Microstructure and Critical Currents in High T sub c Superconductors

Recent investigations of microstructure and critical current behavior in various high T sub c superconductors such as Y-Ba-Cu-O, and Tl-Ba-Ca-Cu-O will be reviewed. In spite of the tremendous research effort, the progress toward major applications of the bulk high-temperature superconductors has been impeded by low critical currents and their severe deterioration in weak magnetic fields. Significant advances, however, have been made in understanding the causes of the problem as well as in improving the current-carrying capacity through proper microstructural control such as the melt-textured-growth in Y-Ba-Cu-O.