Exploring the defect equilibrium and charge transport in electrode material La0.5Sr0.5Fe0.9Mo0.1O3-δ.

Abstract

Perovskite-type La0.5Sr0.5Fe0.9Mo0.1O3-δ synthesized via glycine nitrate combustion and sintered at 1350 °C was found to have an orthorhombic lattice, which transforms upon heating into a rhombohedral and then a cubic one. The oxygen content and electrical conductivity in this oxide were measured in the range of oxygen partial pressures from 10-20 to 0.5 atm at 750-950 °C by coulometric titration and four-probe dc techniques, respectively. The oxygen content data were used to model the defect equilibrium in the oxide. Oxidation, charge disproportionation and electron exchange reactions between iron and molybdenum were assumed by the model to be involved in the formation of defects. The experimental data were well approximated with the model and the concentrations of charge carriers in La0.5Sr0.5Fe0.9Mo0.1O3-δ were determined to be used for the electrical conductivity analysis. The average mobility of oxygen ions and n- and p-type charge carriers was determined to be about 10-5, 0.007, and 0.07 cm2 V-1 s-1 with an activation energy of 0.80 ± 0.02, 0.34 ± 0.01, and 0.23 ± 0.01 eV, respectively. Comparison with La0.5Sr0.5FeO3-δ shows that 10% Mo substitution provides a substantial increase in both the concentration and mobility of n-type carriers, which results in an almost threefold increase in electron conductivity under reducing conditions, while maintaining a high level of ionic conductivity.