The microstructural evolution and grain-boundary influence on electrical properties of Ce0.90Gd0.10O1.95 were studied. The nanoscale powders synthesized from a semibatch reactor exhibited 50% green density and 92% sintering density at 1200degreesC (similar to200degreesC lower than previous studies). Impedance spectra as a function of temperature and grain size were analyzed. The Ce0.90Gd0.10O1.95, with finest grain size possessed highest overall grain-boundary resistance; this contribution was eliminated at temperatures >600degreesC, regardless of grain size. The grain conductivity was independent of grain size and was dependent on temperature with two distinct regimes, indicative of the presence of Gd-Ce'-V-o(oo) complexes that dissociated at a critical temperature of similar to580degreesC. The activation energy for complex dissociation was similar to0.1 eV; the value for the grain-boundary was similar to1.2eV, which was size independent.