Dual-Mode Optical Thermometry Design in Lu₃Al₅O₁₂:Ce³⁺/Mn⁴⁺ Phosphor

There is a challenge for noncontact temperature-sensing techniques and the related materials, in which a highly reliable contactless thermometer probe with low cost and high sensitivity is in demand. Here, the Lu3Al5O12:Ce3+/Mn4+ phosphor has been designed and prepared for the high-performance fluorescence temperature-sensing application in a novel one-pot, self-redox, solid-state process. Benefiting from the different electron-lattice/phonon interactions of Ce3+ and Mn4+, two distinguishable emission peaks with significantly different temperature responses originating from Ce3+ and Mn4+ are realized. Applying the fluorescence intensity ratio of Mn4+ versus Ce3+ and the decay lifetime of Mn4+ emission as the temperature readout, a dual-mode optical temperature-sensing mechanism was proposed and studied in the temperature range of 100-350 K. The maximum relative sensitivities (Sr) are derived as 4.37 and 3.22% K-1 respectively, as well as a large chromaticity shift visible to naked eyes (ΔE = 153 × 10-3 in 100-350 K) is observed. This is the first report of a Ce3+,Mn4+ co-doped dual-emitting phosphor, and its unique optical thermometric features demonstrate the high potential of Lu3Al5O12:Ce3+/Mn4+ as an accurate and reliable thermometer probe candidate.