LOCAL ELECTRONIC STRUCTURE OF CE-DOPED Y2O3 : AN XPS AND XAS STUDY

An experimental study of the local electronic structure of Ce-doped yttria (2% and 5% at.) was performed using photoelectron and x-ray-absorption spectroscopies (XPS and XAS). The local atomic arrangement in the solid solutions is well represented by an eightfold oxygen coordination around Ce atoms, with a Ce-O distance shorter than in ${\mathrm{CeO}}_{2}$ (2.28 \AA{} as Y-O instead of 2.34 \AA{}). The x-ray-absorption spectra measured at the Ce ${\mathit{L}}_{3}$ edge and the Ce 3d photoelectron lines are characteristic of the ${\mathrm{CeO}}_{8}$ environment, as in ${\mathrm{CeO}}_{2}$. However, the changes observed in the excitation spectra of the solid solutions are characteristic of an increase of the charge-transfer energy, due to the shortening of the Ce-O distance. The oxygen K-edge spectra evidence the existence of extended unoccupied f-character states, characteristic of tetravalent Ce.