Dual-mode optical temperature sensing using Dy³⁺/Sm³⁺ co-activated Ba₂ZnSi₂O₇ phosphor with tuneable sensitivity

This study reports the synthesis and characterization of a novel Ba₂ZnSi₂O₇:Dy³⁺, Sm³⁺ phosphor designed for optical temperature sensing applications. The material was successfully prepared using a high-temperature solid-state reaction method. X-ray diffraction (XRD) confirmed a monoclinic crystal structure with high phase purity. Photoluminescence (PL) spectroscopy identified 1 mol% Sm³⁺ as the optimal doping concentration for efficient luminescence, and significant energy transfer from Dy³⁺ to Sm³⁺ was observed and quantified. Diffuse reflectance spectroscopy (DRS) indicated a widened bandgap due to a shift in the conduction band upon co-doping. Scanning electron microscopy (SEM) revealed an agglomerated morphology, while FTIR analysis confirmed the structural integrity of the host lattice after doping. Under 403 nm excitation, the activation energy for thermal quenching of Sm³⁺ emission was determined to be 0.19 eV. The fluorescence intensity ratio (I _Dy/I _Sm) displayed strong temperature dependence between 303 K and 483 K, achieving a maximum relative sensitivity of 7.19% K^-1 at 403 K. Additionally, Sm³⁺ lifetime measurements showed a high temperature-dependent sensitivity, with a maximum of 1.10% K^-1 at 303 K. These results highlight the material's excellent potential for high-performance optical temperature sensing.