Microstructure tailoring of red-emitting AlN-CaAlSiN3:Eu2+ composite phosphor ceramics with higher optical properties for laser lighting

Abstract

Laser lighting is superior to light-emitting diodes (LEDs) in brightness, beam aperture and efficiency, which largely depends on the light extraction efficiency and thermal properties of color converters. In this paper, we proposed to improve the light extraction efficiency of red-emitting AlN-CaAlSiN3:Eu composite phosphor ceramics by controlling the light scattering, and to improve the thermal conductivity of the phosphor ceramics by increasing grain size. The composite phosphor ceramics with moderate light scattering and high thermal conductivity can be obtained by gas pressure sintering (GPS) and the followed hot isostatic pressing (HIP). The saturation threshold of the sample is increased from 7.0 to 10.8 W, and the luminous flux is enhanced from 32.3 to 51.0 lm after the HIP post-treatment, which is 55.5% higher than the previously reported dense AlN-CaAlSiN3:Eu composite phosphor ceramics (32.8 lm). This work emphasizes the role of pore size distribution in light extraction efficiency of phosphor ceramics.