Electronic transport in the novel SOFC anode material La_1-xSr_x Cr_0.5Mn_0.5O_{3 δ}

Electronic conductivity in the potential SOFC anode material La1-xSrxCr0.5Mn0.5O3 +/-delta has been investigated in the range 0.2 < x < 0.3. log(sigma T) vs. 1/T plots indicate conduction via thermally activated polaron hopping. At 900 degrees C, conductivity in air increases with Sr2+ via an increase in [B;l 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(O-2), 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 +/-delta (c) 2006 Elsevier B.V. All rights reserved.