Electronic conduction mechanism and defect chemical model of LaNi0.4Fe0.6O3 − δ

In order to elucidate the electronic conduction mechanism and defect chemical model of LaNi0.4Fe0.6O3 − δ at high temperatures, electrical conductivity (σ), Seebeck coefficient (S), and oxygen vacancy concentration (δ) of LaNi0.4Fe0.6O3 − δ were measured as a function of oxygen partial pressure (p(O2)) and temperature. Relatively large σ and small positive S values are observed, which indicates the contribution of ionic conduction is negligibly small to thermoelectric power and the major electronic carrier is a hole. From the analysis of σ and S, it is expected that the LaNi0.4Fe0.6O3 − δ has small polaron hopping conduction mechanism where an electron is localized on the Fe. The slope of δ vs p(O2) shows a minimum value near the stoichiometric composition and the δ increases as p(O2) reduces and temperature increases. The relationship between δ vs. log p(O2) is analyzed by a localized electron model and the behavior of the oxygen nonstoichiometry of LaNi0.4Fe0.6O3 − δ can be explained.