Conductivity and redox stability of double perovskite oxide SrCaFe1+xMo1-xO6-δ (x = 0.2, 0.4, 0.6)

A series of new double perovskite oxides SrCaFe1+xMo1-xO6-δ (x = 0.2, 0.4, 0.6) were synthesised by solid state reaction method. Synthesis of SrCaFe1+xMo1-xO6-δ (x = 0.2, 0.4, 0.6) were achieved above 700 °C in 5% H2/Ar, albeit with the formation of impurity phases. Introduction of calcium to Sr2Fe1+xMo1-xO6-δ (x = 0.2, 0.4, 0.6) was not successful in simultaneously improving the conductivity of these compounds, with a significant reduction in the formability observed with increasing calcium content. Phase stability upon redox cycling was not observed for SrCaFe1+xMo1-xO6-δ (x = 0.2, 0.4, 0.6). Redox cycling of SrCaFe1+xMo1-xO6-δ (x = 0.2, 0.4, 0.6) demonstrates a strong dependence on high temperature reduction to achieve high conductivities, with re-reduction at lower temperatures attaining between 0.1% and 58.4% of the initial conductivity observed after high temperature reduction. The conductivity of SrCaFe1.2Mo0.8O6-δ in 5%H2/Ar between 300 °C and 500 °C was around 73.5 Scm−1. The reliance of these compounds on high temperature reduction is expected to limit their utility as SOFC anode materials, as the vulnerability to oxidation can have disastrous consequence for fuel cell durability.