Sm-doped SrBO was synthesized for high-sensitivity thermometry. A high thermal-sensitive fluorescence intensity ratio and fluorescence lifetime were achieved in a wide temperature range. At 500 K, the relative sensitivity of the temperature sensing was 2.16% K for the fluorescence intensity ratio and 3.36% K for the fluorescence lifetime. Furthermore, the fluorescence color-shifted dramatically from deep red at room temperature to green at 700 K. On the basis of this color change, a visible temperature field was obtained on quartz glass covered with our sample, which made the thermal conduction and distribution visible to the human eye. The temperature of the temperature field was determined using two methods. These outstanding properties, combined with the high sensitivity, multimode for temperature sensing and thermal stability of the sample, make SrBO:Sm a promising material for highly sensitive thermometry applications.

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A strategy of optical temperature sensing was developed by using various thermal quenching of Mn4+ and Eu3+ for double perovskite tellurite phosphor in optical thermometers. Herein, SrGdLiTeO6 (SGLT): Mn4+,Eu3+ phosphors were synthesized by a high-temperature solid-state reaction method. The temperature-dependent emission spectra indicated that two distinguishable emission peaks originated from Eu3+ and Mn4+ exhibited significantly diverse temperature responses. Therefore, optical thermometers with a dual-mode mechanism were designed by employing a fluorescence intensity ratio (FIR) of Mn4+ (2Eg→4A2g) and Eu3+ (5D0→7F1,2) and the decay lifetime of Mn4+ as the temperature readouts. The temperature sensing of the phosphors ranging from 300 to 550 K were studied. The maximum relative sensitivities (Sr) are obtained as 4.9% K−1 at 550 K. Meanwhile, the 695 nm emission of Mn4+ possessed a temperature-dependent decay lifetime with Sr of 0.229% K−1 at 573 K. Relevant results demonstrate the SrGdLiTeO6:Mn4+, Eu3+ phosphor as an optical thermometer candidate and also provide constructive suggestions and guidance for constructing high-sensitivity dual-mode optical thermometers.