Phase Decomposition of YBa₂Cu₃O_x and Behavior of Y₂O₃ at High Temperatures

抄録

YBa₂Cu₃O_x superconductors prepared by the sinter method were heated for various times at temperatures from 1273 to 2241 K in alumina, platinum and iridium crucibles, and then their contents were press-quenched between two copper plates. Phases formed in the press-quenched samples were indentified by means of SEM, EPMA and X-ray diffractometry. YBa₂Cu₃O_x decomposed into Y₂BaCuO₅. BaCuO₂ and an unknown phase at 1293 K. BaCuO₂ was unstable at higher temperatures than 1373 K. Y₂BaCuO₅ decomposed into Y₂O₃ and a liquid phase at 1423 K and Y₂O₃ was stable in the temperature range from 1423 to 2241 K. Iridium crucible was most useful for the heat treatment of the Y–Ba–Cu–O system at the high temperatures.