Tuning self-recoverable mechanical-to-optical energy conversion of MgO-based smart simple oxides

Mechanoluminescence (ML), which refers to the light emission in response to mechanical stimuli, presents significant potential for stress sensing, anti-counterfeiting measures, and structural health monitoring. Currently, most ML materials are typically based on complex compositions or multiphase systems. In this study, we present that simple magnesium oxide (MgO) serves as an excellent host for producing self-recoverable near-infrared ML through doping Cr 3+ ions. We found that high sintering temperature significantly enhanced the ML intensity of MgO:Cr 3+ , which is ascribed to high equilibrium concentrations of charge carriers and defects, as confirmed by DFT calculations. The ML properties were further improved by rational optimization of dopant concentration, annealing atmosphere, Ln 3+ co-doping, and Zn 2+ /Al 3+ alloying. Additionally, the nanoplate-like MgO:Cr 3+ , which exhibits exceptional ML film-forming capabilities, was further synthesized using a molten-salt-assisted liquid-phase technique for the first time. Finally, proof-of-concept demonstrations confirmed its versatile capabilities in stress visualization, underwater communication, and surface damage mapping. Therefore, this research establishes MgO:Cr 3+ as a simple and efficient ML platform for multifunctional applications. • High-temperature sintering significantly enhances the self-recoverablemechanical-to-optical energy conversion intensity of the simple oxide MgO:Cr 3+ . • The highly efficient mechanoluminescence of MgO:Cr 3+ is attributed to the increased concentrations of defects and carriers, which is validated by DFT calculations. • Nanoplate-like mechanoluminescent MgO:Cr 3+ synthesized through a novel molten-salt-assisted method demonstrates excellent film-forming and adhesion properties. • Proof-of-concept applications of MgO:Cr 3+ -based smart materials demonstrate versatile uses in the advanced optoelectronic area, such as stress visualization, underwater communication, and surface damage mapping.