Impact of Cerium Content on Ion and Electron Transport in Sr1–xCexFeO3–δ

The electrical conductivity of perovskite-type Sr 1– x Ce x FeO 3–δ ( x = 0.05, 0.10, and 0.15) was measured in the range of oxygen partial pressure from 10 –19 to 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 p O 2 – 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 –5 cm 2 V –1 s –1 with activation energies of 0.17, 0.5, and 0.7 eV, respectively. An increase in the cerium content in Sr 1– x Ce x FeO 3–δ from 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.