Abstract
A defect equilibrium model for PrBaCo 2 O 5+ δ is suggested based on oxygen non-stoichiometry data. The model includes reactions of oxygen exchange and charge disproportionation of Co 3+ cations. The respective equilibrium constants, enthalpies and entropies for the reactions entering the model are obtained from the fitting of the experimental data for oxygen non-stoichiometry. The enthalpies of oxidation Co 2+ →Co 3+ and Co 3+ →Co 4+ are found to be equal to 115±9 kJ mol –1 and 45±4 kJ mol –1 , respectively. The obtained equilibrium constants were used in order to calculate variations in concentration of cobalt species with non-stoichiometry, temperature and oxygen pressure. Variations in concentration of cobalt species with oxygen content in PrBaCo n 2 + Co z 3 + Co p 4 + O 5 + δ at 650 °С. • The defect equilibrium model based on oxygen non-stoichiometry data is suggested. • Disproportionation of Co 3+ cations gives significant contribution to defect equilibrium. • The hole concentration obtained from the model is in accord with electrical properties.
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