| The Eu2+ and Dy3+ activated SrAl2O4 phosphor is a kind of energy-storing materials. The materials can absorb the visible light, store the energy, and then release the energy as visible light which leads to long lasting afterglow in the darkness. Recently, this type of phosphor has excellent properties such as chemical stability, great luminance, long duration, no damaging radiation. These properties result in a wide application of the materials in many fields. Although, this afterglow phosphor is chemically stable in most cases, it is liable to hydrolyze in water, and thus can not be used in a water-containing environment.In the present paper, SrAl2O4:Eu2+, Dy3+ phosphor powders were coated with different films such as SiO2, Al2O3 and mullite by sol-gel process. These films suppress the hydrolysis reaction of the phosphor in water-containing environment. First, characters of the films were determined and factors which affecting the films, such as reacting temperature, pH, concentration, were studied. The results show that the best experiment conditions for SiO2 film using as precursor were as following:pH 10; temperature 85℃; coating time1.5h. When it comes to Si(OC2H5)4(TEOS) as precursor, the best experiment conditions were:nTEOS:n CH3CH2OH:nH2O:nHCl=1:5:10:0.03; temperature 80℃; coating time2h. The best experiment conditions for Al2O3 film were as following:pH 3～4; temperature 70℃～80℃; coating time1.5～2h. And for mullite film, the best experiment conditions were:①pH 2～3;②temperature 70℃～80℃;③coating time1.5～2h.Then, through different experiment, the films were studied by SEM, IR spectra, and coating process and mechanism were concluded.Finally, though the analysis and comparison, it has been found that all of the there films can suppress hydrolysis. But the mullite film and SiO2 film prepared by TEOS had the best result such as better water-resistance performance and persistent luminescent properties. But it took quite a few hours to get the mullite sol.
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