A dual-mode optical thermometric strategy based on a Dy3+-activated tellurate double perovskite phosphor

Developing down-conversion phosphors with stable luminescence and high temperature sensitivity is essential for non-contact optical thermometry. Herein, a Dy 3+ -activated SrGdLiTeO 6 (SGLT:Dy 3+ ) phosphor was synthesized via a conventional solid-state reaction. Rietveld refinement confirms the phase-pure monoclinic double perovskite structure, revealing that Dy 3+ ions preferentially occupy the Gd 3+ sites. Upon near-UV excitation, the phosphor exhibits distinct blue ( 4 F 9/2  →  6 H 15/2 ) and yellow ( 4 F 9/2  →  6 H 13/2 ) emissions with tunable intensity and stable emission color as a function of dopant concentration. Notably, the anomalous enhancement of the 458 nm band with temperature enables the construction of two fluorescence intensity ratio (FIR) modes, yielding maximum relative sensitivities of 2.75% K −1 and 2.87% K −1 , respectively. Moreover, the phosphor maintains over 70% of its room-temperature emission intensity at 500 K, indicating robust thermal stability. This work offers a practical approach for developing Dy 3+ -activated phosphors with reliable optical thermometry performance and potential applicability in non-contact temperature sensing devices.