The Phase Decomposition of YBa2Cu3O6.9 Induced by HIP

Abstract

Phase stability of the high-T _c oxide YBa₂Cu₃O_6.9 (1-2-3 phase) has been studied under the pressure generated by canned HIP at various temperatures. Resistivity measurements in samples hipped at 930°C and 780°C show a degradation of electric properties, for example the broad transition at T _c and the rise in resistivity above T _c. The sample hipped at 830°C exhibits a sharp transition at a T _c of 80 K and low resistivity above T _c. X-ray analysis reveals that the original compound decomposes into the 2-1-1 phase in parts in the former, and into the 1-2-4 and 2-1-1 phases in the latter. This phase decomposition is explained by the rise in oxygen partial pressure during HIP.