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Open Access item The behavior of mixed-metal oxides: Physical and chemical properties of bulk Ce1–xTbxO2 and nanoparticles of Ce1–xTbxOy

Authors:Wang, Xianqin
Hanson, Jonathan C.
Liu, Gang
Rodríguez, José A.
Iglesias Juez, Ana
Fernández García, Marcos
Keywords:Nanoparticles, Crystal defects, Vacancies (crystal), Raman spectra, XANES, X-ray diffraction, Density functional theory
Issue Date:15-Sep-2004
Publisher:American Institute of Physics
Citation:Journal of Chemical Physics 121(11): 5434 (2004)
Abstract:The physical and chemical properties of bulk Ce1–xTbxO2 and Ce1–xTbxOy nanoparticles (x<0.5) were investigated using synchrotron-based x-ray diffraction (XRD), x-ray adsorption near edge spectroscopy (XANES), Raman spectroscopy (RS), and first-principles density-functional (DF) calculations. DF results and Raman spectra point to a small tetragonal distortion after introducing terbium in ceria. The results of XRD show a small contraction ( <0.08 Å) in the cell dimensions. The presence of Tb generates strain in the lattice through the variation of the ionic radii and creation of crystal imperfections and O vacancies. The strain increases with the content of Tb and affects the chemical reactivity of the Ce1–xTbxOy nanoparticles towards hydrogen, SO2, and NO2. DF calculations for bulk Ce1–xTbxO2 and Ce8–nTbnO16 (n = 0, 1, 2, or 4) clusters show oxide systems that are not fully ionic. The theoretical results and XANES spectra indicate that neither a CeTb exchange nor the introduction of oxygen vacancies in Ce1–xTbxOy significantly affect the charge on the Ce cations. In contrast, the O K-edge and Tb LIII-edge XANES spectra for Ce1–xTbxOy nanoparticles show substantial changes with respect to the corresponding spectra of Ce and Tb single oxide references. The Ce0.5Tb0.5Oy compounds exhibit a much larger Tb3+/Tb4+ ratio than TbO1.7. A comparison with the properties of Ce1–xZrxOy and Ce1–xCaxOy shows important differences in the charge distribution, the magnitude of the dopant induced strain in the oxide lattice, and a superior behavior in the case of the Ce1–xTbxOy systems. The Tb-containing oxides combine stability at high temperature against phase segregation and a reasonable concentration of O vacancies, making them attractive for chemical and catalytic applications.
Description:11 pages, 12 figures, 3 tables.-- PACS: 61.46.+w; 61.72.Ji; 78.70.Dm; 78.30.Hv; 71.15.Mb; 64.75.+g; 82.65.+r
Publisher version (URL):http://dx.doi.org/10.1063/1.1781116
Appears in Collections:(ICP) Artículos

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