The acetylacetone precursor method was used to obtain powders of various ceria-based compositions, Ce0.8Ln0.2O2−δ. The powders were used to prepare disks which were sintered at 1150C after adding Co nitrate, or at 1500C without Co. The materials were characterized by using impedance spectroscopy to distinguish the bulk and grain-boundary behaviors. Arrhenius plots of bulk conductivity data revealed a gradual change in slope; indicating defect interactions upon cooling to intermediate, and relatively low, temperatures. The data for various doped-ceria samples converged in the high-temperature range, but significant differences in conductivity and activation energy were found at low temperatures. The grain-boundary behavior exhibited a dependence upon the trivalent additive (Y, La, Gd, Sm) and the highest grain-boundary conductivity, for samples obtained without adding cobalt nitrate, was found for samples with La. The addition of cobalt nitrate, and sintering at relatively low temperature, enhanced the grain boundary conductivity of the remaining materials. The highest specific grain-boundary conductivity was then found for samples containing Sm. Differences in the grain-boundary behavior were interpreted on the basis of differences in segregation of the rare-earth additives for samples without Co-doping and of the preferential segregation of Co in Co-doped samples.

Grain Boundary Conductivity of Ce0.8Ln0.2O2−δ Ceramics (Ln = Y, La, Gd, Sm) with and without Co-Doping. D.Pérez-Coll, D.Marrero-López, P.Núñez, S.Piñol, J.R.Frade: Electrochimica Acta, 2006, 51[28], 6463-9