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The Synthesis And Properties Of Rare Earth Ions Doped Strontium Tungstate Luminescent Materials

Posted on:2016-12-17Degree:MasterType:Thesis
Country:ChinaCandidate:Y WangFull Text:PDF
GTID:2191330461962716Subject:Organic Chemistry
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Owning to the properties of high brightness, long afterglow, adjustable wavelengh scale and non-radiation substance, more and more attention is paid to the studies of rare earth-doped luminescence materials. They have been widely used in many fields, such as safety indicators, lighting in emergency situations, instruments in automobiles and luminous paint, and so on. Tungstate are considered as ideal hosts for rare earth phosphors owing to their excellent properties, such as abundant raw materials, easy and adaptable synthesis methods, stable crystal structure, ease of the adjustment in their structures and compositions, stable thermal and chemical properties. Versatile luminescent properties can be obtained by doping rare earth ions in tungstate hosts. In addition, the emission position and intensity of the luminescent center in these hosts can be easily tuned. However, the development of the properties has also rendered new requirements on the luminescence materials by further research. Therefore, deep investigations of the processing, perperties, spectra adjusting and controlling of novel tungstate luminescent materials are rather important scientifically and technologically.In this paper, the SrWO4: Dy3+ luminescence materials, SrWO4: Pr3+ luminescence materials, Sr WO4: Eu3+, Dy3+ luminescence materials were prepared by co-precipitation method. Furthermore, their reaction conditions were optimized by means of single factor experiments. The main research work includes the following three aspects.1. SrWO4: Dy3+ luminescent material were successfully prepared via a mild and facile co-precipitation method. The as-prepared samples were further characterized by various analytical techniques. The results showed that the as-prepared samples had a scheelite-type tetragonal structure and spherical microparticles. The excitation spectra show that the Sr WO4: Dy3+ luminescent material can be efficiently excited by ultraviolet and near-ultraviolet light, the optimized Dy3+ concentration is 5% and the calcination temperature is 800℃. Three emission peaks locate at 484(blue), 572(yellow), 661(red)nm under 254 nm excitation, corresponding to transition of Dy3+(4F9/2'6H15/2),(4F9/2'6H(13/2)) and(4F9/2'6H11/2)), respectively. Therefore, it is considered to be a new promising luminescent material for white LED application.2. In this work, a study was undertaken about the structural and photoluminescent properties, at room temperature, of powder samples Sr WO4: Pr3+, synthesized by a co-precipitation method. The as-synthesized Sr WO4: Pr3+ powders were characterized by X-ray powder diffraction(XRD), scanning electron microscopy, energy disperse spectroscopy and photo-luminescence spectroscopy. The results showed that the as-prepared samples had a scheelite-type tetragonal structure and spherical microparticles. The most intense PL emission was obtained at 615nm(3P0'3H6)and 644nm(3P0'3F2) for the sample calcined at 900℃ and the Pr3+ concentration 7%. Furthermore, the temperature-dependent luminescence indicates the Sr WO4: Pr3+ exhibits a small thermal-quenching property. So the Sr WO4: Pr3+ phosphor is able to be applied to UV-LED chip-based red light-emitting diodes.3. SrWO4: Eu3+, Dy3+ luminescent material were successfully prepared by co-precipitation method at room temperature. The as-synthesized Sr WO4: Eu3+, Dy3+ powders were characterized by X-ray powder diffraction(XRD), scanning electron microscopy(SEM), energy disperse spectroscopy( EDS) and photo-luminescence spectroscopy. The results showed that the as-prepared samples had a scheelite-type tetragonal structure and spherical microparticles. The effect of the doping concentration of Dy3+ on the luminescent properties of the obtained products was investigated, and the optimal Dy3+ concentration was experimentally determined to 3%. The optimum ccalcination temperature is 800℃. Furthermore, the emission colors of Sr WO4: Eu3+, Dy3+ can be tuned from near white to yellowish white on co-doping Dy3+ ions, making the Sr WO4: Eu3+, Dy3+ luminescent material a great potential for applications in fluorescent lamps and field emission displays(FEDs). strontium, rare earth ions...
Keywords/Search Tags:Luminescent material, coprecipitation method, tungsten acid
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