To synthesize nanosize phosphor particles with high luminescence efficiency under UV light, organic additives such as citric acid and ethylene glycol and flux were introduced in large-scale spray pyrolysis. phosphor particles prepared from solution with polymeric precursors such as citric acid and ethylene glycol had micrometer size and spherical shape. However, particles prepared from polymeric precursor solution with flux were nanosize and had nonaggregation characteristics. The as-prepared spherical particles with micrometer size turned into nanosized particles during post-treatment by recrystallization process. The nanosized phosphor particles showed high brightness under 254 nm UV light. The photoluminescence (PL) intensity of the particles prepared from polymeric precursor solution with flux material and post-treated at 1050°C, which are nanosize and have nonaggregation characteristics, was identical to 109% of that of the commercial product. The particles post-treated at 1150°C had a PL intensity 34% higher than the commercial product while showing aggregated characteristics. © 2003 The Electrochemical Society. All rights reserved.