Study of the Phase Stability of La_0.6Sr_0.4MnO_{3 – δ} Oxide with Mixed Oxygen–Electronic Conductivity

This work is devoted to the study of thermodynamic characteristics and phase stability of oxides with a perovskite structure using both classical and original methods for the studying of compounds with similar composition. An oxide with mixed oxygen–electronic conductivity La_0.6Sr_0.4MnO_{3 – δ} obtained by solid-state synthesis was chosen as object of research. The stoichiometric range of this composition has been established at temperatures of 600–900°C in the region of oxygen partial pressure up to 3 × 10^–4 atm. The chemical potential of oxygen in the gas phase is calculated, as well as the dependences of the oxygen partial molar enthalpy and entropy in the oxide in the nonstoichiometry range δ = 0.01–0.012.