Achieving Near-Infrared Highly Sensitive Temperature Sensing in Lanthanide-Doped Lead-Free Double Perovskite NaLaMgWO₆ with Significant Thermal Enhancement

The significant temperature response of lanthanide-doped up-conversion luminescent materials is typically characterized by a severe thermal quenching of the luminescence intensity at elevated ambient temperatures, which severely restricts materials' capability in temperature sensing. Herein, the influence of matrix phonon properties on the remarkable thermal enhancement effect in the thermosensitive material NaLaMgWO₆:Yb³⁺/Nd³⁺ is reported. It is elucidated that achieving a significant thermal enhancement of Nd³⁺ with a higher phonon energy oxide matrix is easier than a halide matrix, which has lower phonon energy by comparison with previous findings. Interestingly, the emission of thermally related levels gets enhanced to various extents through phonon-assisted thermal population. In light of this, a three-model thermometer is constructed based on luminescence intensity ratio (LIR) technology. Given that <i>S</i>_r and Δ<i>E</i> possess a positive correlation, it is feasible to acquire greater temperature monitoring sensitivity <i>S</i>_r in Nd³⁺, which has a larger Δ<i>E</i>. At 313 K, this thermometry model may achieve a maximum sensitivity of 2.84%·K^-1. This work not only provides guidance for the selection of efficient near-infrared up-conversion material but also opens up a prospect for the realization of ultrasensitive thermally coupled luminescent thermometers.