Y2O3-YAG:Ce composite phosphor ceramics with enhanced light extraction efficiency for solid-state laser lighting

Abstract

Due to high thermal conductivity and excellent laser irradiation resistance, composite phosphor ceramics (CPCs) have been widely acknowledged as ideal color converters in laser lighting. However, achieving high-efficiency laser lighting is significantly limited by the inefficient utilization of pumping light. Microstructural tailoring is recognized as a promising strategy to improve the light extraction efficiency, while it is restricted by the harsh preparation conditions. Herein, we propose a novel Y₂O₃-YAG:Ce CPC controllably prepared from mesoporous Y₂O₃ powders and YAG:Ce phosphors using spark plasma sintering at a low temperature of 1160 °C. Attributed to the introduced Rayleigh scattering centers tailored by fine ceramic grains and well-matching of refractive indexes between the phosphor and the matrix, the Y₂O₃-YAG:Ce CPC exhibits an ultra-high relative internal quantum efficiency of 107% compared to that of the YAG:Ce phosphor. Impressively, when irradiated under a 450 nm laser diode, the as-prepared CPC produces white light with a high luminous efficiency of 178.42 l m W⁻¹ and a low correlated color temperature of 4638 K, reflecting the enhanced light conversion efficiency. Furthermore, the CPC presents a remarkable improvement in thermal stability (only 6% luminescence loss at 200 °C) and is able to withstand a high laser flux density up to 6.16 W mm⁻². These results demonstrate that the optimized Y₂O₃-YAG:Ce CPCs with designed microstructures are well suited for solid-state laser lighting with high power and brightness.