Hydrothermal synthesis and properties of Ce1−xLaxO2−δ solid solutions

Abstract

The structure, thermal expansion coefficients, ionic and electronic conductivities of Ce1−xLaxO2−δ (x=0–0.30) solid solutions, prepared for the first time hydrothermally, were investigated. The uniformly small particle size (25–50 nm) of the hydrothermally prepared materials allows sintering of the samples into highly dense ceramic pellets at 1300–1400°C, a significantly lower temperature, compared to that at 1600–1650°C required for ceria solid electrolytes prepared by solid state techniques. The solubility limit of La2O3 in CeO, was determined to be around 20 mol.%. The maximum conductivity, δ600°C ∼6.4×10−3 S/cm with Ea=0.73 eV, was found at x=0.15. The thermal expansion coefficients, determined from high-temperature X-ray data are 11.7±0.6×10−6 K−1 for the CeO2, and, increase with increasing La substitution (15.0×10−6 K−1 at x=0.20).