Unraveling the Excitation-Dependent Pathways: Competing Thermal Mechanisms of Ce 3+ Emission in LuAG Transparent Ceramics

Abstract

Ce-activated lutetium aluminum garnet (LuAG:Ce) polycrystalline transparent ceramics (PTCs) are promising materials for high-power lighting and radiation detection due to their excellent thermal stability and scintillation performance. Here, Variable-temperature photoluminescence of the prepared LuAG:Ce PTC was systematically investigated under blue and ultraviolet (UV) laser excitation. The results show that the thermal quenching behavior of its characteristic green emission strongly depends on the excitation energy. Under blue laser excitation, conventional thermal quenching occurs with increasing temperature. In contrast, UV excitation leads to a distinct negative thermal quenching effect. By developing a three-level system model, we found the distinct luminescence behaviors can be attributed to different pathways of photoexcited carriers, and the anomalous temperature-dependent luminescence behavior is arguably related to the thermal enhancement of the relaxation rate of photoexcited carriers from the 5d 2 level to the 5d 1 level of luminescent Ce 3+ ions. This study provides valuable insights into the excitation-dependent thermal quenching mechanisms, offering guidance for the design of LuAG-based optoelectronic devices with tailored thermal stability.