Oxidation behaviour of uranium in the internally gelated urania–ceria solid solutions – XRD and XPS studies

Single-phase UO2–CeO2 solid solutions were synthesized through an internal gelation route followed by gel decomposition at 600 °C in Ar laden with moisture and sintering at 1100 °C for 24 h in an atmosphere of Ar + 2% H2. The sintered oxides were oxidized by heating in air at 600 °C for 24 h. The oxidation behaviour of U in the oxidized samples with different Ce contents were investigated using oxygen-to-metal ratio (O/M), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analyses. The oxidized sample with Ce contents less than 70 mol% was found to be a mixture of orthorhombic and cubic phases and that with above 70 mol% Ce was found to be single-phase cubic. The valency of U in the oxidized samples computed from the O/M results was compared with the U 4f7/2 peak positions obtained from XPS.