Method and composition for improving flux pinning and critical current in superconductors
AssigneeThe Regents of the University of California
InventorDonald E. Morris
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Abstract
Superconducting materials and methods of forming superconducting materials are disclosed. Highly oxidized superconductors are heated at a relatively high temperature so as to release oxygen, which migrates out of the material, and form a non-superconducting phase which does not diffuse out of grains of the material. The material is then reoxidized at a lower temperature, leaving the non-superconducting inclusions inside a superconducting phase. The non-superconducting inclusions act as pinning centers in the superconductor, increasing the critical current thereof.
Claims14
A method of using a high temperature superconductor in a magnetic field, the high temperature superconductor comprising a material selected from the group of Re-Ba-Cu-O, Y-Ba-Cu-O, Bi-Sr-Ca-Cu-O, Ba-K-Bi-O, Tl-Ba-Ca-Cu-O, and combinations thereof, said high temperature superconductor formed by heating a starting material at a sufficient temperature and with a low enough oxygen partial pressure to cause localized areas within the starting material to become unstable and decompose into non-superconducting phases, wherein said temperature and oxygen partial pressure do not permit significant diffusion of said localized areas of non-superconducting phases to oxide superconductor grain boundaries, wherein said non-superconducting phase lies substantially along parallel crystallographic planes within the high temperature superconductor, the method comprising the step of orienting said superconductor in a magnetic field such that magnetic flux is substantially perpendicular to said parallel crystallographic planes of the non-superconducting phase, said high temperature superconductor having a higher critical current than said high temperature superconductor without said non-superconducting phase.
A method of precipitating a plurality of non-superconducting phase inclusions within a plurality of oxide superconductor grains, the method comprising the steps of:
- selecting a starting material from the group of oxide superconductors consisting of R.sub.1 Ba.sub.2 Ca.sub.3 O.sub.x, R.sub.1 Ba.sub.2 Cu.sub.4 O.sub.x, Bi.sub.2 Sr.sub.2 Ca.sub.2 Cu.sub.3 O.sub.x, and Tl.sub.2 Ba.sub.2 CaCu.sub.3 O.sub.x, wherein R is selected from the group consisting of yittrium and rare earth metals;
- heating the starting material at a sufficient temperature and with a low enough oxygen partial pressure to cause localized areas within the starting material to become unstable and decompose into non-superconducting phases, wherein said temperature and oxygen partial pressure do not permit significant diffusion of said localized areas of non-superconducting phases to oxide superconductor grain boundaries;
- halting the decomposition before all of said starting material has decomposed;
- and
- reoxidizing the starting material, wherein a plurality of non-superconducting phase inclusions remain trapped within a plurality of oxide superconductor grains.
Dependencies are inferred from the claim text.