Preparation, structure and luminescence properties of Ce3+: Y3(Al,Ga)5O12 translucent glass ceramics for AC-LEDs

Translucent glass ceramics containing Ce3+:Y-3(Al,Ga)(5)O-12 microcrystals were prepared by spontaneous crystallization in the SiO2-B2O3-Al2O3-Ga2O3-Y2O3-PbO-CeF3 glass system. The sample exhibits around 45 % transmittance in the range of 500-800 nm. X-ray diffraction patterns confirm the garnet phases. Scanning electron microscope and laser scanning confocal microscopy images suggest that about 5 mu m grains are dispersed uniformly in the glass matrix. With increasing Ga/Al ratio in the components, both excitation and emission peaks blue shift. The emission intensity reaches to the maximum at Ga/Al ratio of 8/22, and the optimized Ce3+ content is 0.4 mol%. The sample exhibits yellowish-green persistent luminescence with lifetime of 47.3 ms. The glass ceramic-based device exhibits near standard white light emission with luminous efficiency of 64.7 lm/W, correlated color temperature of 6979 K, color rendering index of 65.4 and flicker index of 76.9 %. It indicates that the Ce3+:Y-3(Al,Ga)(5)O-12 glass ceramics are promising in the alternating current directly driven white light-emitting diodes (AC-LEDs).