Role of SrMoO4 in Sr2MgMoO6 synthesis

Here we investigate the elemental and phase compositions during the solid-state synthesis of the promising SOFC-anode material, Sr2MgMoO6, and demonstrate that molybdenum does not notably evaporate under the normal synthesis conditions with temperatures up to 1200 °C due to the formation of SrMoO4 as an intermediate product at low temperatures, below 600 °C. However, partial decomposition of the Sr2MgMoO6 phase becomes evident at the higher temperatures (∼1500 °C). The effect of SrMoO4 on the electrical conductivity of Sr2MgMoO6 is evaluated by preparing a series of Sr2MgMoO6 samples with different amounts of additional SrMoO4. Under the reducing operation conditions of an SOFC anode the insulating SrMoO4 phase is apparently reduced to the highly conductive SrMoO3 phase. Percolation takes place with 20–30 wt% of SrMoO4 in a Sr2MgMoO6 matrix, with a notable increase in electrical conductivity after reduction. Conductivity values of 14, 60 and 160 S/cm are determined at 800 °C in 5% H2/Ar for the Sr2MgMoO6 samples with 30, 40 and 50 wt% of added SrMoO4, respectively.