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 Lu 3 Al 5 O 12:Ce 3+ /Mn 4+ 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 Ce 3+ and Mn 4+, two distinguishable emission peaks with significantly different temperature responses originating from Ce 3+ and Mn 4+ are realized. Applying the fluorescence intensity ratio of Mn 4+ versus Ce 3+ and the decay lifetime of Mn 4+ 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 ( S r ) are derived as 4.37 and 3.22% K –1 respectively, as well as a large chromaticity shift visible to naked eyes (Δ E = 153 × 10 –3 in 100–350 K) is observed. This is the first report of a Ce 3+,Mn 4+ co-doped dual-emitting phosphor, and its unique optical thermometric features demonstrate the high potential of Lu 3 Al 5 O 12:Ce 3+ /Mn 4+ as an accurate and reliable thermometer probe candidate.