Abstract: Hydrolysis in alkaline condition and inferior temperature resistance property were two disadvantages of SrAl2O4:Eu2+,Dy3+(SrAl2O4) long persistence phosphors.To address these two issues, this study has employed ethylene glycol as a non-aqueous reaction medium to cover a SiO2 layer on the SrAl2O4 surface. This strategy effectively isolated the SrAl2O4 matrix from water molecules, and hence avoiding the side hydrolysis reactions during the coating process. After careful study, the optimized coating process was determined as: solution pH value was 11.0, reaction temperature was 80.0 ℃, reaction time was 2.0 h, Na2SiO3 dosage was 6.0%(mass fractoin) of SrAl2O4 powders. Under the optimized condition, a dense SiO2 layer with the thickness of 60 nm was seamlessly coated on SrAl2O4 surface, leading to a SrAl2O4@SiO2 core@shell composite. According to X-ray diffraction pattern, the crystal phase of the SrAl2O4 was not changed during the coating process. Compared to the pristine SrAl2O4, the luminescence intensity of composites was only reduced 11.2%, while the anti-hydrolysis property was largely improved. In practical application, the bright green color could be easily observed by naked eyes after washing 6.0 h in the presence of detergent. The thermogravimetric analysis indicated the remained weight of SrAl2O4@SiO2 composites was 93.7%(mass fraction) after calcinated at 800 °C. This study provided a novel way to improve the anti-hydrolysis property and high-temperature resistance property of SrAl2O4 without remarkably sacrificing their luminescence property, and this was beneficial for their real application in fire protection.

Key words: Surface modification; Luminescent material, Core@shell structure, Anti-hydrolysis property, Thermal stability