Fabrication of oxide superconductors by melt growth method
AssigneeAT&T Bell Laboratories
InventorsSungho Jin, Richard C. Sherwood, Thomas H. Tiefel
Life of this patent
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Abstract
Superconductive oxide bodies such as wires, ribbons, rods, and other bulk bodies can be fabricated by a process that comprises melting precursor material, cooling at least of the melt such that a solid body of a desired shape results, and heat treating the solid body in an oxygen-containing atmosphere. The precursor material exemplarily is in the form of pressed superconductive oxide powder. The re-solidified superconductive material is relatively dense, typically textured, with relatively large grain size, and has improved properties, e.g., higher critical current density. An exemplary technique for melting of the precursor material is zone melting.
Claims18
A method of fabricating a body that comprises a superconductive oxide of nominal composition Ba.sub.2-x M.sub.1-y X.sub.x+y Cu.sub.3 O.sub.7.+-..delta., where M is selected from the group consisting of Y, Eu, La, and combinations thereof, the optional X is different from Ba and M and is selected from the group consisting of the elements of atomic number 57-71, Sc, Ca and Sr, with 0.ltoreq.x+y.ltoreq.1 and 0.ltoreq..delta.<0.5, and with Ba and M being at least 50% unsubstituted, wherein the method comprises
- (a) providing a quantity of precursor material comprising an oxide of one or more of Ba, Cu, M and X, associated with the precursor material is a phase diagram comprising a solid-liquid region and a liquid region, and a solidus temperature;
- (b) heating the precursor material such that at least a portion thereof is at a temperature above the solidus temperature and is a liquid;
- (c) cooling at least a part of the liquid precursor material to a temperature below the solidus temperature such that re-solidified precursor material results, the rate of cooling selected such that at least a substantial portion of the re-solidified precursor material comprises elongate grains, associated with a given elongate grain being a long axis and an aspect ratio, at least a substantial fraction of the elongate grains measuring at least about 10 .mu.m along the long axis and having an aspect ratio of at least 10:1;
- and
- (d) heat treating the re-solidified precursor material in an oxygen-containing atmosphere such that the superconductive oxide is produced from the re-solidified precursor material.
A method of fabricating a body that comprises a superconductive oxide of nominal composition Ba.sub.2-x M.sub.1-y X.sub.x+y Cu.sub.3 O.sub.7.+-..delta., where M is selected from the group consisting of Y, Eu, La, and combinations thereof, the optional X is selected from the group consisting of the elements of atomic number 57-71, Sc, Ca, and Sr, with 0.ltoreq.x+y.ltoreq.1 and 0.ltoreq..delta.<0.5, and with Ba and M being at least 50% unsubstituted;
- where the method comprises
- (a) providing a first body comprising a precursor material, the precursor material comprising an oxide of one or more of Ba, Cu, M and X;
- (b) heating the body such that a hot zone results, with at least a portion of the precursor material in the hot zone being a liquid and the precursor material not within the hot zone being solid;
- (c) moving the hot zone relative to the first body, such that directional solidification of liquid precursor material results, the solidification carried out such at least a substantial portion of the solidified precursor material comprises elongate grains, associated with a given elongate grain being a long axis and an aspect ratio, at least a substantial fraction of the elongate grains measuring at least 10 .mu.m along the long axis and having as aspect ratio of at least 10:1;
- and
- (d) heat treating the first body in an oxygen-containing atmosphere such that the superconductive oxide is produced from the directionally solidified precursor material.
A method of fabricating a body that comprises a superconductive oxide of nominal composition Ba.sub.2-x M.sub.1-y X.sub.x+y Cu.sub.3 O.sub.9-.delta., where M is selected from the group consisting of Y, Eu, and La, and X is one or more optional element different from Ba and M and selected from the group consisting of the elements of atomic number 57-71, Sc, Ca, and Sr, with 0.ltoreq.x.ltoreq.1 and 1.5<.delta.<2.5, with Ba and M being at least 50% unsubstituted, associated with the body being a critical current density;
- wherein the method comprises
- (a) providing a quantity of precursor material comprising an oxide of one or more of Ba, Cu, M and X, and producing a solid body from the precursor material;
- and
- (b) heat treating the solid body in an oxygen-containing atmosphere such that the solid body becomes a superconductive body;
- wherein the method further comprises
- (c) heating the precursor material such that at least a portion thereof becomes a liquid;
- and
- (d) cooling at least a part of the liquid precursor material such that the solid body results, the process carried out such that the superconducting body has a critical current density that is at least 20% larger than that of a comparison superconducting body of identical shape and composition that is produced by a method that does not involve melting of oxide precursor material.
Dependencies are inferred from the claim text.