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Caractérisations structurales et optiques d'ultraphosphates de terres rares LnP5O14 (Ln=La, Gd et Y) synthétisés par la voie solide et par le procédé sol-gel

Abstract : This work deals with the development of polycrystalline Eu and/or Tb activated ultraphosphate luminophors of formula LnP5O14 (Ln = Gd, La,Y) synthesized by the sol-gel process. The experimental conditions have been optimized. The characterization of the intermediate and final materials has been carried out from the structural point of view using DRX, IR and Raman, NMR techniques and from the morphological point of view using both SEM and Laser granulometry. The use of Eu3+ as fluorescent probe allowed specifying the materials characterization by identifying the spectral signature of the emitting centers in relationships with their crystallographic environment. Both monoclinic C2/c and orthorhombic Pnma polymorphs of YP5O14 have been characterized using single-crystal XRD. An extended crystal chemical study of LnP5O14 ultraphosphate revealed the existence of a monoclinic C2/c form for both Eu and Gd members and invalidated the existence of the orthorhombic Pmna form of rare earths of greatest ionic radii. This apparent polymorph should be better described in the monoclinic P21/c symmetry. The study of the luminescence properties under VUV excitation of Eu3+ doped ultraphosphates showed that the requirement for using these matrices as plasma display panels are achieved. In the Gd matrix a process of down-conversion may induce an energy transfer between Gd3+ and Eu3+ ions when the excitation reaches the characteristic absorption band of the ultraphosphate matrix.
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Submitted on : Monday, August 27, 2012 - 2:07:01 PM
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  • HAL Id : tel-00725579, version 1

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Aïcha Mbarek. Caractérisations structurales et optiques d'ultraphosphates de terres rares LnP5O14 (Ln=La, Gd et Y) synthétisés par la voie solide et par le procédé sol-gel. Matériaux. Université Blaise Pascal - Clermont-Ferrand II, 2009. Français. ⟨NNT : 2009CLF21928⟩. ⟨tel-00725579⟩

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