing from the scope of the invention. For example, components of one embodiment may be substituted or modified with components of another embodiment. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the scope of the invention described in the claims and equivalents thereof.

16 First Superconducting Layer 26 Second Superconducting Layer 30 Connection Layer 31 First Crystal Grain 32 Second Crystal Grain 33 Carbon-containing Particle 35 Carbon-containing Portion 46 Third Superconducting Layer 100 Connection Structure 400 Second Embodiment superconducting wire 401 first superconducting wire 402 second superconducting wire 700 superconducting coil 800 heavy particle beam therapy device Pk1 first peak Pk2 second peak d1 first major diameter d2 second major diameter

Claims (20)

a first superconducting layer;
a second superconducting layer;
Crystal grains provided between the first superconducting layer and the second superconducting layer and containing a rare earth element (RE), barium (Ba), copper (Cu), and oxygen (O), and the crystal grains a region having a carbon atom concentration higher than the carbon atom concentration of the connection layer, wherein the distribution of the major diameters of the crystal grains includes a bimodal distribution;
with
The bimodal distribution has a first distribution including a first peak and a second distribution including a second peak,
The superconducting layer connection structure, wherein a first major axis corresponding to the first peak is larger than a second major axis corresponding to the second peak. 2. The connection structure of superconducting layers according to claim 1, wherein the carbon atom concentration of said region is ten times or more the carbon atom concentration of said crystal grains. 3. The connection structure of superconducting layers according to claim 1, wherein said region contains particles containing barium (Ba), carbon (C), and oxygen (O). 4. The connection structure of superconducting layers according to claim 3, wherein the median value of the major axis of said particles is smaller than said first major axis. 5. The connection structure of superconducting layers according to claim 3, wherein the median value of the major axis of said particles is smaller than said second major axis. The median aspect ratio of the crystal grains having the major axis corresponding to the first distribution is larger than the median aspect ratio of the crystal grains having the major axis corresponding to the second distribution. Item 6. The superconducting layer connection structure according to any one of items 5. The superconducting layer connection structure according to any one of claims 1 to 6, wherein the crystal grains having a major axis corresponding to the first distribution include plate-like or flat crystal grains. The first major axis is larger than the thickness of the connection layer in the direction from the first superconducting layer to the second superconducting layer,
The connection structure of superconducting layers according to any one of claims 1 to 7, wherein said second major axis is smaller than said thickness. a first superconducting wire including a first superconducting layer;
a second superconducting wire including a second superconducting layer;
a third superconducting layer having a first surface and a second surface facing the first surface;
Between the first superconducting layer and the third superconducting layer and between the second superconducting layer and the third superconducting layer, a rare earth element (RE), barium (Ba), Crystal grains containing copper (Cu) and oxygen (O), and a region having a carbon atom concentration higher than the carbon atom concentration of the crystal grains, and the distribution of major diameters of the crystal grains includes a bimodal distribution. a connection layer;
with
the first superconducting layer and the second superconducting layer are located on the first surface side of the third superconducting layer;
The bimodal distribution has a first distribution including a first peak and a second distribution including a second peak,
A superconducting wire, wherein a first major axis corresponding to the first peak is larger than a second major axis corresponding to the second peak. 10. The superconducting wire according to claim 9, wherein the carbon atom concentration of said region is 10 times or more the carbon atom concentration of said crystal grains. 11. The superconducting wire according to claim 9, wherein said region contains particles containing barium (Ba), carbon (C), and oxygen (O). 12. The superconducting wire according to claim 11, wherein the median major axis of said particles is smaller than said first major axis. 13. The superconducting wire according to claim 11, wherein the median length of the particles is smaller than the second length. A superconducting coil comprising the superconducting wire according to any one of claims 9 to 13. A superconducting device comprising the superconducting coil according to claim 14 . providing a first superconducting layer and a second superconducting layer;
Producing an oxide superconductor containing a rare earth element (RE), barium (Ba), copper (Cu), and oxygen (O),
pulverizing the oxide superconductor to produce first crystal particles,
preparing an organic metal salt solution by dissolving an organic acid salt powder of a rare earth element (RE), a powder of an organic acid salt of barium (Ba), and a powder of an organic acid salt of copper (Cu);
preparing a slurry by mixing the first crystal particles with the organometallic salt solution;
applying the slurry on the first superconducting layer;
A method of connecting superconducting layers, wherein a heat treatment is performed with the slurry sandwiched between the first superconducting layer and the second superconducting layer. The oxide superconductor is produced by mixing powder of rare earth element (RE) oxide, powder of barium (Ba) carbonate, and powder of copper (Cu) oxide and compressing them to produce a powder compact. 17. The method of connecting superconducting layers according to claim 16, wherein the superconducting layers are fabricated by sintering the green compact. 18. The method of connecting superconducting layers according to claim 16, wherein said heat treatment is performed at a temperature of 800[deg.] C. or less in an atmosphere containing oxygen. 19. The method for connecting superconducting layers according to claim 16, wherein the median aspect ratio of the first crystal grains is 2 or more. The heat treatment forms second crystal grains containing a rare earth element (RE), barium (Ba), copper (Cu), and oxygen (O),
The median length of the second crystal grains is smaller than the median length of the first crystal grains,
20. The method of connecting superconducting layers according to claim 16, wherein the median aspect ratio of the second crystal grains is smaller than the median aspect ratio of the first crystal grains. .

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