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Preparation Of High Luminescent Efficiency And Small Size YAG:Ce Phosphor By Molten Salt Method

Posted on:2017-12-27Degree:MasterType:Thesis
Country:ChinaCandidate:W Q YuFull Text:PDF
GTID:2311330491464106Subject:Materials Science and Engineering
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White LEDs have been the new generation of green lighting source for their advantages of energy conservation, environmental protection, long service life, simple structure and small volume. The luminescent materials YAG:Ce3+ phosphors have a great influence on the performance of white LEDs. Currently, the commercial YAG: Ce3+ phosphors are prepared by high temperature solid-state reaction method. They have high crystallinity, but large particle size and wide distribution.It would bring about problems such as quick settling velocity, complex packaging progress, huge phosphor powder dosage, seriously affecting the light color consistency and product uniformity of white LEDs. So it is urgent to synthesize YAG:Ce3+phosphors of small size and high luminous efficiency. This paper tries to prepare YAG:Ce3+phosphors by molten salt method. The parameters such as raw materials composition and calcination factors were discussed. The synthesis mechanism of YAG:Ce3+ phosphors had been explored.We used molten salt method to synthesize YAG with ?-Al2O3 and homemade Y2O3(Ce) as raw materials. The parameters such as particle size of ?-Al2O3, calcination temperature, molten salt species, salt to material ratio and Y2O3 were investigated. As a result, it is found that choosing the smaller particle size of ?-Al2O3 is more likely to prepare small size YAG. The mesophase Y4Al2O9(YAM) and YA1O3(YAP) are generated at low temperature. YAM would disappear and YAP increase as the temperature rise. Finally YAP reacts with ?-Al2O3 to YAG. Small size and good dispersion of YAG were prepared in Na2SO4 and K2SO4 with high salt ratio. Nanometer Y2O3(Ce) would be the better raw materials.We also synthesized YAG with ?-Al2O3 and homemade nanoscale Y2O3(Ce) as raw materials by molten salt method. The paremeters such as calcination temperature and time, composition of raw materials, molten salt purity and mixing mode were studied. Also we discussed the reaction mechanism. It is found that higher temperature and appropriate time could have benefit to the luminescent efficiency of YAG. Changing the raw material composition would reduce the efficiency and dispersion of YAG. Using guarantee reagent KCl molten salt would synthesize higher efficiency YAG phosphors than using analytically pure KCl. Contrast with wet mixing and wet grinding mixing way, the dry mixing way could prepare high efficiency YAG phosphors.The reaction process of ?-Al2O3 and homemade nanoscale Y2O3(Ce) can be divided into three stages.First, ?-Al2O3 reacts with Y2O3 into YAM at low temperature. Then, YAM reacts with ?-A12O3 into YAP. Finally, YAP reacts with y-Al2O3 into YAG at high temperature.In this paper, we successfully synthesized 2-3?m and 93% luminescent efficiency compared with commercial YAG:Ce3+ phosphors by the molten salt method, using ?-Al2O3 and homemade nanoscale Y2O3(Ce) as raw materials.
Keywords/Search Tags:White LEDs, YAG:Ce3+ Phosphors, Molten Salt Method, Small Particle Size, High Luminescent Efficiency
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