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

摘要

The most important property affecting the usefulness high-T/sub c/ superconductors is the critical current density. With wire applications in mind, three kinds of fabrication process, solid reaction, film, and melt, were studied to improve the transport critical current densities (J/sub c/) at liquid nitrogen temperatures (77.3 K). In all three processes, 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, J/sub c/ of 4 *10/sup 6/ A/cm/sup 2/ was obtained by fabricating films with a flat surface 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. Magnetic field dependencies of the J/sub c/ of each sample were studied. Thin films of YBaCuO maintained the value of 10/sup 4/ A/cm/sup 2/ even in 20 T.