Defect structure and charge transfer in the double perovskite GdBaCo2O6 − δ

The results of oxide ion and total conductivity, and Seebeck coefficient measured as a function of oxygen partial pressure, pO2, in temperature range 820 ≤ T °C ≤ 1070 are presented for GdBaCo2O6 − δ with double perovskite structure. Data on Seebeck coefficient as a function of oxygen nonstoichiometry, δ, was successfully described on the basis of the defect structure model proposed for this compound earlier. Mobilities of charged defect species were calculated using data on total conductivity and pO2–T–δ   diagram. Thermodynamic enhancement factor, W=−∂lnpO2∂lnVO
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• T, was shown to have a maximum at δ = 1. This was explained by the change of order degree of oxygen sublattice of GdBaCo2O6 − δ. Activation energy of oxide ion conductivity was found to come to value of 0.96 ± 0.06 eV and that of oxygen vacancies mobility varies within the range 0.53–0.78 eV depending on oxygen nonstoichiometry.