Superconducting YBa2Cu3O7, was subjected to high vacuum thermogravimetry (TG) at various heating rates in the range from room temperature to 1000°C. Two distinct weight-loss steps, each of which corresponds to the evolution of almost 1/202, were observed on the TG curve. The product following the first step was apparently the non-stoichiometric compound YBa2Cu3O7-δ. The rate equation for the first step was dδ/dt = k(1-δ); the corresponding specific rate constant, k, was 1.8 × 10-3 s-1 at 490°C, the activation energy, Ea, was 75 kJ mol-1 and the frequency factor, A, was 3.0 × 102 s-1.
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