Fabrication of Y-Ba-Cu-O superconductor for magnetic bearing

Although high-T_c oxide superconductors, such as Y-Ba-Cu-O, should have great potential for application to repulsive magnetic bearings, various kinds of improvements on the mechanical and electrical properties of the materials are needed. The authors tried to improve these properties by changing compression pressure in the process used in forming a pellet systematically and by adding Ag powder to Y-Ba-Cu-O powder. All materials used here were confirmed as Y₁Ba₂Cu₃O₇ by X-ray diffraction analysis. It was found that density, hardness, temperature of zero resistance, and ratio of resistivity at a temperature of 300 K and that at a temperature of 100 K increase as the compression pressure becomes higher. On the other hand, a temperature of resistance drop and a repulsive force due to the Meissner effect were insensitive to the pressure. The Ag content in the pellets makes the temperature of zero resistance higher. It was also found that the ratio of resistivity had possible use as a criterion for better superconductive characteristics