Hydrolysis mechanism and method to improve water resistance of long after-glow phosphor

Hydrolysis mechanism of long afterglow phosphor and the method to improve the water resistance are presented using SrAl₂O₄:Dy,Eu phosphor as an example. The phosphor with high brightness and long afterglow is liable to hydrolyze in water to form Al₂O₃ and Sr₃Al₂(OH)₁₂ because of the crystal structure, and thus the luminescent property decreases. A thin silica film is coated on the surface of the phosphor using a sol-gel process. The silica film acts as a barrier between water and phosphor, and thus suppresses the hydrolysis reaction.