Methods for producing Tl.sub.2 Ca.sub.2 Ba.sub.2 Cu.sub.3 oxide

Details Methods for producing Tl.sub.2 Ca.sub.2 Ba.sub.2 Cu.sub.3 oxide Methods for producing Tl.sub.2 Ca.sub.2 Ba.sub.2 Cu.sub.3 oxide

1991-10-10

1994-04-26

King, Roy

Superconductor technology: apparatus, material, process

Processes of producing or treating high temperature...

Coating

505730, 505731, 505742, 505783, 505501, 252521, 427 62, 4271263, 423624, 423635, 501123, H01L 3924, C01F 1102, C01G 1500

Patent

active

053066987

ABSTRACT:
Improved processes for making thin film and bulk thallium superconductors are described, as well as Tl superconductors having high critical current densities and low surface impedance. An annealing step in a reduced oxygen atmosphere is used to convert compounds containing thallium, calcium, barium and copper to a Tl-2223 superconducting phase or to convert an oxide having the nominal composition Tl.sub.2 Ca.sub.2 Ba.sub.2 Cu.sub.3 O.sub.x to a crystalline Tl-2223 phase. The oxygen pressure during annealing is controlled to be below the thermodynamic stability limit for conversion of Tl-2223 to Tl-2122 and secondary phases. Temperatures less than 880.degree. C. are used, the oxygen pressure being sufficient to prevent excess thallium loss so that the Tl content in the final Tl-2223 phase is Tl.sub.1.6-2.0. Electrical devices including SQUIDs can be made with these improved superconductors.

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