Effect of metal halide fluxes on the microstructure and luminescence of Y3Al5O12:Ce3+ phosphors

Yellow-emitting Y2.95Al5O12:0.05Ce (YAG:Ce) phosphor particles with high luminescence efficiency under 450 nm ultraviolet (UV) excitation were prepared by a heat treatment of submicrometer-sized oxide powder mixture in a reducing atmosphere at 1550 degrees C. Prior to the heat treatment, the oxide mixture was blended with 5 wt% of metal halides - BaF2, BaCl2, NaF, NaCI, and KF - as a flux. It was observed that YAG:Ce particles prepared with fluorine containing flux demonstrated spherical morphology, high photoluminescence properties, and diameters of 5-20 mu m, whereas those prepared with chlorine were small-sized particles (<= 5 mu m) with relatively low intensity. The highest relative photoluminescence (PL) intensity (similar to 118%) was obtained for the samples prepared with 5% BaF2. A set of rules was established for the formation of spherical YAG:Ce particles in the presence of this flux. (C) 2011 Elsevier B.V. All rights reserved.