Preparation And Fluorescence Properties Of Luminescent Materials For WLED

White light emitting diodes （WLED） as a fourth-generation solid-statelighting source has a lot of advantages, especially as fluorescent conversionWLED, which is the focus of the present study. Luminescent materials play animportant role in developing WLED, the preparation and application of whichattract much attention.In this paper, the stannate red luminescent materials by precipitation-hydrothermal, the halogen phosphate green luminescent materials by sol-geltechnique followed with microwave heating, and the silicate blue luminescentmaterials by combustion method. The luminescent materials were characterizedby X-ray diffraction, TG/DTA, scanning electron microscopy, infraredspectroscopy, Raman spectroscopy and fluorescence spectrum. The influences ofpreparation method, reacion conditions, sintering system and doping ions on thecrystal structure, reaction degree, surface morphology and fluorescenceproperties of luminescent materials were discussed.The stannate red luminescent materials La_0.01Y_1.99Sn2_O7:Eu³⁺,Dy³⁺weresuccessfuly synthesized by the precipitation-hydrothermal method. The resultsshow that the structure and morphology were influencecd by the hydrothermalconditions such as filling degree, pH value, temperature and reaction time, aswell as sintering temperature and time. The mechanism in synthesizingluminescent materials by precipitation-hydrothermal method was discussed. Thestannate red luminescent materials with optimal luminescent properties wereobtained at the Eu doping amount of0.0005and the Eu: Dy mole ratio of1:3.The precursor of halogen phosphate green luminescent materialsSr₅（PO₄）₃Cl:Tb³⁺,Tm³⁺were synthesized by the sol-gel method, followed bymicrowave heating sintering. The factors, such as pH value, the amount ofcomplexing agents and the solution concentration during precursor preparation, were investigated, and their influences on the crytal structure, grain size andsurface morphology of luminescent materials were duscussed. The comparativestudies were carried out between high-temperature sintering and microwavesintering to investigate the influences of different sintering methods on thestructure of the materials, thus obtaining the optimal sintering temperature,heating power and microwave treating time. When the mole ratio of Sr and Tb is100:2and the mole ratio of Tb and Tm is1:2, the fluorescence intensity of theluminescent material is strong.The silicate blue luminescent materials Ba_xCa_1-xSiO₄:Eu²⁺,Gd³⁺wereprepared by combustion method. The optimal parameters were obtained,including the mole ratio of burning agent, furnace temperature, second sinteringtemperature and holding time. When the mole ratio of metal ions and Eu is100:3and the mole ratio of Eu: Gd is1:1.5, the fluorescence intensity is preferabe. Thesurface morphology and luminescence intensity of the luminescent materialschanged with Ba/Ca ratio. Based on three kinds of luminescent materials asprepared, white light was obtained according to the c olor coordinate. Thus, theluminescent materials can be applied in developing WLED.