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Photophysical and morphological study of the tungstates of alkaline earth metals doped with rare earth prepared by hydrothermal method utilizing microwave


Luminescent properties of alkaline earth metals tungstates have been extensively investigated in various industrial applications such as optical fiber, humidity sensor, catalysts, flash detector, solid state lasers, fotocatalysts photoluminescent displays, etc.. Tungstate minerals present scheelite structure, as well as good characteristics, which could provide excellent conditions to become an optically active material. Its synthesis has been carried out by conventional methods such as solid state reaction, sputtering, Czochralski Method, etc.. The microwave hydrothermal method is a process quite attractive to synthesize diverse materials, since the reactions occur in shorter times when compared to those obtained using conventional ones. Rare earth trivalent ions are intensively studied by photoluminescent spectroscopy. Among these the Eu3+ has been the most investigated as a result of the simplicity of its emission spectrum and due to its wide application as red phosphorus for color TV screens. This ion has also attracted significant attention of researchers because of its potential application as biological sensors, electroluminescent devices, phosphors, lasers or optical amplifiers when doping a variety of materials. In addition, the Eu3+ luminescence spectra present emission bands that extend from visible to infrared region, since it possess an energy levels structure relatively simple. Especially the transitions 5D0 ’ 7FJ (J = 0, 1, 2, ...6), allows the exploration of the Eu3+ surrounding through this technique, making the Eu3+ an ideal experimental probe of the tungstate matrix. The ion Tb3+ has also been studied due to its optical properties, promising inorganic materials being used due to its characteristic green emission related to the strong 5D4 ’ 7F5 transition, whose emission band appears in the region of 520 nm of its photoluminescent spectrum. In this project pure and SrWO4 powders doped with rare earths are synthesized by co-precipitation method and hydrothermally processed in a microwave oven using 140 oC for different times of heat treatment. We intend to start our studies using Eu3+ after all we will study Tb3+ as doping. The obtained powders will be analyzed by x-ray diffraction (XRD), Raman Spectroscopy and scanning electron microscopy (FEG-SEM). The studies of the photoluminescent properties of these powders will be performed through the analyses of excitation and emission spectra of rare earth ions used, as well as the lifetime of the lifetime of the pure matrix. (AU)

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