Method for producing a rotationally symmetrical molded part of a

Details Method for producing a rotationally symmetrical molded part of a Method for producing a rotationally symmetrical molded part of a

1993-09-22

1995-04-25

Fiorilla, Christopher A.

Superconductor technology: apparatus, material, process

Processes of producing or treating high temperature...

With melting

264 82, 264270, 264311, 505490, 505492, 505500, H01L 3912, B28B 120

Patent

active

054098912

ABSTRACT:
A rotationally symmetrical molded part of a high-temperature superconductor achieves a critical current density of j.sub.c .gtoreq.800 A/cm.sup.2 at a temperature of 77K, by using a powder mixture (8) having the stoichiometric composition of Bi.sub.2+x EA.sub.3 Cu.sub.2 O.sub.y, where -0.15<x<0.4; EA=an alkaline earth metal or a mixture of alkaline earth metals, in particular a mixture of Sr and Ca in the ratio of Sr:Ca=(2+z):(1-z), where 0<x<0.2; 8.ltoreq.y.ltoreq.8.3. With the aid of a conveying chute (9), the powder mixture (8) is brought uniformly at room temperature with a grain size of <50 .mu.m into a silver mold (5) which is arranged inside a rotating fusion mold (4), open at one side, in a furnace (3). Subsequently, the fusion mold (4) is accelerated, heated to 500.degree. C. and held for approximately 30 min at 500.degree. C. After subsequent partial melting at a temperature of T.sub.m K to T.sub.m +6K, where T.sub.m =melting temperature of the pulverulent starting material, for 30 min to 2 h at an oxygen partial pressure of p(O.sub.2).gtoreq.0.8 bar, a first long-term annealing is performed at 840.degree. C. to 850.degree. C. for 20 h to 40 h. Thereafter, a second long-term annealing is performed at a reduced oxygen partial pressure of p(O.sub.2) and, below 700.degree. C., cooling to room temperature in a nitrogen atmosphere. There can be a subsequent third long-term annealing.

REFERENCES:
patent: 4632686 (1986-12-01), Brown et al.
patent: 5151407 (1992-09-01), Provenzano et al.
"Phase Relations and Alignment in Bismuth-Based Tc Wires", Hellstrom, JOM, Oct. 1992, pp. 48-53.
JP 2-192615 A: in Derwent, Ref. 90-272081/36.
JP 2-145423 A: in Derwent, Ref. 90-214336/28.
JP 1-163919 A: in Derwent, Ref. 89-229968/32.

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