Direct synthesis of spherical YAG:Ce phosphor from precursor solution containing polymer and urea

In this study, spherical cerium-doped yttrium aluminum garnet (YAG:Ce) phosphor particles were directly synthesized by a modified sol-gel method using poly(ethylene glycol) (PEG) and urea. In the absence of PEG and urea, only irregularly shaped particles were obtained through aggregation and sintering after solvent evaporation. In contrast, adding both PEG and urea to the precursor solution resulted in the formation of spherical particles. The spherical morphology was attributed to micellization by PEG and micelle agglomeration by urea in a liquid phase. Scanning electron microscopy and X-ray diffraction analyses revealed that the spherical particles were of size around 5 mu m, and the obtained crystal was pure a YAG phase. The emission band of the YAG:Ce phosphor prepared at 1600 degrees C for 2 h was observed at 530 nm under excitation at 470 nm, and the maximum internal quantum efficiency was found to be 57.6%. (C) 2012 Elsevier B.V. All rights reserved.