This article presents an XPS study of Ce 3d emission spectra dominated by atomic multiplet effects in core level spectroscopy of rare earth compounds (Ce oxides). Core level spectroscopy has been used to study the electronic states of Ce 3d 5/2 and Ce 3d 3/2 levels in Ce 4+ and Ce 3+ states. The well-resolved components of Ce 3d 5/2 and Ce 3d 3/2 spin-orbit components, due to various final states (4f 0 , 4f 1 , 4f 2 configurations), were determined on 3d XPS spectra from commercial powders (CeO 2 , CePO 4 ).These results were used to study the 3d spin-orbit component of mixed cerium-titanium oxide. This compound was prepared by co-melting commercial powders of CeO 2 and TiO 2 at 1800 K under air using a solar furnace with a flux density of 16 MW.m −2 at the focal point of the parabolic concentrator. The mixed oxide Ce 2 Ti 2 O 7 was produced and contained Ce(III) species which may be reactive with water to give back the initial metal oxides and generate hydrogen, a valuable product considered as a promising energy carrier in the future in replacement of oil.The 3d photoemission spectra revealed the presence of mixed components attributed to mainly Ce(III) and Ce(IV) species.

) 1-x (CeO 2 ) 2x (ZrO 2 ) 2 mixed oxides (LCZ) where 0 ≤ x ≤ 1 were synthesised from commercial La 2 O 3 , CeO 2 and ZrO 2 powders and co-melted in a 2-kW solar furnace. These samples were re-oxidised in air at temperatures that ranged from 900 K to 1100 K. The microstructures of the LC, LCZ and CZ oxides were investigated by XPS and XRD. Core-level spectroscopy (XPS) has been used to study electronic states (III) and (IV) of the Ce 3 d 5/2 and Ce 3 d 3/2 levels. The resolved components of the Ce 3 d 3/2 , 5/2 features were identified. The rate of Ce 3+ and Ce 4+ states were calculated for different values of x (0.1-1). The nature of the chemical bonds of Ce and O were determined from the Ce 3 d 3/2,5/2 and O 1 s photoelectron peaks, respectively.The XRD study revealed the presence of solid solutions (LCZ and CZ). The presence of crystalline phases (pyrochlore and fluoritelike structures) depends on the value of x. A decrease in the lattice parameter was observed with increasing x. La atoms were substituted by Ce atoms in a solid solution, and the oxygen vacancies were filled. The amount of fluorite-like phase increases with an increasing amount of Ce atoms.

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