Preparation And Properties Of The White Led Used Yellow Yag Phosphor

White light-emitting diode (LED) is recognized as the most valuable green light source in the 21st century. In the near future it will replace incandescent and fluorescent lighting to become dominant of the light market. Therefore, white LED becomes the competing development objective of the world's research institutions around the lamps and light sources, and governments have also given great support. At present the majority of the commercial white LED use light conversion method. As the YAG phosphor coating on the surface of blue LED chips, blue light excites the phosphor, which issued a yellow phosphor. Then the two light mix into white light. As the core technology, the phosphor plays an important role in the light-emitting devices. So the study of phosphors becomes particularly important.In this paper, the light-emitting performance of phosphors is studied, and the results are as follows:(1) Using soft-chemistry method—sol-gel method to carry out experiments, yttrium aluminum garnet (YAG) phosphor with good light-emitting performance were successfully prepared. Factors as the sintering temperature, the ratio of citric acid and metal ions, Ce doping were discussed how to affect the samples'performance. It is obtained that the sample has begun to form YAG phase at 900℃. The best ratio of citric acid and metal is 1:1.(2) Combining microwave technology and sol-gel method, a series of YAG phosphor samples were prepared. From the spectroscopic properties, XRD, infrared spectral analysis, the best synthesis process is found: sintering temperature is 1000℃; microwave power is at low to medium fire with 230W; microwave time is 3min. Through the SEM and laser particle size analysis of samples, the average particle size is from 1.352μm to 3.681μm. Compared with the commercial phosphor, whose average particle size is 15μm, the homemade samples are greatly small. This would be conducive to the improvement of phosphor coating.(3) The prevalent problem of phosphors is the low color-rendering index. To improve this issue of deviating from the center of white color coordinates, four kinds of rare-earth ions Gd, La, Sm, Pr were doped. Experimental results show that: when the calcination temperature is 900℃, the sample can form pure YAG phase. Joining four kinds of rare earth ions Gd, La, Sm and Pr can cause phosphor emission spectra red-shift or increase the red spectral components.(4) The phosphor samples with excellent performance were made by coprecipitation. With the sintering temperature reaching to 900℃, the samples showed a very good map of YAG phase. After electric light and colors comprehensive performance test of samples, the best luminescence properties of phosphors occurred at the Ce concentration of x=0.05.