Oxygen content and thermodynamics of formation of double perovskites REBaCo2O6−δ (RE = Gd, Pr)

• ΔfHi∘ of REBaCo2O6−δ (RE = Gd, Pr) at 298 K were determined as a function of oxygen nonstoichiometry.
• ΔfHGdBaCo2O6−δ∘ and ΔfHPrBaCo2O6−δ∘ were found to increase linearly with oxygen nonstoichiometry.
• Thermodynamic stability of the double perovskites decreases with oxygen nonstoichiometry.

Standard enthalpies of formation of double perovskites REBaCo2O6−δ (RE = Gd, Pr) from elements, ΔfHi∘, at 298 K were determined as a function of their oxygen content using isothermal solution calorimetry. ΔfHGdBaCo2O6−δ∘ and ΔfHPrBaCo2O6−δ∘ were found to increase linearly with oxygen nonstoichiometry. Such behavior indicates in favor of decrease of relative thermodynamic stability of the double perovskites with oxygen nonstoichiometry.