Synthesis and characterization of co-doped ceria ceramics by sol-gel method

Abstract

Doped and co-doped ceria electrolyte materials are very useful in solid oxide fuel cells. The Ce0.9Sm1−xSrxO2 (x = 0–0.09) compositions were synthesized through the sol-gel method. Dense Ce0.9Sm1−xSrxO2 ceramics were obtained through sintering the pellets at 1300°C for 8 h. XRD measurements indicate that all synthesized materials crystallized in cubic fluorite-type structure. Average crystallite size of the samples was in the range 21–27 nm. The relative density of Ce0.9Sm1−xSrxO2 samples was over 94% of the theoretical density. The lattice parameter increased linearly with increasing Sr concentration in Ce0.9Sm1−xSrxO2 following Vegard's rule. Surface morphology was analyzed using SEM. It was observed that the thermal expansion increased linearly with increasing temperature. The two-probe a.c. impedance spectroscopy was used to study the grain, grain boundary and total ionic conductivity of doped and co-doped ceria in the temperature range 250°–500°C. The Ce0.9Sm0.07Sr0.03O2 composition showed higher grain ionic conductivity and minimum activation energy at 500°C. © 2011, Copyright The Indian Ceramic Society.