Defect chemistry and high-temperature thermodynamics of PrBaCo2O6-δ

•The model function log(pO2) = f(δ, T) can be extrapolated to lower temperatures.•The value of Δh-O was determined by direct oxidation of a sample in the calorimeter.•Both calculated and independently determined values of Δh-O coincide with each other.•Oxygen exchange impact on drop calorimetry meas...

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Veröffentlicht in:The Journal of chemical thermodynamics 2021-10, Vol.161, p.106523, Article 106523
Hauptverfasser: Sednev-Lugovets, Anton L., Sereda, Vladimir V., Malyshkin, Dmitry A., Tsvetkov, Dmitry S., Ivanov, Ivan L., Zuev, Andrey Yu, Maignan, Antoine
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Sprache:eng
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Zusammenfassung:•The model function log(pO2) = f(δ, T) can be extrapolated to lower temperatures.•The value of Δh-O was determined by direct oxidation of a sample in the calorimeter.•Both calculated and independently determined values of Δh-O coincide with each other.•Oxygen exchange impact on drop calorimetry measurements was assessed.•The values of Cp(T),Δ298.15THo and Δ298.15TSo for PrBaCo2O5.77 were calculated. Using the drop calorimetry and differential scanning calorimetry (DSC), the enthalpy increments of pure PrBaCo2O6-δ 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 pO2, but variable oxygen content in PrBaCo2O6-δ (isodynamical conditions). The defect structure analysis yielded the analytical expressions for the equilibrium oxygen partial pressure, log(pO2) = f(δ, T), and the partial molar enthalpy of oxygen, Δh¯O = f(T, δ) in PrBaCo2O6-δ, both functions being valid in relatively wide temperature range. The value of Δh¯O at 1273 K was assessed independently by means of direct oxidation of PrBaCo2O6-δ in the DSC setup, and was found to agree well with Δh¯O calculated from the defect structure model and pO2 – T – δ diagram. The knowledge of Δh¯O = f(T, δ) allowed recalculating the enthalpy increments for the sample with constant oxygen content, Δ298.15TH∘(PrBaCo2O5.77), which were fitted with a modified Einstein function. The smoothed values of Δ298.15TH∘, heat capacity Cp(T), and entropy increments Δ298.15TS∘ were evaluated and tabulated for PrBaCo2O5.77 in the temperature range 350 ≤ T/K ≤ 1300. The results obtained can be used for calculating Δ298.15TH∘, Cp(T), and Δ298.15TS∘ for PrBaCo2O6-δ with an arbitrary constant oxygen content.
ISSN:0021-9614
1096-3626
DOI:10.1016/j.jct.2021.106523