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Binding effects in sulfur Kα and Kβ x-ray emission spectra
摘要： A systematic study has been carried out in order to investigate the influence of the chemical bond in the occurrence of the different sulfur decays to 1s vacancy states induced by electron impact. A number of samples in different oxidation states (+4, +6, 0 and ?2) were irradiated in a commercial microscope, acquiring Kα and Kβ spectra for all sulfur oxidation states. Special attention has been paid to the case of emissions associated to decays corresponding to multiple ionizations. An important achievement of the present study is the high resolution obtained in the wavelength-dispersive spectra acquired with a commercial spectrometer.
关键词： electron impact,chemical bond,wavelength-dispersive spectra,oxidation states,sulfur,Kα and Kβ spectra
更新于2025-09-10 09:29:36
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First-Principles Insights into the Oxidation States and Electronic Structures of Ceria-Based Binary, Ternary and Quaternary Oxides
摘要： Ceria and ceria-based materials have versatile technological and industrial applications, physically ascribed to the flexible fluctuation of Ce oxidation state between Ce4+ and Ce3+. A considerable multi-disciplinary research has been spent to obtain Ce oxidation state, the crucial quantity regarding the application; however, a rigorous and physically correct determination of oxidation state is still lacking. Here we conduct first-principles DFT + U calculations to unambiguously determine the physical oxidation state of Ce in ceria-based materials such as the homogenous CenO2n-2 (n = 7, 9, 10, 11, 12), ceria doped by multivalent Ti and V, Ce-Ti(V)-O ternary compounds, and Ce-Ti-V-O quaternary compounds. The results show that Ce oxidation state depends on the local structure and chemical surrounding: Oxygen vacancy facilitates the transition from Ce4+ to Ce3+, consistent with the localization of Ce 4f electrons; Ti and V with the 3d energy levels higher than 4f energy levels of Ce generally tend to reduce Ce4+ to Ce3+ particularly under the oxygen-deficiency condition. The atom-resolved determination of Ce oxidation states in the complicated compounds offers great promise for understanding the physical and chemical behavior of ceria-based materials, and for rational design of novel ceria-based materials for application potentials.
关键词： Ceria-based materials,First-principles calculations,Electronic structures,DFT + U,Oxidation states
更新于2025-09-04 15:30:14