Micropowder CaYMgScSiO:Ce Silicate Garnet as an Efficient Light Converter for White LEDs.

This work is dedicated to the crystallization and luminescent properties of a prospective CaYMgScSiO:Ce (CYMSSG:Ce) micropowder (MP) phosphor converter (pc) for a white light-emitting LED (WLED). The set of MP samples was obtained by conventional solid-phase synthesis using different amounts of BO flux in the 1-5 mole percentage range. The luminescent properties of the CYMSSG:Ce MPs were investigated at different Ce concentrations in the 1-5 atomic percentage range. The formation of several Ce multicenters in the CYMSSG:Ce MPs was detected in the emission and excitation spectra as well as the decay kinetics of the Ce luminescence. The creation of the Ce multicenters in CYMSSG:Ce garnet results from: (i) the substitution by the Ce ions of the heterovalent Ca and Y cations in the dodecahedral position of the garnet host; (ii) the inhomogeneous local environment of the Ce ions when the octahedral positions of the garnet are replaced by heterovalent Mg and Sc cations and the tetrahedral positions are replaced by Si cations. The presence of Ce multicenters significantly enhances the Ce emission band in the red range in comparison with conventional YAG:Ce phosphor. Prototypes of the WLEDs were also created in this work by using CYMSSG:Ce MP films as phosphor converters. Furthermore, the dependence of the photoconversion properties on the layer thickness of the CYMSSG:Ce MP was studied as well. The changes in the MP layer thickness enable the tuning of the white light thons from cold white/daylight to neutral white. The obtained results are encouraging and can be useful for the development of a novel generation of pcs for WLEDs.