The self-activated LiGa5O8 storage phosphor: insights into its photo/thermo/mechano-stimulated NIR luminescence†

Abstract

Multi-mode storage phosphors with photo/thermo/mechano-stimulated luminescence (PSL/TSL/ML) hold great potential applications in many fields such as biological imaging, human–machine interface, robotic manipulation, and stress/temperature visualization sensing. However, the physical mechanisms underlying this ‘self-sustaining’ luminescence are still debated, which in turn hinders the development of materials. Here, we demonstrate that the intrinsic defects such as the oxygen atom vacancies () and interstitial oxygen atoms () in the matrix play an important role in the electronic structure and various physical properties of the LiGa₅O₈ storage phosphor by combining first-principles calculations and experimental methods. Particularly, the intrinsic defects lead to reduced bulk (B) and shear (G) moduli, Young's moduli (E), Poisson's ratio (v), B/G, and the bigger elastic anisotropy index (A^U) and hardness (H) in three LiGa₅O₈ defect models, which are extremely advantageous for PSL/TSL/ML. We also demonstrate that the ML process, different from PSL/TSL processes, is intimately linked to the activation threshold of charge carriers in traps. This threshold can be lowered under axial stress by bandgap narrowing. This study provides not only direct evidence for potential variations in the ML process but also guidance for designing storage phosphors via defect engineering.