Achieving\nNear-Infrared Highly Sensitive Temperature\nSensing in Lanthanide-Doped Lead-Free Double Perovskite NaLaMgWO<sub>6</sub> with Significant Thermal Enhancement

The significant temperature response of lanthanide-doped\nup-conversion\nluminescent materials is typically characterized by a severe thermal\nquenching of the luminescence intensity at elevated ambient temperatures,\nwhich severely restricts materials’ capability in temperature\nsensing. Herein, the influence of matrix phonon properties on the\nremarkable thermal enhancement effect in the thermosensitive material\nNaLaMgWO<sub>6</sub>:Yb<sup>3+</sup>/Nd<sup>3+</sup> is reported.\nIt is elucidated that achieving a significant thermal enhancement\nof Nd<sup>3+</sup> with a higher phonon energy oxide matrix is easier\nthan a halide matrix, which has lower phonon energy by comparison\nwith previous findings. Interestingly, the emission of thermally related\nlevels gets enhanced to various extents through phonon-assisted thermal\npopulation. In light of this, a three-model thermometer is constructed\nbased on luminescence intensity ratio (LIR) technology. Given that <i>S</i><sub>r</sub> and Δ<i>E</i> possess a positive\ncorrelation, it is feasible to acquire greater temperature monitoring\nsensitivity <i>S</i><sub>r</sub> in Nd<sup>3+</sup>, which\nhas a larger Δ<i>E</i>. At 313 K, this thermometry\nmodel may achieve a maximum sensitivity of 2.84%·K<sup>–1</sup>. This work not only provides guidance for the selection of efficient\nnear-infrared up-conversion material but also opens up a prospect\nfor the realization of ultrasensitive thermally coupled luminescent\nthermometers.