The structural and electrical properties of Sr2Ni0.75Mg0.25MoO6 and its compatibility with solid state electrolytes

The double perovskite Sr2Ni0.75Mg0.25MoO6 was evaluated as a potential anode material for intermediate temperature solid oxide fuel cells (IT-SOFCs). Its phase stability, electrical conductivity, thermal and chemical compatibility with perspective oxygen-ionic (Zr0.85Y0.15O2 − δ, Ce0.8Sm0.2O2-δ, La0.88Sr0.12Ga0.82Mg0.18O3 − δ) and protonic (BaCe0.8Sm0.2O3 − δ, Ba2In1.67 W0.33O5 + δ) electrolytes were investigated. The Sr2Ni0.75Mg0.25MoO6 sample was obtained via the combustion method at 1373 K in air. X-ray powder diffraction data and dilatometric measurement show that there is a tetragonal → cubic structure phase transition at 510 K. It was found that the total electrical conductivity of a molybdate ceramic sample strongly depends on the ambient atmosphere and changes from 0.007 S/cm (pO2 = 0.21 atm) to 33.217 S/cm (pO2 = 1 × 10− 19 atm) at 1073 K, respectively. By dilatometry measurement under isothermal conditions it was established that the rapid change in conductivity is most probably connected to the partial reduction of the Mo-ions. TEC values calculated in two temperature ranges of 300-500 K and 500-1073 K were 12.3 × 10− 6 and 13.5 × 10− 6 K− 1, respectively.