Highly Efficient and Thermally Stable Red‐Emitting Glass Ceramics by Induced Self‐Reduction for Laser Lighting

ABSTRACT Phosphor‐converted white laser diodes (pc‐wLDs) are evolving to achieve higher color rendering index (Ra), appropriate correlated color temperature (CCT), and higher power. However, challenges, including the absence of red spectral components and significant heat accumulation in converters, remain significant obstacles. In this work, an appealing red‐emitting Mg 2 Al 4 Si 5 O 18 :Eu (MASE) cordierite glass–ceramic (GCs) bulks are prepared for the first time under an air atmosphere, employing the glass crystallization method. Impressively, through optimizing the crystallization temperature and duration, the MASE GCs demonstrate remarkable thermal stability, maintaining 101% of their room temperature emission intensity even at 423 K and exhibiting high saturation thresholds exceeding 32.94 W/mm 2 , coupled with a high quantum yield (QY) of 75.1%. Meanwhile, the self‐reduction and crystallization mechanisms of MASE GCs are systematically investigated. Moreover, powered by a 7.77 W/mm 2 blue laser, the reflective white LDs device (LuAG:Ce/MASE composite device), encapsulated with stacked LuAG:Ce ceramics and MASE GCs, produced high‐quality warm white light with a high Ra of 92.9, a low CCT of 3370 K, and an exceptional QY of 84.7%. This work demonstrates that utilizing the self‐reduction reaction to prepare the high thermal stability red‐emitting phosphor material is an economical, efficient, and innovative approach, offering promising potential applications in next‐generation pc‐wLDs.