The influence of the precursor types of phosphorus such as (NH4)(2)HPO4, NH4H2PO4, (NH4)(3)PO4, and H3PO4 on the morphology and vacuum ultraviolet (VUV) characteristics of GdPO4:Tb phosphor particles prepared by spray pyrolysis was investigated. All prepared GdPO4:Tb phosphor particles had spherical shape and dense structure except for the sample prepared with H3PO4, which had hollow morphology after the 3 h post-treatment anneal at 1050degreesC. The phosphorus type also affected the photoluminescence (PL) intensity of GdPO4:Tb phosphor particles. The highest PL intensity under VUV excitation was obtained with (NH4)(2)HPO4 used as the precursor. For optimizing the PL intensity of spherical particles, the average particle size of GdPO4:Tb phosphor particles prepared using (NH4)(2)HPO4 was changed from 0.5 to 1.9 mum and the effect on PL intensity was investigated. The optimized GdPO4:Tb particles have a good excitation spectrum comparable to that of the commercial Zn2SiO4:Mn phosphor particles under VUV illumination from 140 to 220 nm. (C) 2002 The Electrochemical Society.