Color-tunable upconversion photoluminescence and highly performed optical temperature sensing in Er³⁺/Yb³⁺ co-doped ZnWO₄.

Er³⁺/Yb³⁺ co-doped ZnWO₄ phosphors were synthesized by a solid state reaction method and their structure, photoluminescence and temperature sensing properties were characterized. The color-tunable upconversion emissions (from green to red) were observed by increasing the doped Er³⁺/Yb³⁺ concentration. The temperature sensing properties were studied by using the fluorescence intensity ratio technique in the temperature range of 83-583 K, and high performance was obtained. The maximum sensitivity is found to be 0.0099 K^-1 at 583 K. The XRD Rietveld refinement revealed that the phosphors crystallized in monoclinic structure with the space group P2/c (13) at room temperature. The results suggest that the phosphors could be an exceptional choice for next generation luminescence-based temperature sensing devices as well as in multiple biolabels.