A transient thermogravimetric study on the oxygen permeation at high temperature of the superconducting material YBa2Cu3O7-δ

The solid-gas phase oxygen ions exchange of the superconducting material YBa2Cu3O7-delta (YBCO) powder at high temperature subject to an instantaneous change of surrounding gas between pure oxygen and nitrogen was studied by a transient thermogravimetric analysis (TGA) method. The dependence of equilibrium oxygen vacancy of YBCO sample on surrounding partial oxygen pressure at temperature region 500-800 degreesC was measured by a homemade static oxygen absorption instrument. A rapid weight gain in the oxygen absorption period and a slow weight loss in the oxygen desorption period were observed in the transient experiment. The surface reaction rate constants both for the oxygen absorption and desorption periods were calculated by considering the surface reaction as the rate-limiting step. The result shows that rate constant for the oxygen desorption period is much smaller than that of the oxygen absorption period. (C) 2004 Published by Elsevier B.V.