Recent progress in high-temperature superconducting materials

摘要

Since high-T_c superconducting materials werefirst discovered, there has been much research on materials, andseveral practical materials have been developed. It is remarkablethat Ag sheathed Bi types have reached the application stage andsuperconducting magnets which generate 7 T at 20 K have beenrealized. Various small scale electric power systems using theseBi tape conductors are now being developed. However, becauseof the low critical field (irreversible field) at 77K, theapplications are limited, and development of next-generationconductors with large current carrying capability even at 77K instrong fields are desired. For bulk materials, the trapped field hasreached 2.1 T at 77K. nevertheless, further improvements in thetrapped field and other characteristics are required for actualapplications such as flywheel-type electric power storage systems.In this review, the describe several basic problems in realizingpractical conductors and bulk materials, and report on recentprogress in the fabrication processes of these materials and intheir applications.