Connection structure for superconducting layer, superconducting wire, superconducting coil, superconducting device, and connection method for superconducting layer

A connection structure for a superconducting layer comprising:

• a first superconducting layer;
• a second superconducting layer;
• and
• a connection layer disposed between the first superconducting layer and the second superconducting layer, the connection layer including crystal grains containing a rare earth element (RE), barium (Ba) copper (Cu), and oxygen (O) and at least one grain selected from the group consisting of a first grain containing a rare earth element (RE) and oxygen (O), a second grain containing barium (Ba), carbon (C), and oxygen (O), a third grain containing copper (Cu) and oxygen (O), and a fourth grain containing barium (Ba), copper (Cu) , and oxygen (O),
• wherein the crystal grains include a crystal grain having a plate shape or a flat shape.

A superconducting wire comprising:

• a first superconducting wire including a first superconducting layer;
• a second superconducting wire including a second superconducting layer;
• a third superconducting layer including a first surface and a second surface opposed to the first surface;
• and
• a connection layer disposed between the first superconducting layer and the third superconducting layer and between the second superconducting layer and the third superconducting layer and including crystal grains containing a rare earth element (RE), barium (Ba), copper (Cu), and oxygen (O), the crystal grains having a grain size distribution including a bimodal distribution,
• wherein the first superconducting layer and the second superconducting layer face the first surface of the third superconducting layer,
• wherein the bimodal distribution includes a first distribution including a first peak and a second distribution including a second peak,
• wherein a first grain size corresponding to the first peak is larger than a second grain size corresponding to the second peak, and
• wherein, among the crystal grans, crystal grains having a grain size corresponding to the first distribution include a crystal grain having a plate shape or a flat shape.

A superconducting wire comprising:

• a first superconducting wire including a first superconducting layer;
• a second superconducting wire including a second superconducting layer;
• a third superconducting layer including a first surface and a second surface opposed to the first surface;
• and
• a connection layer disposed 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), and the connection layer including at least one grain selected from the group consisting of a first grain containing a rare earth element (RE) and oxygen (O), a second grain containing barium (Ba), carbon (C), and oxygen (O), a third grain containing copper (Cu) and oxygen (O), and a fourth grain containing barium. (Ba), copper (Cu), and oxygen (O),
• wherein the first superconducting layer and the second superconducting layer face the first surface of the third superconducting layer, and
• wherein the crystal grains includes a crystal grain having a plate shape or a flat shape.

A connection method for a superconducting layer comprising:

• preparing a first superconducting layer and a second superconducting layer;
• preparing slurry including a crystal grain containing a rare earth element (RE), barium (Ba), copper (Cu), and oxygen (O), a first grain containing a rare earth element (RE) and oxygen (O), a second grain containing barium (Ba), carbon (C), and oxygen (O), and a third grain containing copper (Cu) and oxygen (O);
• applying the slurry onto the second superconducting layer;
• superposing the first superconducting layer and the second superconducting layer with the slurry interposed between the first superconducting layer and the second superconducting layer;
• performing a first heat treatment at a first temperature;
• and
• performing a second heat treatment at a second temperature in an atmosphere having oxygen partial pressure equal to or higher than oxygen partial pressure in the first heat treatment.