Oxygen stoichiometry and mixed ionic-electronic conductivity of Sr1−aCeaFe1−bCobO3−x perovskite-type oxides

The structure, oxygen stoichiometry, total and ionic electrical conductivities of Sr1−aCeaFe1−bCobO3−x (a=0÷0.2, b=0÷1.0) were investigated. XRD patterns show the cubic perovskite structure of all air-treated samples. In reducing atmosphere the Co rich compositions were partially decomposed. The change of the lattice parameter a with Ce content could be explained on the basis of the oxygen stoichiometry values, determined by solid electrolyte investigations. The total conductivity (p-type, above 400–800°C changing to metallic-like behaviour) was enhanced by the Co content and reached 200 S cm−1 at 600°C. From permeation measurements an ionic conductivity higher than YSZ and for the compositions of lower ceria content as high as gadolinia doped ceria was observed. The results are compared with those of La1−aSraFe1−bCobO3−x and of manganites.