Optical thermometry based on thermal population of low-lying levels of Eu3+ in Ca2.94Eu0.04Sc2Si3O12

Non-contact optical thermometry using rare-earth materials has attracted a lot of attention due to its realization of non-invasive and real-time temperature determination. In the current work, a new mechanism, differing from the conventional approach utilizing the ratio of intensities emitted from two thermally coupled excited levels, was developed and demonstrated for temperature sensing using Eu 3+ -doped Ca 3 Sc 2 Si 3 O 12 (CSSO). Under the excitation of 610.6 nm-wavelength light, Eu 3+ ions at the 7 F 2 multiplet became excited to the 5 D 0 state, and then the luminescence intensity originating from the 5 D 0 state increased significantly as the temperature was increased from 123 K to 273 K. The thermoequilibrium of the 7 F 2 multiplet with the 7 F 0 ground state at a weak excitation ensured a steady increase of the luminescence intensity I with temperature T , which well fit the equation I = A exp (− B / T ) for the transitions to both 7 F 1 and 7 F 4 multiplets. A relative sensitivity S R of 1008/ T 2 was obtained for the 7 F 1 case, with a value of 1.35% at 273 K. This scheme, as a result of detecting the blue-shifted emission, has the advantages of being less disturbed by stray light from the host and the object of the thermometry. In addition, the high quantum efficiency of a one-photon excited photoluminescence scheme has the advantage of improving the resolution of the thermometry. Furthermore, a near-infrared broadband emission observed in the sample can be adopted as a reference, so as to transform the scheme into one using a luminescence intensity ratio. These results indicated that CSSO:Eu 3+ may be used in practical temperature sensing applications. Non-contact optical thermometry using rare-earth materials has attracted a lot of attention due to its realization of non-invasive and real-time temperature determination.