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.
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