| Rare earth luminescent materials have been widely used in lighting, display imaging, solid-state lasers, optical storage and optical communication and other fields. In recent years, the research of rare-earth-doped substrate materials for improving the luminous efficiency, mechanical properties, chemical stability and life become a research hotspot in the field. Alumina has high mechanical strength, good thermal conductivity, chemical stability and good transparency, and draws many researchers' attention. At present, the nanocrystallization of the powder and its dispersion, as well as the transparent substrate film are two important directions.In this paper, the Al2O3 was used as the rare earth ions doped substrate, the sol-gel preparing process of Al2O3 was studied, with emphasis on the preparation of the laws of Al2O3 sol, Al2O3 nanocrystlline powder dispersion and the transparency of Al2O3 films. Based on that, the photoluminescence properties of Eu3+ doped and Tb3+ doped Al2O3 nanocrystalline powders and their transparent film were investigated. The major research contents and the conclusions were as follows:1. The preparation of Al2O3 sol were carried out. The results show that the hydrolysis temperature will affect the grain size of sol formation and growth process. When the hydrolysis temperature is 60-80℃, the stable boehmite (γ-AlOOH) structure sol can be obtained; with extended aging time, the sol viscosity increased, the original small particles of the sol gradually grow together to form the fibrous particles with the length of 50nm; the type and the concentration of the acid will change the charge-environment of the sol system and the double-layer structure of the sol surface, the appropriate addition of strong acid (pH= 2.73～3.20) was in favor of the sol stability; the increase in the amount of water can promote precursor hydrolysis, and is conducive to improve the crystallization of the boehmite sol. Furthermore, adding the surfactant can effectively reduce the aggregation between the sol particles to enhance the stability of sol. 2. The preparation of Al2O3 nanocrystalline powder was carried out. The results showed that the mixed solvent and surfactant (PEG 1000) can be an effective solution to the combined effect of Al2O3 nanocrystalline powder reunion. In the process of calcination decomposition. PEG1000 reduce the Al2O3 ion diffusion between the grains and improve the Al2O3 nanocrystalline powder dispersion. With the increasing of the heat treatment temperature, Al2O3 had the phase transformation process ofγ-AlOOH→γ-Al2O3→θ-Al2O3→α-Al2O3, and the grain size is reduced firstly and then incline to increase.3. The preparation of transparent Al2O3 film was carried out. The results showed that the light transmittance of the Al2O3 film is closely related to the microstructure. Al2O3 films grain growth of the preferred orientation of the film significantly reduce the reflection coefficient (M) and scattering coefficient (S), to improve the film transmittance; calcination led to the film gradually reduce the oxygen vacancy, and has reduced the absorption of light. After calcined at 800℃, the optical transmittance was maximum; and calcined at 900℃, theθ-Al2O3 generated in the films resulted in lower light transmittance.4. The photoluminescence properties of Eu3+ and Tb3+ doped Al2O3 nanocrystalline powders and their transparent films were analysed. The results show that the average grain size of the nanocrystalline luminescent powder was about 10 nm, with granular particles, good dispersion and good transparency, and the surface is dense and smooth without cracks. Luminescence properties of the materials were mainly affected by the calcination temperature and doping concentration. The best calcination temperature is 800℃, the doped concentration of Eu3+ is 10 mol%, the doped concentration of Tb3+ is 5 mol%.
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