Effective long-term storage and repeatable mechanoluminescence of piezoelectrics LiNbO₃:1%Pr³⁺, 0.5%Zn²⁺

In this study, we investigated a novel multifunctional piezoelectric phosphor LiNbO₃:1%Pr³⁺, 0.5%Zn²⁺, which exhibited outstanding mechanoluminescence (ML) characteristics due to the strategic incorporation of Zn²⁺. A dual-regulation mechanism is proposed by adjusting the charge transfer band (CTB) energy level position and optimizing the defect distribution, thus realizing high-brightness, long-term storage, and highly repeatable red emission in ML. The addition of Zn²⁺ can lower the CTB energy level of the phosphor, which leads to the easier transfer of ³P₀ electrons of Pr³⁺ to the ¹D₂ energy level through the CTB band, thus enhancing the ML red emission. The introduction of a small amount of Zn²⁺ effectively couple the trap structure with the piezoelectric properties of the material, significantly enhancing ML properties. Notably, the material exhibits excellent ML repeatability and long-term storage, maintaining a strong ML response even after 30 d. Density functional theory calculations of the phosphor confirmed that the doping of Zn²⁺ in LiNbO₃:1%Pr³⁺ optimized the trap concentration and distribution, thereby improving the ML performance. This multifunctional material holds great potential for use in electromechanical and optoelectronic devices, contributing to the development of smart devices with broader applications.