YBO3 : Tb fine particles with high photoluminescence were prepared by a spray pyrolysis process. The emission intensity of YBO3 : Tb particles under vacuum ultraviolet (VUV) excitation was optimized by controlling the Tb content, excess quantity of boron, and heat-treatment temperature. The highest luminescent intensity under VUV excitation was obtained when 10 atom % Tb with respect to yttrium and 25% excess boron of the stoichiometric quantity were used at 1150 degreesC post-treatment temperature. It was tried to simultaneously control the morphological and luminous properties of YBO3 : Tb particles via the modification of the precursor solution to be sprayed. The YBO3 : Tb particles prepared from a nitrate aqueous solution which was obtained by only dissolving yttrium nitrate, terbium nitrate, and boric acid in purified water showed rod-like morphology. When the nitrate aqueous solution was modified by NH4OH, however, the prepared particles had not only a spherical-like shape, but also fine and more uniform size distribution than the rod-like particles prepared and the commercial YBO3 : Tb particles. In addition, the YBO3 : Tb particles prepared from the NH4OH-assisted spray solution showed improved luminescent intensity compared with the particles with a rod-like shape. From X-ray diffraction analysis, it was found that an enhancement of the crystallinity of YBO3 : Tb was achieved by using NH4OH as a chemical additive. Finally, the photoluminescence intensity of YBO3 : Tb particles optimized in terms of the composition, heat-treatment condition, and morphology was higher than that of the commercial YBO3 : Tb particles as well as Zn2SiO4 : Mn. (C) 2004 The Electrochemical Society.