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RELATION ENTRE FONCTION DIÉLECTRIQUE ET PROPRIÉTÉS OPTIQUES : APPLICATION À LA RECHERCHE D'ABSORBEURS UV INORGANIQUES DE DEUXIÈME GÉNÉRATION

Abstract : The thesis deals with the synthesis and the characterization of second generation inorganic UV absorbers. The analysis of the optical properties is carried out by means of electron energy loss spectroscopy (EELS) measurements and the calculation of the dielectric function by DFT methods. Our study concerns cerium III borates, cerium IV oxides, titanium oxiphosphates, silicates and oxisilicates, and A3PMo(12-x)WxO40 (A = Na, K, Rb) solid solutions. The study of borates shows that the Ce_4f -5d transition turns out to be much less intense than the anion-cation charge transfer. Thus, the f to d electronic transition appears inappropriate in the quest of high absorbing materials. For the other compounds, the role of the coordination of elements implied in the absorption process and of the covalence of the oxygen-metal (lanthanide) bond on the absorption threshold position, the intensity of the transition (and consequently on the refractive index) has been evidenced by the quantitative and qualitative analysis of the oxygen-metal (or lanthanide) charge transfer. Moreover, K3PMo12O40, material containing discrete anion of Keggin type, exhibits optical properties (Lab coefficients) similar to commercialized yellow pigments. Using molybdenum-tungsten solid solution gives the possibility to vary the absorption threshold between 2.5 and 3.2 eV, and to decrease the compounds reducibility.
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Contributor : Fabrice Goubin <>
Submitted on : Friday, November 14, 2003 - 11:43:21 AM
Last modification on : Thursday, March 5, 2020 - 3:23:26 PM
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Fabrice Goubin. RELATION ENTRE FONCTION DIÉLECTRIQUE ET PROPRIÉTÉS OPTIQUES : APPLICATION À LA RECHERCHE D'ABSORBEURS UV INORGANIQUES DE DEUXIÈME GÉNÉRATION. Matériaux. Université de Nantes, 2003. Français. ⟨tel-00003749⟩

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