High luminous efficiency and high saturation threshold in highly transparent LuAG:Ce phosphor ceramics for laser diodes lighting.

ABSTRACT

Lu3Al5O12Ce (LuAGCe) phosphor ceramics (PCs) with the excellent thermal stability and high saturation threshold are considered as the best green-fluorescent converters for high-power laser diodes (LDs) lighting. In this study, the effects of sintering additives and sintering processes on the transmittance and microstructure of LuAGCe PCs were systematically studied, and the luminescence performance of ceramics with different transmittance was compared. LuAGCe PCs with the transmittance of 80% (@800 nm, 1.5 mm) were obtained by using 0.1 wt.% MgO and 0.5 wt.% TEOS as sintering additives, combined with optimized vacuum pre-sintering and hot isostatic pressing. Compared to the non-HIP samples, the transmittance had increased by 11%. The microstructure of ceramics indicated that high transparency was closely related to the decrease in intergranular pores. Notably, the luminous efficiency of 253 lm/W and its saturation thresholds of > 46 W/mm2 were obtained simultaneously in green-emitting LDs devices. Moreover, under 3W laser irradiation, highly transparent ceramics had the low surface temperature of 66.4 °C, indicating the good heat dissipation performance. The observed high luminous efficiency and high saturation threshold of LuAGCe PCs were attributed to fewer pores and oxygen vacancies. Therefore, this work proves that highly transparent LuAGCe PCs are promising green-fluorescent converters for high-power LDs lighting.