Abstract:

Solid-state laser lighting fabricated by combining blue laser diodes (LDs) and yellow-emitting phosphor converters has attracted great attention in high-luminance applications. However, the achievement of high-power laser lighting is significantly affected by the thermal quenching effect of phosphor converter materials. Therefore, component regulation and performance optimization are required to improve the thermal conductivity and luminescence uniformity of phosphor converters. In this work, a series of Al₂O₃-YAG:Ce composite ceramic phosphors with different Al₂O₃ contents were prepared by solid-state reaction sintering. The influences of Al₂O₃ contents on the microstructure, phase composition, optical properties and thermal performance of the Al₂O₃-YAG:Ce ceramic phosphors were investigated in detail. The total transmittance of the Al₂O₃-YAG:Ce ceramic phosphors at 800 nm tends to decline (82.6%→23.6%) with the increase of Al₂O₃ content (0→90%, weight ratio). Both excitation and emission intensity of the Al₂O₃-YAG:Ce ceramic phosphors initially increase and then decrease with increasing Al₂O₃ content. When the weight ratio of Al₂O₃/Al₂O₃-YAG:Ce is 70%, the ceramic phosphor exhibits a high thermal conductivity of 25.7 W·m^-1·K^-1 at room temperature and the highest emission intensity. A high luminous flux of 3724 lm and luminous efficacy of 239.4 lm·W^-1 are obtained when pumping the 70% Al₂O₃-YAG:Ce ceramic phosphor with blue LDs at a power density of 20 W·mm^-2. Additionally, the luminous efficacy only decreases by 10.5% and the luminous flux continues to increase without showing luminescence saturation, when the power density increases from 1 W·mm^-2 to 20 W·mm^-2. Therefore, the Al₂O₃-YAG:Ce composite ceramic phosphors are promising in high-power laser lighting for excellent luminous efficiency and improved thermal stability.

Key words: Al₂O₃-YAG:Ce, laser lighting, luminous efficacy, component regulation, performance optimization