OXIDATION OF YTTRIUM BARIUM CUPRATE YBA2CU3O6.09 UNDER POLYTHERMAL CONDITIONS

We studied the oxidation kinetics of YBa2Cu3O6.09 powders between 300 and 480 degrees C in an oxygen atmosphere (P-O2 = 10(5) Pa) at heating rates between 1 and 10 degrees C/min. In treating the experimental da ta, we used an approach based on the revaluation of nonisothermally ob tained data to isothermal conditions. The dependence of the activation energy of YBa2Cu3O6+x oxidation on oxygen stoichiometry x exhibits tw o bends (at 0.2 less than or equal to x less than or equal to 0.3 and 0.6 less than or equal to x less than or equal to 0.7), which are like ly to be associated with the ordering of oxygen ions in CuO2 planes.