Elaboration et caracterisation structurale et optique de matrices dielectriques dopees par des nanomateriaux

Abstract

This work focused on the development and characterization of single crystals of KCl and KBr pure and doped by the particles of SrCl2 (H2O). The prepared nanocompositesKBr /KSr2Br5 andKCl / KSr2Cl5 were the subject of a structural and optical characterization by various methods suited to the study of the properties of nanomaterials. Simples (single crystals) of the materials prepared using the Czochralski method have cylindrical morphology with a diameter of 08 to 20mm and up to 80mm length. Several complementary techniques were used to structurally and optically characterize the elaborated materials to highlight their structural features and their optical properties. The characterization by X-ray diffraction showed: - That pure matrices of KCl and KBr have cubic single crystal structure and have orientation along the crystallographic axis [100]. - That the doped matrices kept their appearance despite the incorporation of nanoparticles after doping. - That during the preparation of the samples which occurs at high temperature, the doping particles have chemically reacted with the host matrix and permit the in situ synthesis of the particles of KSr2Cl5andKSr2Br5. - That the crystallites size of KSr2Cl5 and KSr2Br5 are nanoscale order - That the quality of the synthesized crystallites KSr2Cl5 and KSr2Br5 is good sight of the importance of the intensity of the diffraction peaks The characterization by Raman and IR spectroscopy has not given clear informations as there is little prior scientific work on the vibration modes of the elaborated compounds to compare and confirm our results. - There is an absence of Raman peaks, which means that the crystallites KSr2Cl5 and KSr2Br5 located deep (within the matrix), the emitted radiation can be absorbed (decreased) by the matrix and not detected Characterization by measuring the optical absorption revealed: - The pure KCl and KBr host matrices are transparent in the near infrared - visible - near ultraviolet. - That the prepared nanocompositesKCl / KSr2Cl5 and KBr / KSr2Br5 have absorption bands in the visible range. - That the optical gap of the prepared nanocomposites is lower than in pure KCl and KBr matrices. Characterization by radioluminescence at room temperature showed: -that prepared nanocompositesKCl / KSr2Cl5 and KBr / KSr2Br5 exhibit luminescence in the visible range. This characteristic makes these materials candidates which might come in the manufacture of components for optical systems using shorter wavelengths