Preparation Properties and Applications of Large Bulk Superconductors by Quench and Melt Growth Process

Large bulk YBaCuO superconductors prepared by melt processes exhibit unique macro properties such as strong repulsion of a permanent magnet and high magnetic flux density trapping. These properties are explained by the total pinning force of the bulk. Since sintered polycrystalline bulk materials include many weak links such as grain boundaries, the total pinning force is weak. As melt-processed bulk materials have much less number of grain boundaries, the total pinning force increases. These properties were further improved by elimination of grain boundaries in the large bulk superconductors. This was enabled by additional techniques to the melt processes such as seeding and unidirectional growth. Applications of the bulk superconductors have been proposed such as non-contact transportation bulk magnets and bearings. Although the possibility of these applications is not clear, the future of the bulk superconductors is expected to be hopeful.