Oxygen nonstoichiometry in Pr1−xSrxCo0.2B0.8O3−δ (B = Mn, Fe, x = 0.2, 0.4) perovskite oxides

Thermogravimetric analysis was applied to the study of oxygen nonstoichiometry of perovskite oxides of the compositions Pr0.8Sr0.2Co0.2Mn0.8O3−δ and Pr1−xSrxCo0.2Fe0.8O3−δ (x = 0.2, 0.4). The measurements were performed in the temperature range from room temperature to 1200 °C in various atmospheres: oxygen, air and argon. The recorded weight loss corresponds to the loss of lattice oxygen. The magnitude of oxygen loss increased and the temperature at which oxygen loss became significant decreased with increasing Sr content. The loss of lattice oxygen became more significant as the oxygen partial pressure decreased. For the same pO2 and level of Sr doping, the Fe-containing composition became more easily oxygen deficient than the corresponding Mn-containing one, suggesting that Fe is more resistant to oxidation from the trivalent to the tetravalent state than Mn. Electrical conductivity measurements, performed in air, showed that the temperature ranges at which conductivity decrease was observed, correspond fairly well with those ranges where weight loss was detected.