Europium-doped yttrium aluminum garnet (YAG) particles were modified by the ultrasonic spray pyrolysis of colloidal solutions. To obtain the high brightness of Y2O3 : Eu and the high stability of YAG: Eu, we put the Y2O3 : Eu phosphor in YAG: Eu particles. The colloidal spray solution was prepared by adding the submicrometer-size Y2O3 : Eu particles, which were prepared by the filter expansion aerosol generator process, into YAG: Eu aqueous solution. The brightness of the modified YAG: Eu particles was increased by about 30% compared with the pure YAG: Eu particles, and the modified YAG phosphor showed increased cathodoluminescence (CL) in all excitation voltage ranges. The saturation tendency at the high current excitation was improved as thickness of the YAG layer was increased. (C) 2004 The Electrochemical Society.