Composite Al₂O₃-Ce:LuAG Phosphor Ceramics with High Luminous Efficacy and Thermal Conductivity for High-Brightness...

Despite the success of using Al₂O₃ as a secondary phase in Ce:LuAG phosphor ceramics (PCs), there is still room for improvement in the compositional design of biphasic PCs, as well as in their luminescent and thermal performance. In this study, nanopowders with 40 wt.% Al₂O₃-0.4at.% Ce:LuAG stoichiometry were synthesized via a co-precipitation approach. Subsequently, a series of compositionally uniform PCs was successfully fabricated by adjusting the vacuum sintering temperature and dwelling time. The grain size distributions of the Al₂O₃ and LuAG phases, as well as the evolution of porosity and pore size, were systematically analyzed and correlated with the sintering conditions. The addition of Al₂O₃ has been demonstrated to enhance the thermal properties of ceramics. The thermal conductivity of the "1750 °C × 10 h" sample was 15.6 W·m^-1·K^-1 at room temperature. Concurrently, it exhibited excellent thermal quenching behavior, retaining 96% of its luminescence intensity upon heating to 450 K. Its fluorescence lifetime was determined to be 21.06 ns. Under 450 nm laser excitation, the optimized PC attained a luminous efficacy of 286 lm·W^-1 at 1 W·mm^-2. In addition, the luminous flux increased continuously with laser power from 1 to 20 W·mm^-2 without any sign of saturation, reaching a maximum of 2500 lm. The findings indicate that biphasic 40 wt.% Al₂O₃-0.4at.% Ce:LuAG PCs have potential as high-flux, green-color converters for next-generation high-power laser lighting. Furthermore, a laser illumination prototype device incorporating 40 wt.% Al₂O₃-0.4at.% Ce:LuAG ceramic samples and a 10 W blue laser was constructed. This device emits white light with an illumination range exceeding 500 m, thereby demonstrating its potential applications in laser-driven lighting.