Constructing ultra-sensitive dual-mode optical thermometers: Utilizing FIR of Mn4+/Eu3+ and lifetime of Mn4+ based on double perovskite tellurite phosphor

A strategy of optical temperature sensing was developed by using various thermal quenching of Mn 4+ and Eu 3+ for double perovskite tellurite phosphor in optical thermometers. Herein, SrGdLiTeO 6 (SGLT): Mn 4+ ,Eu 3+ phosphors were synthesized by a high-temperature solid-state reaction method. The temperature-dependent emission spectra indicated that two distinguishable emission peaks originated from Eu 3+ and Mn 4+ exhibited significantly diverse temperature responses. Therefore, optical thermometers with a dual-mode mechanism were designed by employing a fluorescence intensity ratio (FIR) of Mn 4+ ( 2 E g → 4 A 2g ) and Eu 3+ ( 5 D 0 → 7 F 1,2 ) and the decay lifetime of Mn 4+ as the temperature readouts. The temperature sensing of the phosphors ranging from 300 to 550 K were studied. The maximum relative sensitivities (S r ) are obtained as 4.9% K −1 at 550 K. Meanwhile, the 695 nm emission of Mn 4+ possessed a temperature-dependent decay lifetime with S r of 0.229% K −1 at 573 K. Relevant results demonstrate the SrGdLiTeO 6 :Mn 4+ , Eu 3+ phosphor as an optical thermometer candidate and also provide constructive suggestions and guidance for constructing high-sensitivity dual-mode optical thermometers.