Electrical properties optimization of calcium Co-doping system: CeO2–Sm2O3

In order to optimize the electrical properties of co-doped ceria electrolytes, Ce0.8Ca0.15Sm0.05O2−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: CCS1250 °C: σ CCS 1250 ° C 800 ° C  = 2.38 × 10−2 S cm−1 > CCS1200 °C: σ CCS 1200 ° C 800 ° C  = 1.81 × 10−2 S cm−1 > CCS1150 °C: σ CCS 1150 ° C 800 ° C  = 1.50 × 10−2 S cm−1 > CCS1300 °C: σ CCS 1300 ° C 800 ° C  = 1.26 × 10−2 S cm−1 > CCS1350 °C: σ CCS 1350 ° C 800 ° 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.