RELAXATION OF DEFECTS INTRODUCED INTO YBA2CU3O7-X BY MECHANICAL MILLING

YBa2Cu3O7-x compound (T-C = 90 K) was milled in a rotary mill for up t o 30 h. Study of the thermal behaviour by differential scanning calori metry revealed one exothermic peak in the temperature interval up to 4 00 degrees C with the highest rate of heat release at T-max. The therm al effect increased with the time of milling. The shift of T-max with different heating rates (beta) was measured for the rates 5, 10, 20 an d 40 degrees C min(-1). The linear dependence In (beta/T-max(2)) versu s 1/T-max is typical for an Arrhenius process. The determined activati on energy of heat release E = 1.32-1.67 eV (127.36-161.13 kJ mol(-1)) corresponds to the activation energy of atomic oxygen diffusion in the YBa2Cu3O7-x lattice. Therefore this effect is related to the defect r elaxation through diffusive redistribution of oxygen atoms.