Abstract
The compound Ba0.6Sr0.4Co0.8Fe0.2O3−δ with perovskite structure has been studied focusing mainly on the thermodynamic stability in correlation to the change in the oxygen stoichiometry. The thermochemical behavior has been investigated from room temperature to 1300K by thermal gravimetry and differential thermal analysis in air and by calorimetry in scanning mode in Argon. The temperature dependence of enthalpy (ΔHT298) in the temperature range of 300–900K was measured by drop calorimetry. Thermodynamic properties represented by the relative partial molar free energies, enthalpies and entropies of oxygen dissolution in the perovskite phase, as well as the equilibrium partial pressures of oxygen have been obtained in the temperature range of 823–1273K using solid electrolyte electrochemical cells (EMF). The influence of the oxygen stoichiometry on the thermodynamic properties was examined using a coulometric titration technique coupled with EMF measurements. The results are discussed based on the strong correlation between the energetic parameters and the charge compensation of the material system.
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