An XPS investigation of (La ₂ O ₃ ) _{1‐ <i>x</i>} (CeO ₂ ) _{2 <i>x</i>} (ZrO ₂ ) ₂ compounds

Abstract

(La 2 O 3 ) 1‐ x (CeO 2 ) 2 x (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 fluorite‐like 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. Copyright © 2012 John Wiley &amp; Sons, Ltd.