XPS spectra of the U5+ compounds KUO3, NaUO3 and Ba2U2O7

Valence states of uranium in three ternary uranates KUO3, NaUO3 and Ba2U2O7 were studied using X-ray photoelectron spectroscopy (XPS). The analysis of the U4f photoelectron peak positions, peak widths at half maximum and satellite positions of U4f peaks, shows that the uranium in these compounds is present in a single valence state, namely U5+. Since the surface of these compounds is extremely susceptible to oxidation, the XPS spectra were measured after a carefully controlled etching of the surface using an Arþ ion beam so that the surface oxidation does not affect the XPS studies.