Preparation and properties of dense Ce0.9Gd0.1O2−δ ceramics for use as electrolytes in IT-SOFCs

Gd-doped ceria solid solutions have been recognized to be leading electrolytes for use in intermediate-temperature fuel cells. In this communication, it reported on the preparation, solubility and densification of Ce0.9Gd0.1O2−δ ceramics derived from carbonate coprecipitation. The dissolution of Gd2O3 in CeO2 lattice was identified to complete during coprecipitation process by studying lattice parameter against temperature. The calcining temperature was found to have a significant influence on the densification behavior and final sintered density for the carbonate-coprecipitated powder. The samples prepared from the powder calcined at ≤700 °C had an expansion at ∼1250 to 1400 °C during sintering, and thus lowered sintered density. 800 °C was identified to be an optimal calcining temperature for carbonate-coprecipitated powder. The powder calcined at 800 °C for 2 h had a mean crystalline size of ∼25 nm with nearly spherical shape and narrow particle-size distribution, which had a maximum densification rate at ∼1190 °C. This temperature (of maximum densification rate) could further be reduced to ∼1080 °C for the carbonate-coprecipitated powder by adding 0.5 at.% FeO1.5 (atomic ratio). At 1200 °C for 5 h, over 98% relative density with an average grain size of ∼1.2 μm was obtained for the 0.5 at.% Fe-loaded Ce0.9Gd0.1O2−δ ceramics. Fe loading was also found to have a positive effect on grain boundary conductivity of Ce0.9Gd0.1O2−δ ceramics. An increase in the grain boundary conduction by over two times was achieved in the present work for the 0.5 at.% Fe-loaded Ce0.9Gd0.1O2−δ ceramics.