TEM and XPS analysis of CaxCe1-xO2-y (x = 0.05–0.5) as electrolyte materials for solid oxide fuel cells

The microstructure and conductivity property of Ca-doped CeO2 were studied in a wide range of dopant concentrations (from 5 to 50 at.%). Through detailed transmission electron microscopy and X-ray photoelectron spectroscopy investigations, we determined the secondary phase besides the doped ceria, clarified the solubility limit for the dopant and specified the reduction behavior of CeO2 induced by the Ca doping and the associated reduction product. The influences of the microstructures on the ionic conductivity of Ca-doped CeO2 are discussed, from which the optimal doping level of Ca is suggested.