Understanding the effect of calcium on the properties of ceria prepared by a mixed fuel process

Nanocrystalline (8–12 nm size range) and highly sinter active calcium doped ceria compositions of the general formulae Ce1 − xCaxO2 − δ were prepared by a mixed fuel process. Systematic sintering studies confirmed that the processed powder could be sintered to more than 98% of theoretical density at 1200 °C, a temperature that is much lower than majority of the literature reports on Ce1 − xCaxO2 − δ solid solutions. Owing to the high density, improved ionic conductivity values were obtained for all the compositions. In order to understand the effect of calcium on the properties of undoped ceria, we have correlated the factors like effective index and expected level of oxygen vacancies with the observed ionic conductivity in Ce1 − xCaxO2 − δ solid solutions. A sample containing 20 mol% Ca with a higher effective index (0.9297) and a high level of oxygen vacancy (0.2) exhibited the highest conductivity (1.297 × 10− 2 S/cm) among the Ce1 xCaxO2 − δ compositions investigated, thus highlighting the importance of such factors in controlling the oxide ion conductivity in oxide materials.