Ceria-carbonate composite for low temperature solid oxide fuel cell: Sintering aid and composite effect

•Ceria-carbonate composites with various carbonate contents.•Sintering aids at low carbonate contents, 400 °C less than the carbonate-free sample.•Composite effect in the large carbonate content (>10%).•SDC-20 wt% LiNaCO3 presented the optimal properties.

In this study, the effect of carbonate content on microstructure, relative density, ionic conductivity and fuel cell performance of Ce0.8Sm0.2O1.9-(Li/Na)2CO3 (SDC-carbonate, abbr. SCC) composites is systematically investigated. With the addition of carbonate, the nano-particles of ceria are well preserved after heat-treatment. The relative densities of SCC pellets increase as the carbonate content increases or sintering temperature rises. Especially, the relative density of SCC2 sintered at 900 °C is higher than that of pure SDC sintered at 1350 °C. Both the AC conductivity and DC oxygen ionic conductivity are visibly improved compared with the single phase SDC electrolyte. Among the composites, SDC-20 wt% (Li/Na)2CO3 (SCC20) presents high dispersion, relative small particle size, and the dense microstructure. The optimized microstructure brings the best ionic conductivity and fuel cell performance. It is hoped that the results can contribute the understanding of the role of carbonate in the composite materials and highlight their prospective application.