A spray drying approach was used to coat 15 nm SiO2 continuous films onto ZnS:Ag phosphor particles. The coating was deposited on the particles by simultaneously spraying a slurry consisting of a solution of TEOS and ethanol with the solid phosphor particles into a heated drying column. The cathodoluminescent spectra of silica coated phosphor has CIE 1931 chromaticity coordinates of X similar to 0.055, Y similar to 0.085, brightness that is 90% of the uncoated phosphor brightness, and improved aging behavior under laboratory testing conditions. (c) 2005 Springer Science + Business Media, Inc.