Bulk Processing of High-Temperature Superconducting Oxides

Recent research and development activities related to processing of bulk superconducting oxides are reviewed. Wiring techniques in bismuth and thallium systems are already fairly well developed, allowing critical current densities to meet a required value for application at liquid helium temperature when a certain magnetic field is applied. In yttrium systems, pinning centers have been successfully introduced into the material even at liquid nitrogen temperature as a result of improvements in processing. Some applications utilizing this strong pinning force have been tested. The mechanism for growth of YBa2Cu3O7-d from the partially molten state has also gradually been clarified. In all three types of system, it is expected that superconducting wires with high critical current densities at liquid nitrogen temperature will be developed. A recently developed method for growing bulk single crystals is also mentioned briefly.