Synthesis Of YAG: Ce Phosphor Powders

Ce-dopted Yttrium Aluminum Garnet(YAG) Phosphor is regarded as the key material for the white LED application, its quality contributes to the properties of white LED remarkably, such as luminance intensity, working life, etc. The main synthetical methods of YAG phosphor include solid state reaction, co-precipitation , sol-gel, combustion, etc. Solid state reaction is a popular method for YAG phosphor because of its low cost and simple technique.YAG: Ce precursors were synthesized by a coprecipitation method with the solutions of mixed nitrates as starting materials and AHC as the precipitator. The precursors and the powders sintered at various temperatures were characterized by infrared spectra (IR), X-ray diffractormetry (XRD), transmitted electron microscopy (TEM) and so on. The photoluminescence spectra of YAG: Ce nano-powders was measured. The results show that pure YAG phase can be obtained at 1 100℃and YAP and YAM intermediate phases were not detected. The sintered powders are well dispersed and less aggregated under the temperature of 1 100℃, and XRD, TEM and the BET surface analysis show that the particle diameters of the nano-powders were about 40-80 nm. The fluorescence spectra show that YAG: Ce powders has good photoluminescence.YAG precursors were synthesized with low cost by a mixed solvothermal method. The precursors were prepared by using NH4HCO3 as the precipitant, and pure-phase YAG with diameter of 100-160 nm, well-dispersed and spherical morphology were obtained by heated at 210℃for 15 h without any other intermediate phase.The YAG:Ce phosphors were synthesized via mixed solvothermal method, using ethylenediamine- ethanol as solvent, performed based on the study of synthesizs conditions of YAG powders. The results show that the pure-phase YAG: Ce with spherical morphology can be synthesized under 210℃for 15h as the precipitants without the processes of washing and drying. The excitation spectra of YAG: Ce phosphors have two peaks. The major one is around 450 nm attributed to the 4fâ†'5d transitions. Its emission band is wide with the peak at 530nm and it belongs to the 5dâ†'4f transitions. Ce³⁺ ions act as the activation in the phosphors, they effect theluminescent properties of YAG: Ce phosphors. The formation mechanism of synthesized YAG: Ce phase was discussed on the basis of the research above. At last, we studied the effect of polymer-assisted on the formation, morphological control and luminicence propertise of YAG: Ce powders.We chose polyethylene glycol, gum acacia and poly vinyl alcohol as polymer-assist. The results show that the YAG: Ce powders with diameter of 20-30 nm, well-dispersed and good photoluminescence were synthesis by using polyethylene glycol as assist. The powders can be used as the phosphor of LED,and have good potential application of fluorescence-labelled。...