MgF2-doped MgO-YAG:Ce composite ceramics prepared by pressureless vacuum sintering for laser-driven lighting

Abstract

Laser-driven solid-state lighting has attracted much attention in recent years. However, the super-high luminous flux under high-power-density laser irradiation is accompanied by an enormous amount of heat. Here, to enhance the thermal robustness of phosphor converter materials, we prepared composite ceramics of YAG:Ce combined with high-thermal-conductivity MgO via simply vacuum sintering. 1.0 mol% MgF2 was employed as the liquid-phase sintering additive to accelerate the densification process. The optimum temperature proves to be 1400 °C, at which MgO-YAG:Ce composites exhibit highly dense composite structure, without obvious reaction between MgO and YAG phases. Additionally, low sinterability of commercial YAG:Ce particles dragged down the densification process, which limits the YAG:Ce content of the composites. As a result, MgF2-doped MgO-10 vol% YAG:Ce composite ceramic (MYF10) sintered at 1400 °C exhibits the highest relative density of 99.33 % and thermal conductivity of 42.05 W/(m·K). Under 34.06 W/mm2 blue laser excitation in a reflection mode, a stable laser-driven white light is obtained with the luminous flux of 2834 lm and luminous efficiency of 166 lm/W, respectively.