An XPS investigation of (La₂O₃)_1‐x (CeO₂)_2x (ZrO₂)₂ compounds

Abstract

) 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.

XPS and AES studies of UHTC ZrB2–SiC–Si3N4 treated with solar energy

“…The Zr 3d 5/2 and Zr 3d 3/2 peak positions located at approximately 182.6 and 185.1 ± 0.1 eV are characteristic of the O–Zr bonds in oxide compounds . The Zr atoms are in Zr–O 4 environments (Zr 4+ state).…”

Catalytic oxidation of volatile organic compounds (n-hexane, benzene, toluene, o-xylene) promoted by cobalt catalysts supported on γ-Al2O3-CeO2

“…The full-range XPS spectra of the catalysts are shown in Figure 7. The presence of the Ce3d 5/2 peak at 881.3eV for Co 10 /γ-Al 2 O 3 -CeO 2 and at 887.6 and 904.0eV for Co 20 /γ-Al 2 O 3 -CeO 2 characterize the presence of Ce +3 and Ce +4 in both catalysts (Beche et al, 2008;Beche et al, 2012). The Co2p 3/2 peak at 779.0eV for Co 10 /γ-Al 2 O 3 -CeO 2 and 785.6eV for Co 20 /γ-Al 2 O 3 -CeO 2 characterize the presence of Co 2+ (Lakshmi et al, 2009;Salim and Khawaja, 1992) The surface composition of cobalt is 2.81% for Co 20 /γ-Al 2 O 3 -CeO 2 and 1.35% for Co 10 /γ-Al 2 O 3 -CeO 2 , as expected due to the higher metal content of this catalyst.…”

Experimental and first-principles DFT study on oxygen vacancies on cerium dioxide and its effect on enhanced photocatalytic hydrogen production

“…Figure 6 shows the XPS spectra for Ce 3d of CeO 2 (400 o C). Among all of these ten peaks, v, v'', v''', u, u'' and u''' are attributed to the present of Ce (IV), and v 0 , v', u 0 and u', however, are attributed to the present of Ce (III) [27]. The amounts of Ce (III) and Ce (IV) were calculated from the components of the Ce 3d core level using the following equations [27,28]:…”