Hydrothermal synthesis and properties of mixed conducting Ce1-xTbxO2-δ solid solutions

The structure, thermal expansion coefficients, and ionic and electronic conductivities of Ce1-xTbxO2-delta (x = 0-0.30) solid solutions, prepared hydrothermally for the first time, were investigated. The uniformly small particle size (33-40 nm) of the hydrothermally prepared materials allows sintering of the samples into highly dense ceramic pellets at 1300-1400 degrees C, a significantly lower temperature, compared to that at 1600-1650 degrees C required for samples prepared by solid-state techniques. X-ray absorption near edge spectroscopy was used for the identification of Tb3+/Tb4+ ions. The maximum of total conductivity was found at x = 0.25 (sigma(700 degrees C) = 2.1 X 10(-2) S/cm, E-a = 0.49 eV) with electronic contribution to the total conductivity around similar to 50% at 600-700 degrees C. The conductivity becomes more ionic with decreasing Tb substitution. The thermal expansion coefficients, determined from high-temperature X-ray diffraction data, are 11.7 x 10(-6) K-1 for CeO2 and slowly decrease with increasing Tb substitution (10.8 x 10(-6) K-1 at x = 0.30).