Composites of equiatomic Y, La, Ce, Nd, and Gd rare earth oxides: Chemical-shift effects and valence spectra
Jungsu Bin, Hyunbae Gee, Taesung Park, UiJun Go, Jeoung Han Kim, Youn-Seoung Lee
Abstract
The core-electron and valence spectra of the composites of equiatomic rare earth oxides (equi-REO) were investigated using XPS . Equi-REOs fabricated by annealing at 1600 °C for 10 h after the synthesis by mechanical ball-milling and chemical sol-gel methods, exhibited the FCC bixbyite single phase. It was confirmed that Y and La sites had the higher oxidation state (Y > 3+ and La >3+ ) than Y 2 O 3 (Y 3+ ) and La 2 O 3 (La 3+ ), respectively, and both Gd and Nd sites had the lower oxidation state (Gd < 3+ and Nd <3+ ) than Gd 2 O 3 (Gd 3+ ) and Nd 2 O 3 (Nd 3+ ), one the other hand, in the Ce site, Ce 3+ was increased compared to CeO 2 , and Ce 3+ and Ce 4+ were mixed. There were a significant changes in the electron DOS associated with O 2p – 4f hybridizations in the equi-REOs compared to the ideal mixture. Finally, we found that the chemical sol-gel process induces more changes of chemical and electronic states of the equi-REO than the mechanical ball milling process.