Critical current densities of high-T/sub c/ superconductors

While considering wire applications, three kinds of fabrication processes-solid reaction, film, and melt processes-were studied to improve the transport critical current densities (J/sub c/) of high-T/sub c/ superconductors at liquid nitrogen temperature (77.3 K). In all three processes, a J/sub c/ above 10/sup 4/ A/cm/sup 2/ was obtained without an applied magnetic field. In the solid reaction process, silver-sheathed BiPbSrCaCuO tapes with J/sub c/ of 12600 A/cm/sup 2/ were fabricated. The homogenization of the high-T/sub c/ phase (110 K), preferred alignment of the grains, and good contact at the grain boundaries resulted in the improvement of J/sub c/. In thin-film YBaCuO, a J/sub c/ of 4*10/sup 6/ A/cm/sup 2/, which is considered useful for practical application, was obtained by fabricating good films with flat surfaces and c-axis-oriented single-like crystals. In the melt process, oriented polycrystalline BiSrCaCuO rods with J/sub c/ of 14800 A/cm/sup 2/ were fabricated. The magnetic field dependencies of the J/sub c/ of each sample were studied. In particular, thin films of YBaCuO were found to maintain the value of 10/sup 4/ A/cm/sup 2/ even at 20 T.<
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