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The electrical conductivity of perovskite-type Sr1–xCexFeO3–δ(x= 0.05, 0.10, and 0.15) was measured in the range of oxygen partial pressure from 10–19to 0.5 atm at temperatures 750–950 °C. The results were analyzed using the concentration of iron and cerium ions in different oxidation states derived from the pO2–T–δ diagrams of these compositions by thermodynamic analysis of defect equilibrium. Three models assuming different involvements of cerium and iron in electron transport in addition to hole and oxygen-ion conductivity were used for the simulation of electrical conductivity data. The best fit to the experimental data was obtained in the model, suggesting a minor contribution of electrons localized on cerium ions to conductivity via a separate network with low carrier mobility. The averaged mobility values for holes, electrons, and oxygen ions can be indicated for all compositions as 0.04, 5 × 10–3, and 1 × 10–5cm2V–1s–1with activation energies of 0.17, 0.5, and 0.7 eV, respectively. An increase in the cerium content in Sr1–xCexFeO3–δfrom 0.05 to 0.15 was found to result in an almost 10-fold decrease in ion conductivity, which is attributed to a decrease in the mobility of oxygen ions, whereas it has an insignificant effect on hole and electron conductivity.

The conductivity of the entire solid solution La 1− xSr xFeO 3−δ, where x=0.2, 0.4, 0.5, 0.7 and 0.9, in the oxygen partial pressure range 10 −19 to 0.5 atm and temperatures between 750 and 950 °C is reported. The analysis of the isothermal pressure dependences of the conductivity reveal that the lanthanum-strontium ferrites can be characterized as mixed ion-electron conductors in the low-oxygen pressure/high-oxygen deficiency limit. The partial contribution to conductivity from oxygen ions increases with strontium content and attains a maximal value at x=0.5. Further increase in doping results in the development of oxygen vacancy ordering phenomena and deterioration of the conducting properties.

The electrical properties of perovskite-related oxide La_0.3Sr_0.7Fe_{1 - x}Ga_xO_{3 − δ} (x = 0–0.5) are reported within the temperature range 750 to 950 °C and the oxygen partial pressure range between 10⁻¹⁹ and 0.5 atm. The maximum solid solubility of gallium in the iron sublattice of La_0.3Sr_0.7FeO_{3 − δ} is close to 30%. At oxygen pressures about 10⁻⁴ atm, the materials undergo a transition from perovskite to oxygen vacancy ordered structures. The type of vacancy ordering depends on gallium content. Both p- and n-type electronic conductivities decrease when insulating gallium cations having stable oxidation state are incorporated into the iron sublattice of the ferrite. The observed temperature and oxygen pressure dependencies of the p-type electronic conductivity in the ordered phases suggest a transition from the intrinsic regime, when the electron–hole conduction is governed by the band gap, to the extrinsic regime, controlled by the amount of the oxygen excess in the vacancy ordered structure. The ordered strontium–lanthanum ferrite was shown to be a mixed conductor with oxygen ionic conductivity of about 0.1 S cm⁻¹ at 900 °C. Ionic conduction in the vacancy ordered phases decreases with increasing gallium concentration.

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