Evaluation of electrical conductivity and oxygen diffusivity of the typical Ruddlesden-Popper oxide Sr3Fe2O7-δ

The electrical conductivity (σ) and oxygen diffusivity of the typical Ruddlesden-Popper oxide Sr3Fe2O7-δ were investigated with the variation of oxygen partial pressure, P(O2), and temperatures, and thus the results were discussed based on its defect structure. The σ increases with the increase of P(O2) and a positive slope of log σ depend on P(O2) is close to 1/4 with the small polaron conduction, where the mobility μP are between 0.01 and 0.02 cm2 V−1 s−1 regardless of temperature and P(O2). Oxygen diffusivity derived from the electrical conductivity relaxation (ECR) after an abrupt change of P(O2) increased with the increase P(O2) and temperature. A new pulse isotope 18O-16O exchange (PIE) at 623-773 K was carried in order to rapidly determine the tracer oxygen surface reaction coefficient. The numerical relationship of oxygen diffusivity measured by ECR and PIE measurements was successfully established by the ambipolar diffusion theory and defect chemical analysis.