Superconductor technology: apparatus – material – process – High temperature – per se – Having tc greater than or equal to 150 k
Patent
1990-12-20
1992-03-31
Roy, Uprendra
Superconductor technology: apparatus, material, process
High temperature , per se
Having tc greater than or equal to 150 k
1566171, 156621, 427 62, 505736, H01L 3900
Patent
active
051008700
ABSTRACT:
Disclosed is a broadly applicable method for making an article that, exemplarily comprises a superconductive oxide body, including a thin layer on a substrate, or powder particles. In a preferred embodiment, the method comprises forming a precursor melt and contacting at least a part of the melt with oxygen such that the concentration of oxygen in the part of the melt increase to a critical concentration, resulting in formation of the desired oxide, substantially without drop in temperature. The precursor melt comprises at least one metallic element M, and at least the part of the melt is at a temperature T, with T.sub.m <T<T.sub.o, where T.sub.m is the freezing temperature of the melt and T.sub.o is the melting temperature of the superconductive oxide. In an exemplary embodiment the melt consists essentially of Yb, Ba, and Cu in 1:2:3 atomic ratio, T is about 900.degree. C. A layer of superconductive oxide on a Sr-TiO.sub.3 substrate is formed by dipping the hot (900.degree. C.) substrate into the melt, exposing the melt-coated substrate to oxygen such that oxygenation and solidification of the coating results, and furnace cooling the coated substrate in oxygen. The thus produced coating has composition YbBa.sub.2 Cu.sub.3 O.sub.9-.delta. (.delta..about.2.1), is essentially single phase, strongly textured, has T.sub.c of about 85K and J.sub.c of about 3.times.10.sup.4 A/cm.sup.2. An aspect of the invention is the fact that the precursor melt need not be stoichiometric. For instance, we have formed a layer of composition YbBa.sub.2 Cu.sub.3 O.sub.7 from a melt of composition Yb.sub.2 BaCu. The inventive technique can produce compositionally essentially homogeneous material. It is readily adaptable to produce ceramics (including high T.sub.c superconductors) and other materials (e.g., A1N) in a variety of shapes (including wire tape, and powders) by a variety of techniques (including continuous processing). The inventive method can also be used to form a superconductive bond between two pre-existing ceramic superconductive bodies.
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Chen Ho S.
Indig George S.
Kimerling Lionel C.
AT&T Bell Laboratories
Pacher Eugen E.
Roy Uprendra
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