Preparation Of High Luminescent Efficiency And Small Size YAG

White LEDs has many advantages such as energy saving,long service life,simple structure,small size,etc.It has been widely used in various fields of production and life.Now the mainstream of the white LEDs technology is based on the blue-emitting GaN chip-based light source to stimulate YAG:Ce3+ yellow phosphors emission yellow light,blue and yellow light combination to get white.Therefore,the particle morphology,particle size and distribution and luminous properties of YAG:Ce3+ phosphors will have a significant impact on light-emitting performance of white LEDs.At present,commercial YAG:Ce3+ phosphors are mainly prepared by traditional high-temperature solid-state reaction method..The phosphors particles prepared by this method are large in size(generally 10 microns or more)and irregular in particle shape and non-uniform in particle size.The color uniformity and product consistency of white light LEDs are affected.In this paper,the YAG:Ce3+ yellow phosphor with small particle size and high efficiency is prepared by the molten salt method.The effect and synthesis principle of the fluoride in the molten salt method and the firing parameters are studied in order to further improve the luminescence of the white LEDs performance.In this paper,YAG phosphor was prepared by using ?-Al2O3 and nanoscale Y2O3(Ce)as raw materials.The phase and particle morphology of YAG phosphors that prepared by molten salt method were investigated.It was found that YAM(Y4Al2O9)and YAP(YAlO3)phases were formed when the raw materials ?-Al23 and Y2O3(Ce)were formed at low temperature without addition of fluoride.At higher temperature,the YAM phase changed to YAP phase and YAG phase,The pure YAG phase is formed at 1300 ?,the particle size is submicron and the dispersity is better.After adding 5%wt AIF3,the pure YAG phase is formed at 900 ?,and the particle size is larger,about 10 microns.In this paper,the YAG phosphors was prepared by y-Al2O3 and nanoscalc Y2O3(Cc)as the raw materials.The effects of the three kinds of fluoride(AIF3,NaF and KF)on the morphology and luminescent properties of YAG:Ce3+ phosphors were investigated.It was found that the particle size of the YAG:Cc3+ phosphors increased with the addition of fluoride and the particle size of YAG:Ce3+ phosphors was increased with the addition of fluoride The quantum efficiency of the YAG:Ce3+ phosphors increases first and then decreases.After adding 5%wt AlF3,the pure YAG phase is formed at 900 ?.Without fluoridc,The reaction process of y-Al2O3 and nanoscale Y2O3(Ce)can be divided into three stages.Firstly,?-Al2O3 reacts with Y2O3(Ce)into YAM at low temperature.Then,YAM reacts with ?-Al2O3 into YAP.Finally,YAP reacts with ?-Al203 into pure YAG at 1400 ?.YAG:Ce3+ phosphors with high efficiency of small particle size were prepared by the two-step method.The properties of the YAG:Ce3+ phosphors were studied by the improved preparation method.The effects of reduction temperature and reduction time on the particle morphology and luminescence properties of the two intermediate products were investigated.It was found that the luminescent properties of the YAG:Ce3+ phosphors could be improved with the smaller size.The higher reduction temperature and the longer reduction time of the YAG:Ce3+ phosphors will caused bigger particle size and more agglomeration in the second step.The luminescent property of the YAG:Ce3+ phosphors will increase first and then decrease with the increase of the reduction temperature and the reduction time.