Defect chemistry and charge transport in LaSr3Fe3− x Mo x O10− δ

Molybdenum containing solid solution LaSr₃Fe_3−xMo_xO_10−δ with triple-layer Ruddlesden-Popper structure is considered a promising mixed conducting material for high-temperature electrochemical applications. Oxygen content and electrical conductivity in the compositions with x=0.1 and 0.2 were measured in the range of oxygen partial pressure from 10⁻²⁰ to 0.5 atm at temperatures 750-950°C. Experimental data were employed for the simulation of defect equilibrium and charge transfer in oxides. The defect distribution over two B-sublattices and four anion sublattices was determined depending on oxygen partial pressure and temperature. The main transport pathways of electrons, holes, and oxygen ions were found to be spatially separated in these oxides between B1, B2, and O4 sublattices, respectively. An increase in the molybdenum content was found to result in higher electron and oxygen ion conductivity. The enhancement of electron conductivity is explained by partial molybdenum reduction and involvement of Mo⁵⁺ ions in electron transport. As for ion conductivity, its improvement is suggested to be attributed to oxygen mobility increase due to a decrease in a fraction of tetrahedrally coordinated iron ions in the B1 sublattice and respective vacancy disordering in the O4 sublattice.