Electronic conduction mechanism and defect chemical model of LaNi_0.4Fe_0.6O_{3 − δ}

In order to elucidate the electronic conduction mechanism and defect chemical model of LaNi_0.4Fe_0.6O_{3 − δ} at high temperatures, electrical conductivity (σ), Seebeck coefficient (S), and oxygen vacancy concentration (δ) of LaNi_0.4Fe_0.6O_{3 − 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 LaNi_0.4Fe_0.6O_{3 − 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 LaNi_0.4Fe_0.6O_{3 − δ} can be explained.