AN XPS, ISS AND ESR COMPARATIVE-STUDY OF 8-COORDINATION OF COPPER(II) IONS IN THE CUTHO COMPOUNDS

In this study, we attempted to clarify the coordination state and the distribution of copper (II) ions in the CuThO compounds prepared by coprecipitation, by using several physico-chemical techniques in particular, X-Ray Photoelectron Spectroscopy (XPS). For atomic ratios Cu/Th < 0.25, the copper (II) species are mainly located near the thoria surface. The Cu2p3/2 level shows a chemical shift towards the lower binding energy compared to Cu2+ ions in CuO and also a net decrease in the intensity of the satellite peak, characteristic of copper (II). A relation between these observations and the covalent character of Cu2+-O2- bond is established. Eightfold coordination of copper (II) in the thoria lattice is evident. These conclusions are in good agreement with Electron Spin Resonance (ESR) results. For a higher atomic ratio (Cu/Th > 0.25), a formation of copper oxide crystallites is observed on the thoria surface.