Processing and characterization of CoO and Sm2O3 codoped ceria solid solution electrolyte

Abstract

A series of ceria-based solid solution electrolytes, CoO and Sm2O3 codoped ceria Ce0.8Sm0.2−xCoxO2−δ (denoted as CSO for x=0 and CSCx for x=0.01–0.09), are synthesized via a carbonate co-precipitate method. The phase composition of the precursor is determined by XRD, EA and TG/DSC. The oxidation valence of Co in the samples calcined at different temperatures is probed by XPS and determined to be in +2 valence state at the temperature >1000°C. The sintering investigation demonstrates that the addition of Co promotes densification to occur at lower temperatures with a uniform grain growth. Impedance spectroscopy measurements indicate an improvement in the grain and the grain boundary conductivities for the samples with appropriate Co/Sm ratio. The optimal amount of Co additive is proved to be 7mol%. It shows that CSC0.07 exhibits higher conductivity (σt=0.0538Scm−1 at 600°C) and lower activation energy (Ea=0.567eV) compared with CSO and other CSCx. The results suggest that cobalt oxide could be used not only as an effective sintering aid but as a favorable dopant to ceria as well.