Upconversion and Downconversion Luminescence of CaLaLiTeO6:Mn4+/Er3+ Phosphors for Dual-Mode Optical Thermometry and Anti-Counterfeiting Application

Multifunctional phosphors that integrate optical temperature measurement and counterfeit detection capabilities have garnered considerable interest owing to their diverse application potential. In this study, novel CaLaLiTeO6:Mn4+/Er3+ phosphors were prepared via the high-temperature solid-phase method. The phase structure and morphology characterization confirmed the successful synthesis of CaLaLiTeO6 material with effective doping of Mn4+ and Er3+ into the host lattice. Upon excitation at 379 nm, the CaLaLiTeO6:Mn4+/Er3+ material exhibits far-red emission at 716 nm (Mn4+:2Eg → 4A2g) and green emission at 525/548 nm (Er3+:2H11/2/4S3/2 → 4I15/2). The emission peak intensities of Er3+ and Mn4+ ions in the CaLaLiTeO6:0.015Mn4+/0.01Er3+ sample displayed distinct variations with temperature under different excitation wavelengths (325 nm, 379 nm, and 980 nm). Subsequently, a dual-mode optical temperature sensing system was developed based on the fluorescence intensity ratio and the dual excitation single-band ratiometric method, which achieved a maxed relative sensitivity of 1.12% K−1 at 343 K. Moreover, the excitation-dependent luminescence color changes of CaLaLiTeO6:Mn4+/Er3+ make it particularly suitable for anti-counterfeiting applications. The present study underscores the dual-functional capabilities in sophisticated non-contact optical temperature measurement and anti-counterfeiting applications.