Trap-regulated highly efficient mechanoluminescence and persistent mechanoluminescence of Ca2MgSi2O7:Eu2+

Abstract

Mechanoluminescent materials have shown promising applications in visualized mechanical sensing, imaging, and real-time monitoring because of unique mechanics-optics conversion. However, most mechanoluminescent materials exhibit weak intensity and transient emitting behavior, which severely hinders practical applications. In this work, trap-controlled mechanoluminescence (ML) under friction or compression was demonstrated in Ca₂MgSi₂O₇:Eu²⁺ when composited with epoxy resin. In addition to green-emitting ML with relatively good cyclic stability, Ca₂MgSi₂O₇:Eu²⁺ exhibited attractive persistent mechanoluminescence (Pers-ML) behavior (i.e., the sample could emit light continuously after removing the applied mechanical stimulus). This is a significant finding to break the restrictions caused by conventional transient ML behavior. By investigating the intrinsic structure, matrix effects and trap evolution, the “deep” traps and “shallow” traps were found to be responsible for the as-observed ML and Pers-ML, respectively. Based on the physical understanding stated above, a trap-regulating strategy by co-doping with Ho³⁺ was developed, which simultaneously enhanced ML and Pers-ML. These developed materials with highly efficient ML and Pers-ML could be promising for mechanics-driven lighting, displaying, imaging, and sensing applications in various fields.