Research On Preparation Of Well-Crystallined And Small Size Yag Particles By Alumina Template Method

White LEDs have been one of the most famous green light sources. Due to its advantages of energy-saving, environmental protection, long life, small size, fast response, etc, white LEDs have a broad prospect in application. The YAG phosphor of white LEDs has a strong impact on the performances of white LEDs. Currently, commercial YAG phosphor is produced with traditional high-temperature solid-state reaction method, with large particle size and wide distribution. Although the molten salt is often used in the particular crystal growth promotion, but collaboration with phosphor still lack practice. This paper studied the molten salt technology for YAG phosphor preparation. We used monocrystal aluminum oxide as a template to prepare YAG phosphor of small size particle.α-Al2O3 powder with small particle size is prepared by chemical precipitation method. The parameters such as stirring speed, accelerant, dispersant and heating process are analyzed and optimized, which affect particle size and morphology of α-Al2O3. As a result, it is found that high stirring speed would decrease particle size of α-Al2O3 powder. Appropriate accelerant would change the shape of α-Al2O3 to flake. Finally α-Al2O3 powder with 3μm particle size, good dispersity is prepared. Then we prepare the nanoparticles of Y2O3 with chemical precipitation method. It is found that the precipitant of bicarbonate is better than the urea. Eventually, the Y2O3 powder with 100nm particle size is prepared.In this paper, we used molten salt method to prepare small particles of YAG. The parameters such as diferent molten salt system, calcination temperature are investigated. Also we optimized the preparation process and found the three-step molten salt method. First we obtained the structure of alumina particles surrounded by yttrium oxide because of the template of Al2O3, with molten salt NaCl at 900℃, then fired it with molten salt KCl at 1200℃. Finally it was transformed into YAG with molten salt K2SO4 at 1400℃ entirely. YAG and α-Al2O3 are very similar in the morphology and the particle size.This paper analyzed the mechanism of template synthesis to prepare YAG of small particle size:in molten salt, yttrium oxide nanoparticles moves to the surface of monocrystal α-Al2O3 particle and reacts to form package structure; generates a mesophase Y4Al2O9 at lower temperature, and further generates an intermediate YAlO3, finally YAP phase reacts with Al2O3 phase to YAG phase.