EFFECT OF OXYGEN PARTIAL-PRESSURE ON DECOMPOSITION OF YBA2CU3O6.5+X AT HIGH-TEMPERATURES

A ceramic superconductor, YBa2Cu3O6.5+x, decomposes to liquid and Y2BaCuO5 at about 1280 K in air. In this study, effects of the oxygen partial pressure (P(O2)) on the decomposition were examined by means of powder X-ray diffraction analysis, thermal gravimetry and differential thermal analysis. The relation between P(O2) and the temperature of decomposition was obtained by the analysis of X-ray diffraction for the samples equibrated at various temperatures in various oxygen partial pressures, and was expressed in the equation of In (P(O2)/P-degrees) = - 113700/T+88.5[1218-1313 K. P-degrees = 101325 Pa]. The weight loss caused by the release of oxygen was also measured at the decomposition of YBa2Cu3O6.5+x under various oxygen partial pressures. The relation between x in YBa2Cu3O6.5+x and temperature when the decomposition occured was expressed as x = 0.00353 T - 5.08 [1218-1313 K]. The composition of the liquid formed by the decomposition was also determined.