ELECTRICAL CONDUCTIVITIES OF SRFEO3-DELTA AND BAFEO3-DELTA PEROVSKITES

The conductivities and the Seebeck coefficients of the SrFeO3-δ and the BaFeO3-δ perovskites were measured in air, O2, and N2 in the temperature range from 650°C to room temperature. The carrier densities and the mobilities were calculated by using a small polaron hopping model. All the samples of the BaFeO3-δ show the hopping conduction, while the conductions of the SrFeO3-δ in air and O2 will be near metallic because the carrier densities and the mobilities are very large. The mobilities rather than the carrier densities decreased with the increase of the amounts of the oxygen vacancy, δ, in the range of 0 < δ < 0.5. The mobilities of SrFeO3-δ in which the FeOFe average distance is about 3.86 Å were about 103 times those of BaFeO3-δ with the FeOFe distance of 4.01 Å. Thus, the mobilities remarkably decreased with the increase of the FeOFe distance. It was concluded that the electrical conductivities of the SrFeO3-δ and the BaFeO3-δ at room temperature are mainly determined by the mobility which is affected by the oxygen vacancy and the FeOFe distance. © 1990.