Magnesium diboride superconducting thin-film wire and method for producing same

Patent metadata

Field	Value
Publication number	US-10460862-B2
Application number	US-201515512014-A
Country	US
Kind code	B2
Filing date	Oct 16, 2015
Priority date	Nov 28, 2014
Publication date	Oct 29, 2019
Grant date	Oct 29, 2019

Abstract

An object of the invention is to provide: an MgB2 superconducting thin-film wire that exhibits excellent Jc characteristics even under a 20 K magnetic field; and a method for producing thereof. The MgB2 superconducting thin-film wire includes a long substrate and an MgB2 thin film formed on the long substrate. The MgB2 thin film has a microtexture such that MgB2 columnar crystal grains stand densely together on the surface of the long substrate, and has Tc of 30 K or higher. In grain boundary regions of the MgB2 columnar crystal grains, a predetermined transition metal element is dispersed and segregated. The predetermined transition metal element is an element having a body-centered cubic lattice structure.

First claim

The invention claimed is:

1. A magnesium diboride superconducting thin-film wire, comprising:
a long substrate;
a magnesium diboride thin film formed on the long substrate, wherein the magnesium diboride thin film includes magnesium diboride columnar crystal grains; and
a transition metal element layer formed on the magnesium diboride thin film, wherein the transition metal layer is diffused into grain boundaries of the magnesium diboride columnar crystal grains;
wherein:
the magnesium diboride thin film has a microtexture such that the magnesium diboride columnar crystal grains stand densely together on a surface of the long substrate, and
the transition metal element layer is formed from a predetermined transition metal element that has a body-centered cubic lattice structure.

2. The magnesium diboride superconducting thin-film wire according to claim 1 , wherein the magnesium diboride thin film has a laminate structure made up of a plurality of layers.

3. The magnesium diboride superconducting thin-film wire according to claim 2 , wherein the transition metal element layer is formed between the plurality of layers.

4. The magnesium diboride superconducting thin-film wire according to claim 2 , wherein the long substrate contains iron as a main constituent.

5. The magnesium diboride superconducting thin-film wire according to claim 1 , wherein the predetermined transition metal element contains at least iron or manganese.

6. The magnesium diboride superconducting thin-film wire according to claim 1 , wherein an additional layer of the transition metal element is formed between the long substrate and the magnesium diboride thin film.

7. The magnesium diboride superconducting thin-film wire according to claim 1 , wherein the predetermined transition metal element is vanadium.

8. The magnesium diboride superconducting thin-film wire according to claim 1 , wherein the predetermined transition metal element is manganese.

9. The magnesium diboride superconducting thin-film wire according to claim 1 , wherein the predetermined transition metal element is iron.

10. The magnesium diboride superconducting thin-film wire according to claim 1 , wherein the predetermined transition metal element is niobium.

11. The magnesium diboride superconducting thin-film wire according to claim 1 , wherein the predetermined transition metal element is molybdenum.

12. The magnesium diboride superconducting thin-film according to claim 1 , wherein the predetermined transition metal element is tantalum.

13. The magnesium diboride superconducting thin-film wire according to claim 1 , wherein the predetermined transition metal element is tungsten.

14. A method for producing a magnesium diboride superconducting thin-film wire comprising the steps of:
forming, on a long substrate, a magnesium diboride thin film having a microtexture such that magnesium diboride columnar crystal grains stand densely together on the surface of the long substrate;
forming a layer of a predetermined transition metal element on the surface of the magnesium diboride thin film and/or between the long substrate and the magnesium diboride thin film; and
diffusing the predetermined transition metal element preferentially into the grain boundary regions of the magnesium diboride columnar crystal grains by a heat treatment,
the predetermined transition metal element is an element having a body-centered cubic lattice structure.

15. The method for producing a magnesium diboride superconducting thin-film wire according to claim 14 , wherein the step of forming the magnesium diboride thin film includes a plurality of times of depositing magnesium diboride thin film layers to form a laminate structure made up of a plurality of layers.

16. The method for producing a magnesium diboride superconducting thin-film wire according to claim 15 , wherein the step of forming the magnesium diboride thin film further includes the step of depositing a transition metal element intermediate layer between the magnesium diboride thin film layers.

17. The method for producing a magnesium diboride superconducting thin-film wire according to claim 14 , wherein the predetermined transition metal element contains at least iron or manganese.

18. The method for producing a magnesium diboride superconducting thin-film wire according to claim 14 , wherein: the magnesium diboride thin film is formed under a vacuum at temperatures from 250° C. to 300° C. in the step of forming of the magnesium diboride thin film; and
diffusion heat treatment for the transition metal element is performed under a vacuum at temperatures from 300° C. to below 600° C. in the step of diffusing the predetermined transition metal element.

Assignees

• Hitachi Ltd

Inventors

• Doi Toshiya
• Horii Shigeru
• Kusunoki Toshiaki

Classifications

• H01F10/10

  characterised by the composition · CPC title

• H01F6/06 Primary

  Coils, e.g. winding, insulating, terminating or casing arrangements therefor · CPC title

• C01P2006/40

  Electric properties · CPC title

• C01B35/04 Primary

  Metal borides · CPC title

• H01F41/14

  for applying magnetic films to substrates · CPC title