Negative thermal expansion Sc₂W₃O₁₂: Pr³⁺ phosphor for multi-functional applications of optical thermometry,...

The thermal quenching of luminescent materials is a major obstacle to the applications of phosphors, and achieving anti-thermal luminescence remains challenging. In this work, negative thermal expansion (NTE) Sc₂W₃O₁₂: xPr³⁺ phosphors (x = 0.001-0.050) were prepared via a solid-state synthesis route. The Sc₂W₃O₁₂: xPr³⁺ phosphors exhibit dual excitation sources and dual emission colors: under 265 nm and 346 nm excitation, the phosphors produce red emission peaked at 611 nm and broad band blue emission centered at 426 nm, respectively. Remarkably, at a temperature of 373 K, the luminescence intensity of the as-prepared phosphor is approximately 700 % of that at room temperature for 611 nm emission. The enhanced luminescence at elevated temperature stems from the promoted energy transfer, which is induced by lattice contraction resulting from the negative thermal expansion property of the host material. Temperature-dependent lifetime confirmed the efficient energy transfer from [WO₄]^2- groups to Pr³⁺ ions, with an energy transfer efficiency of 88 % at 373 K. Leveraging the self-luminescent properties of [WO₄]^2- groups, an optical thermometry based on the fluorescence intensity ratio (FIR) of [WO₄]^2- emission to Pr³⁺ emission was established, yielding a relative sensitivity (S_r) of 1.89 % K^-1. The synthesized phosphor demonstrates anti-counterfeiting capabilities under different excitation wavelengths, and a color-switching system was designed to intuitively and clearly reveal encrypted information. These results indicate that Pr³⁺-doped Sc₂W₃O₁₂ phosphors hold potential for applications in optical thermometry, anti-counterfeiting and information encryption technologies.