Hydrothermal synthesis and properties of Ce1−xEuxO2−δ solid solutions

The structure, thermal expansion coefficients and ionic and electronic conductivities of Ce1−xEuxO2−δ (x=0–0.50) solid solutions, prepared hydrothermally for the first time, were investigated. The uniformly small particle size (40–55 nm) of the hydrothermally prepared materials allows sintering of the samples into highly dense ceramic pellets at 1300–1400°C, a significantly lower temperature than 1600–1650°C, which is required for samples prepared by solid-state techniques. X-ray absorption spectroscopy (XAS) was used to establish the pure Eu3+ character of the europium ions; XAS also reflects local disorder effects. The highest conductivity was found for Ce0.85Eu0.15O1.925−δ (σ700°C=2.6×10−2 S/cm, Ea=0.66 eV) with predominantly oxide-ion mobility.