Study of gadolinia-doped ceria solid electrolyte surface by XPS

Gadolinia-doped ceria (CGO) is an important material to be used as electrolyte for solid oxide fuel cell for intermediate temperature operation. Ceria doped with 10 mol% gadolinia (Ce0.9Gd0.1O1.95) was prepared by conventional solid state synthesis and found to be single phase by room temperature X-ray diffraction (XRD). The chemical states of the surface of the prepared sample were analyzed by X-ray photoelectron spectroscopy (XPS). Though Gd was present in its characteristic chemical state, Ce was found in both Ce4+ and Ce3+ states. Presence of Ce3+ state was ascribed to the differential yield of oxygen atoms in the sputtering process.