Improvement in mechanoluminescence performance and implementation of dual-mode photoluminescence based on Bi3+ ion non-intrinsic defect control strategy

Abstract

The gallate salts are frequently employed as matrix for mechanoluminescence (ML) materials largely due to their plentiful defect energy levels and robust piezoelectric characteristics. Nevertheless, the ML performance of specific gallate materials is inferior to that of sulfides and fluorides and thus requires improvement. To address this issue, it is essential to engineer appropriate lattice defects in order to facilitate the advancement of new elastic ML materials. Therefore, in the present study, a series of Ca₃Ga₄O₉:0.01Bi³⁺,xTb³⁺ (x = 0.01, 0.02, 0.03, 0.04, 0.05 and 0.06) was synthesized using the traditional high-temperature solid-state method. Furthermore, a non-intrinsic defect control strategy utilising Bi³⁺ ions is presented, which serves to enhance the performance of calcium gallate. The ML intensity is enhanced by 112% in comparison to the undoped samples (concentration of Tb³⁺ is 0.04), resulting in an improved linearity between mechanical loading and ML intensity, along with the achievement of dual-mode photoluminescence (PL). By analysing the crystal structure, PL, ML, and thermoluminescence (TL) properties of Ca₃Ga₄O₉:Bi³⁺,Tb³⁺ (CGO:Bi³⁺,Tb³⁺), coupled with the first principles calculations using density functional theory (DFT), the ML mechanism of CGO:Bi³⁺,Tb³⁺ was elucidated. This leads to the development of a versatile anti-counterfeiting device with both flexible and rigid multi-mode capabilities.