A new optical temperature sensor based on the fluorescence intensity ratio of Mn2+ and Mn4+

Abstract In the course of preparing Mn‐doped phosphors, the mix‐valence state of Mn n + ions may be obtained with associated interesting properties. This work prepared a new phosphor Ba 3 MgSb 2 O 9 :Mn (BMS:Mn) by a traditional high‐temperature solid‐state synthesis method. In this structure, Mn n + can replace Mg 2+ site as Mn 2+ oxidation state or Sb 5+ site as Mn 4+ . Moreover, the emitting bands of Mn 2+ and Mn 4+ at around 596 and 758 nm are simultaneously observed by using 350 nm as exciting wavelength. Interestingly, the temperature‐dependent emitting intensities corresponding to Mn 2+ and Mn 4+ are different at temperatures from 10 to 300 K. With increasing temperature, the intensity of Mn 2+ luminescence has some enhancement at 10–200 K and then decreases gradually, whereas Mn 4+ luminescence goes into rapid decline. By using this character, BMS:0.01Mn can be used as an optical temperature sensor at 10–300 K based on the fluorescence intensity ratio of Mn 2+ and Mn 4+ . The maximum relative sensitivity ( S r ) at 125 K is as high as 1.51% K −1 .