An XPS, ISS and ESR Comparative Study of Eight-Coordination of Copper (II) Ions in the CuTho Compounds

Abstract

Abstract 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 (11). A relation between these observations and the covalent character o f Cuzt- 02- bond i s esta- blished. Eightfold coordination of copper (11) i n the thoria lattice i s evident. These conclusions are in good agreement with Electron Spin Resonance (ESR) results. For a higher atomic ratio (Cu/Th > 0.25), a formation o f copper oxide crystallites i s observed on the thoria surface.