XPS STUDIES ON CERIUM, ZIRCONIUM AND YTTRIUM VALENCE STATES IN PLASMA-SPRAYED COATINGS

XPS is used for investigating the valence state of the chemical elements present in 25.5 wt% CeO2-2.5 Y2O3-72 ZrO2 plasma sprayed coatings as a function of the deposition temperature. The analysis of Ce 3d binding energy and satellite structures shows that CeO2 after spraying is either partially reduced to Ce (III) at low deposition temperature, or remains essentially unchanged at high deposition temperature. In both cases, the presence of Zr=2-x suboxides is found, which does not depend apparently on the cooling rate