High Luminous Efficacy and Thermal Stability of LuAG:Ce Phosphor Ceramics with Porosity for High-brightness Laser Lighting

The generation of high-brightness white light in laser-illuminated devices is achieved by exciting yellow-green phosphors with a blue laser source. This configuration offers advantages such as high energy density and strong central luminous intensity. Among luminescent materials, LuAG:Ce phosphor ceramics (PCs) are notable for their high thermal stability and luminous output. In this study, LuAG:Ce PCs were produced from co-precipitated monophase nanopowders. The effects of vacuum sintering and air annealing temperatures on their porosity and luminescent properties were investigated. The sample, sintered at 1550°C and subsequently annealed at 1350°C, exhibited 3.5 vol.% porosity, highest room-temperature emission intensity in the series, and retained 96% of that intensity upon heating to 250°C. Under 450 nm laser-diode excitation, the sample achieved a luminous efficacy of 229 lm·W$^{-1}$ while maintaining excellent thermal stability. These results indicate that introducing controlled porosity to act as light-scattering centers in LuAG:Ce ceramics is a viable materials-design strategy for enhancing the luminous performance of laser-driven lighting devices.