Optimization of Sintering and Metallurgical Studies on the Bi-Sr-Ca-Cu-O Superconductors
Morphology, superconducting properties, possibility of orientation of the grains, workability and so on have been studied for the Bi-Sr-Ca-Cu-0 system. Tapes and wires as well as bulk (pellet) specimens have been prepared. The results of the thermogravimetric analysis indicated that the phase transformation which accompanies absorption of oxygen does not occur in this material from ~86O°C down to 400°C. Tape specimens prepared by a combination of cold work and sintering showed J of 1100A/cm2 at 77K with a good reproductivity. In these tape specimens, c axis of the grains tends to align perpendicularly to the tape surface. A 1330-filament Bi-Pb-Sr-Ca-Cu-0 wire with a Ag matrix has been successfully fabricated. This multifilamentary wire showed high-T transitions when sintered at relatively low temperature (840°C). It has turned out that the concentration of Pb in the oxide must be controled (reduced) before the packing into a Ag sheath for the superconducting phase to be formed in a long wire. The results of this study indicate that the Bi-Sr-Ca-Cu-O system material has an advantage over other oxide superconductors with respect to practical use.
KeywordsOxide Powder Superconducting Phase Bulk Specimen Longitudinal Cross Section Oxide Superconductor
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