Electrical properties optimization of calcium Co-doping system: CeO ₂-Sm ₂O ₃

In order to optimize the electrical properties of co-doped ceria electrolytes, Ce _0.8Ca _0.15Sm _0.05O _2-δ (CCS) sintered at different temperatures (1150 °C, 1200 °C, 1250 °C, 1300 °C and 1350 °C for 8 h) have been prepared and systematically investigated. It is found that among these samples sintered at different conditions, the electrical conductivity (σ) measured at 800 °C can be ranked as: CCS _{1250 °C}: σCCS _1250°C800°C = 2.38 × 10 ^-2 S cm ^-1 > CCS _{1200 °C}: σCCS _1200°C800°C = 1.81 × 10 ^-2 S cm ^-1 > CCS _{1150 °C}: σCCS _1150°C800°C = 1.50 × 10 ^-2 S cm ^-1 > CCS _{1300 °C}: σCCS _1300°C800°C = 1.26 × 10 ^-2 S cm ^-1 > CCS _{1350 °C}: σCCS _1350°C800°C = 0.68 × 10 ^-2 S cm ^-1. The electrical conductivity of CCS increases with the increase of sintering temperatures, and the 1250 °C-sintered sample presents the highest conductivity because of the best microstructures. However, the electrical conductivity of CCS decreases when the sintering temperatures goes beyond 1250 °C. We attribute this to the phase instability. It reveals that microstructures and the phase stability have important effects on the optimization of electrical properties for the co-doped ceria electrolytes.