High temperature phase transition in SOFC anodes based on Sr2MgMoO6−δ

The double perovskite Sr2MgMoO6−δ has been recently reported as an efficient anode material for solid oxide fuel cells (SOFCs). In the present work, this material have been investigated by high temperature X-ray diffraction (XRD), differential scanning calorimetry (DSC) and impedance spectroscopy to further characterise its properties as SOFC anode. DSC and XRD measurements indicate that Sr2MgMoO6−δ exhibits a reversible phase transition around 275 °C from triclinic (View the MathML sourceI1¯) with an octahedral tilting distortion to cubic (View the MathML sourceFm3¯m) without octahedral distortion. This phase transition is continuous with increasing temperature without any sudden cell volume change during the phase transformation. The main effect of the phase transformation is observed in the electrical conductivity with a change in the activation energy at low temperature. La3+ and Fe-substituted Sr2MgMoO6−δ phases were also investigated, however these materials are unstable under oxidising conditions due to phase segregations above 600 °C.