Stable, Heat-Conducting Phosphor Composites for High-Power Laser Lighting

Area of Science:

• Materials Science
• Solid-State Lighting
• Photonics

Background:

• Laser diodes in solid-state lighting generate high light fluxes, leading to phosphor self-heating and conversion losses.
• Current silicone-based encapsulation strategies are insufficient for managing the thermal demands of high-flux laser-driven lighting.

Purpose of the Study:

• To develop a rapid method for preparing robust ceramic phosphor composites for laser diodes.
• To investigate the impact of composition and microstructure on thermal and luminescent properties.
• To evaluate the performance of these composites in laser-driven white lighting applications.

Main Methods:

• Utilized spark plasma sintering (SPS) for rapid fabrication of ceramic phosphor composites.
• Composed composites of cerium-doped yttrium aluminum garnet (Ce:YAG) and aluminum oxide (α-Al2O3).
• Studied the effects of compositional modulation, phase fraction, and microstructure on material properties.

Main Results:

• SPS enabled detailed study of compositional effects on phase, microstructure, and luminescence.
• Established a relationship between composite density, thermal conductivity, and reduced temperature rise during laser excitation.
• Achieved >1000 lm luminous flux using a single laser diode and phosphor element in reflection mode, with excellent color uniformity due to Lambertian scattering.

Conclusions:

• Ceramic phosphor composites prepared by SPS offer a viable solution for thermal management in laser-driven lighting.
• Modest densities are sufficient to mitigate thermal quenching, improving phosphor stability and efficiency.
• The scattering properties of these composites are advantageous for uniform color rendering in reflection-based white lighting systems.