YAG: Eu and YAG: Pr microspheres for high-power LED color converters
GHADAMYARI M. 1, BULGAN G. 2, PARCHOVIANSKY M. 1, KLEMENT R. 1, GALUSEK D. 1,3, MICHALKOVA M. 3
1 FUNGLASS – CENTRE FOR FUNCTIONAL AND SURFACE FUNCTIONALIZED GLASS, Trencin, Slovakia; 2 Swiss Federal Laboratories for Materials Science and Technology (Empa), Zurich, Switzerland; 3 Vitrum Laugaricio – Joint Glass Centre of the IIC SAS, TnU AD, FChPT STU and RONA, a.s., Trencin, Slovakia
Inorganic color converters known as "phosphor-in-glass" (PiG), which combine transparent glass and ceramic phosphors, have been commercialized, utilizing their many advantages (wLEDs). However, LEDs are still plagued by several flaws such as low emissivity in the red region and a low efficiency.
In this work, a phosphor powder in the form of YAG: Eu/Pr microspheres was prepared by flame synthesis followed by crystallization. The second step was to match the refractive index of prepared ceramic phosphor with glass matrix. For this purpose, two glass matrices were selected: Bi2O3-B2O3-ZnO and Si2O-LiO-ZnO-WO3-La2O3-Bi2O3 and the ratios of individual components were optimized to match the refractive index of glass with the refractive index of YAG matrix. The process of homogeneous incorporation and distribution of ceramic phosphor microspheres in the glass matrix was optimized.
The influence of glass matrix composition and processing conditions on photoluminescence and color coordinates of prepared materials are critically discussed.