Electronic transport in the novel SOFC anode material La1−xSrxCr0.5Mn0.5O3±δ

Electronic conductivity in the potential SOFC anode material La1−xSrxCr0.5Mn0.5O3±δ has been investigated in the range 0.2 < x < 0.3. log(σT) vs. 1/T plots indicate conduction via thermally activated polaron hopping. At 900 °C, conductivity in air increases with Sr2+ via an increase in [BB] holes (B—transition metal). X-ray absorption spectroscopy (XAS) studies indicate that compensation for A-site Sr substitution and oxygen vacancy formation is via the Mn cation only; Cr maintains a 3+ oxidation state and 6-fold oxygen coordination. Electronic transport occurs by percolation between Mn cations in a disordered B-site sub-lattice. Conductivity decreases with p(O2), which is indicative of p-type conduction behaviour, but the relationship cannot be explained by a simple redox equilibrium involving Mn3+, Mn4+ and oxygen, possibly due to co-existence of Mn2+, Mn3+ and Mn4+ via disproportionation as with La1−xSrxMnO3±δ.