Measurement of electrical conductivity of La0.2Sr0.8Cr0.2Fe0.8O3-δ using gas-tight electrochemical cells

The oxygen partial pressure (pO2) dependence of the electrical conductivity of La0.2Sr0.8Cr0.2Fe0.8O3-δ (LSCrF) was obtained at T = 750–1060°C and pO2 = 10−18−0.5 atm. The slope of the plot of log σ vs. log pO2 is ∼1/5 in the p–type region, pO2 = 10−5−10−1 atm. The p-n transition pO2 increases with increasing temperature. The activation energy for ionic conduction was estimated to be 0.86 eV from an Arrhenius plot of the minimum conductivity vs. reciprocal temperature. At temperatures below 942°C, a plateau in the conductivity isotherm suggests the presence of a two-phase region. Most likely, phase separation occurs to form a mixture of a perovskite phase and an oxygen vacancy ordered phase related to brownmillerite.