Luminescence properties of a green-emitting mechanoluminescent phosphor CaSrGa 4 O 8 : x Tb 3+ without pre-excitation.

In this study, both mechanoluminescence (ML) and long persistent luminescence (LPL) characteristics were first observed in CaSrGa 4 O 8 doped with Tb 3+ ions, which confirmed that CaSrGa 4 O 8 is a high-quality host for luminescent material research. Notably, the samples show stronger mechanoluminescent intensity with increasing Tb 3+ doping. Additionally, the introduction of Tb 3+ led to a shift of the thermoluminescence peak towards higher temperatures and a substantial increase in its intensity, suggesting that Tb 3+ doping enhances the overall trap concentration and introduces deeper trap energy levels. Presumably, the free carriers in the system recombine upon mechanical stimulation, releasing energy that is transferred to Tb 3+ ions. Investigations into the intrinsic structure, matrix effects, and trap evolution of the material confirmed that deep and shallow traps are responsible for the observed ML and LPL phenomena, respectively. The elucidation of the unique luminescent properties of the material provides us with some guidance for the development of new multi-functional luminescent materials.