A highly sensitive ratiometric optical thermometer based on Sr2MgWO6 double perovskite doped with Dy3+ exploiting thermally coupled and uncoupled levels

The increasing demand for highly sensitive optical thermometers operating within a wide temperature range necessitates the development of new phosphors. In this work, the potential of temperature sensing performance of a novel yellow-emitting phosphor, Sr2MgWO6 double perovskite, doped with varying concentrations of Dy3+ was investigated for the first time. Increasing the concentration of Dy3+ from 0% to 7% shifted the color of luminescence from blue to yellowish-orange within the CIE1931 color space. The energy transfer efficiency from (WO6)6- to Dy3+ also increased significantly to 98.4%. Moreover, the sample doped with 3% Dy3+ showed the highest emission intensity, with concentration beyond this threshold inducing concentration quenching. This phenomenon was primarily governed by dipole-dipole interactions. The highest quantum yield was found to be 30.7% for the sample doped with 3%Dy3+. Upon 266 nm excitation wavelength, the temperature sensing ability of the samples doped with 3%, 5%, and 7%Dy3+ was examined based on the fluorescent intensity ratio between thermally coupled and uncoupled levels. It showed that the relative thermal sensitivity of Sr can be tuned by changing the Dy3+ concentration. Sr-max = 3.24%K-1 was obtained for the sample doped with 3%Dy3+ at 193 K within the 80 - 273 K operating range for thermally uncoupled levels. For thermally coupled levels, the Sr-max value reached 1.35%K-1 at 333 K for the sample doped with 7%Dy3+ in the range of 293 – 593 K. These results demonstrated the enormous potential of the studied materials for thermal sensing application.