Kinetic analysis of superconducting YBa₂O₇, by thermogravimetry in high vacuum

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 YBa₂Cu₃O_7-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, E_a, was 75 kJ mol^-1 and the frequency factor, A, was 3.0 × 10² s^-1.