Temperature-responsive dual-emission Ba2ZnSi2O7 phosphors co-doped with Tb3+ and Dy3+ for optical thermometry applications

In this work, dual-emission phosphors based on Ba2ZnSi2O7 co-doped with Trivalent Terbium and Trivalent Dysprosium ions were successfully synthesized using a high-temperature solid-state method. X-ray diffraction analysis confirmed the monoclinic crystal structure with C2/c space group and phase purity of the materials, further validated by Rietveld refinement. Scanning electron microscopy revealed irregularly shaped nanoparticles in the nanometer range. Under UV excitation at room temperature, the phosphors exhibited characteristic green and yellow emissions attributed to Tb3+ and Dy3+, respectively. The optimal Dy3+ doping level was found to be 1.5 mol%, which also showed an increasing bandgap trend with higher Dy3+ concentrations. FTIR spectra confirmed no structural variation even after co-doping Dy3+ with Tb3+. TGA curves were analysed, and they were found to be stable after 200 °C with minimum loss of weight. Temperature-dependent photoluminescence studies indicated that Dy3+ emission underwent significant thermal quenching, with an activation energy of 0.152 eV and a quenching temperature of 382 K, making the material suitable for LED applications. The low phonon energy also revealed their suitability for producing optical thermometry sensors with materials. In contrast, the Tb3+ emission remained relatively stable with temperature variations. Temperature sensing capabilities were evaluated using fluorescence intensity ratio and lifetime-based methods, achieving maximum relative sensitivities of 4.96 % K−1 at 298 K and 1.64 % K−1 at 498 K, respectively. These findings highlight the potential of Tb3+/Dy3+ co-doped Ba2ZnSi2O7 phosphors as promising candidates for optical thermometry technologies.