Prearation And Properties Of Rare Earth Doped Tungstates Salt-sype Light-emitting Materials

As a transition metal salt, tungstate is a kind of important phosphormaterial. It is used as a scintillator material, fiber optic and magneticdevices, etc. The preparation methods of tungstate luminescentmaterials reported are high temperature solid phase synthesis, sol gelmethod, citric acid complex method and hydrothermal method, etc.Tungstate luminescence materials have been prepared byco-precipitation method. Because the process is simple and theoperation is convenient. The optimum process conditions can be findout by more experiments.This paper outlines the composition, preparation methods,development of solid luminescent materials and light-emittingmechanism of luminescent materials. MWO34:Eu+, MWO4:Tb3+(M=Ca,Sr), MWO3+4:Eu,Tb3+(M=Ca, Sr) luminescent materials were preparedby co-precipitation method. By using fluorescence spectroscopy, X-raydiffraction (XRD), and scanning electron microscopy (SEM) on theluminescent properties, material structure and the morphology wereanalyzed.The result shows that the material prepared is MWO4(M=Ca, Sr)crystals which have a tetragonal system, belong to I41/a(88) space groupstructure. The diffraction peaks moved towards smaller angle withincreasing diameter of the metal cations. Doping different rare earth hasan influence on the luminescence. Eu3+-doped samples can be excited bythe near-UV (393nm), the main emission peak at614nm, redfluorescence. Tb3+-doped samples can be excited by the near-UV (260nm), the main emission peak at546nm, green fluorescence. Under the same conditions, the average crystallite size of CaWO4after doped wasthe smallest and luminescent property was the best.The samples were obtained atdifferent calcination temperatures. By SEM, the nano-microspherparticles about100-300nm in diameter are synthesized after400℃calcinated. When calcination temperature is600℃, the microspherparticles are about2-6um in diameter, so the calcination temperaturealso have some impact to the dispersion of tungstate samples. Withthe change Caâ†'Sr, this characteristic is especially obvious. However,in a certain range, the luminescent property of samples calcinated byhigh temperature is better.