A Sm3+-activated BaLaLiTeO6 double perovskite phosphor for multimode optical thermometry

Optical thermometry based on rare-earth-activated phosphors has attracted increasing interest for non-contact temperature sensing applications. Herein, a Sm 3+ -activated BaLaLiTeO 6 (BLLT:Sm 3+ ) phosphor is developed and systematically investigated as a multimode optical thermometric material. Benefiting from the thermally coupled 4 G 5/2 → 6 H J transitions of Sm 3+ ions, multiple fluorescence intensity ratio (FIR) thermometric modes are established, all exhibiting high fitting reliability and favorable sensitivities. Notably, a maximum relative sensitivity ( S R ) of 3.14% K −1 is achieved, demonstrating the effectiveness and flexibility of the multimode thermometric strategy. The optimal Sm 3+ concentration is determined to be 4 mol%, with concentration quenching governed by electric dipole–dipole interaction. In addition to its excellent thermometric performance, the phosphor exhibits intense orange-red emission with a high photoluminescence quantum yield (PLQY) of 39.02%, providing strong emission signals that are advantageous for reliable optical temperature sensing. These results highlight BLLT:Sm 3+ as a promising thermally robust phosphor for advanced optical temperature sensing.