The thermodynamic properties of weakly bound oxygen and electron transport in Sr3Fe2O6+δ under oxidizing conditions

The content of oxygen, electrical conductivity, and thermal electromotive force were measured for ferrite Sr₃Fe₂O_6+δ over the oxygen partial pressure range 10^?4–0.5 atm at 650–950°C. The partial molar thermodynamic functions of weakly bound oxygen in the oxide structure were determined. Labile oxygen ions were characterized as an ensemble of weakly interacting particles. The predominant charge carriers under experimental conditions were electron holes. An analysis of conductivity was performed using the data on the oxygen content. The concentration, activation energy, and mobility of charge carriers were determined. The results can be satisfactorily interpreted using the polaron transfer model of conductivity taking into account the charge disproportionation reaction for iron ions, 2Fe⁴⁺ = Fe³⁺ + Fe⁵⁺.