OVERVIEW OF THE STATUS OF AND PROSPECTS FOR HIGH-TC WIRE AND TAPE DEVELOPMENT

Recent world-wide progress in the effort to develop long continuous lengths of conductor based on high-T(c) materials with high critical currents in substantial magnetic fields offers promise for a variety of applications. Two major problems, weak links and weak flux pinning, have plagued conductor development efforts from the beginning. Recent advances in mechanical processing of tape conductors based on BSCCO show great promise in overcoming weak links, with low-temperature J(c) values > 10(5) A/cm2 extending to magnetic fields > 25 T. Unfortunately, these materials continue to exhibit weak flux pinning at moderate temperatures for magnetic fields aligned along the crystalline c axis. This manifests itself in a J(c) that declines precipitously with magnetic field for T > 30 K. By contrast, conductors based on YBCO exhibit much stronger pinning at high temperature with smaller sensitivity to magnetic field orientation, but remain severely limited by weak links. The poor performance of BSCCO- and TBCCO-based materials appears to be strongly correlated with the high degree of intrinsic anisotropy. Phenomenological models describing this behavior and prospects for further progress are examined.