XPS investigations on cesium uranates: mixed valency behaviour of uranium

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Several pure cesium uranate phases were prepared (Cs 2U 2O 7, Cs 2U 4O 13, Cs 2U 4O 12, Cs 4U 5O 17) and measured with X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Detailed XPS scans of the main photoelectron peaks (U 4f, Cs 3d, O 1s and valence band) were made. Peak positions, peak widths and satellite positions were measured and compared between the uranates. A systematic shift in the position of the U 4f lines was found to be correlated with the Cs/U ratio. The mixed valency behaviour of uranium was observed and studied. Interpretation of the satellite structure of the U 4f peaks and the deconvolution of these peaks have been used to quantify the chemical states of uranium present in the mixed valency compound Cs 2U 4O 12.