High-sensitivity and wide-temperature-range dual-mode optical thermometry under dual-wavelength excitation in a novel double perovskite tellurate oxide.

Novel double perovskite SrLaLiTeO6 (abbreviated as SLLT):Mn4+,Dy3+ phosphors synthesized using a solid-state reaction strategy exhibit distinct dual-emission of Mn4+ and Dy3+. High-sensitivity and wide-temperature-range dual-mode optical thermometry was exploited taking advantage of the diverse thermal quenching between Mn4+ and Dy3+ and the decay lifetime of Mn4+. The thermometric properties in the range of 298–673 K were investigated by utilizing the fluorescence intensity ratio (FIR) of Dy3+ (4F9/2 → 6H13/2)/Mn4+ (2Eg → 4A2g) and the Mn4+ (2Eg → 4A2g) lifetime under 351 nm and 453 nm excitation, respectively. The maximum relative sensitivities (SR) of the resultant SLLT:1.2%Mn4+,7%Dy3+ phosphor under 351 nm and 453 nm excitation employing the FIR technology were determined to be 1.60% K−1 at 673 K and 1.44% K−1 at 673 K, respectively. Additionally, the maximum SR values based on the lifetime-mode were 1.59% K−1 at 673 K and 2.18% K−1 at 673 K, respectively. It is noteworthy that the SR values can be manipulated by different excitation wavelengths and multi-modal optical thermometry. These results suggest that the SLLT:Mn4+,Dy3+ phosphor has prospective potential in optical thermometry and provide conducive guidance for designing high-sensitivity multi-modal optical thermometers.