Defect chemistry and high-temperature thermodynamics of PrBaCo2O6-δ

Using the drop calorimetry and differential scanning calorimetry (DSC), the enthalpy increments of pure PrBaCo2O6-delta double perovskite in air in the temperature range from 365.3 K to 1272.8 K were obtained. As-measured enthalpy increments corresponded to the constant pO(2), but variable oxygen content in PrBaCo2O6-delta (isodynamical conditions). The defect structure analysis yielded the analytical expressions for the equilibrium oxygen partial pressure, log(pO(2)) = f(delta, T), and the partial molar enthalpy of oxygen, Delta h(0) = f(T, delta) in PrBaCo2O6-delta, both functions being valid in relatively wide temperature range. The value of Delta h(0) at 1273 K was assessed independently by means of direct oxidation of PrBaCo2O6-delta in the DSC setup, and was found to agree well with Ah o calculated from the defect structure model and pO(2) - T - 6 diagram. The knowledge of Delta h(0) = f(T, delta) allowed recalculating the enthalpy increments for the sample with constant oxygen content, Delta H-T(298.15)degrees(PrBaCo2O5.77), which were fitted with a modified Einstein function. The smoothed values of Delta H-T(298.15)degrees, heat capacity C-p(T), and entropy increments Delta S-T(298.15)degrees were evaluated and tabulated for PrBaCo2O5.77 in the temperature range 350 <= T/K <= 1300. The results obtained can be used for calculating Delta H-T(298.15)degrees, C-p(T), and Delta S-T(298.15)degrees for PrBaCo2O6-delta with an arbitrary constant oxygen content. (C) 2021 Elsevier Ltd.

Automated summary

The study utilized drop calorimetry and differential scanning calorimetry to investigate the enthalpy increments of PrBaCo2O6-delta double perovskite at various temperatures, yielding valuable analytical expressions and findings for the equilibrium oxygen partial pressure and partial molar enthalpy of oxygen. These results can be used to calculate thermodynamic properties for PrBaCo2O6-delta with different oxygen content.