A spatial/temporal dual-mode optical thermometry based on double-sites dependent luminescence of Li4SrCa(SiO4)2: Eu2+ phosphors with highly sensitive luminescent thermometer

Increasing demand for non-contact temperature sensing, in this paper, Li4SrCa(SiO4)(2) (LSCS) phosphor doped with Eu2+ was prepared, and the temperature dependence of its optical properties was studied in detail. The conformation of Eu2+ double-sites in LSCS host has been veritied by X-ray diffraction (XRD) spectrum, photo-luminescence spectra and decay curves. The temperature dependence of emission intensity and decay lifetime of Eu2+ in the range of 303 K-473 K has been studied systematically. Under the excitation of ultraviolet light (at 363 nm), the color of LSCS: xEu(2+) (x = 0.05) phosphor gradually changed from blue-violet (at 303 K) to light yellow (at 473 K) with the increase of temperature. The highest absolute sensitivity (Sa) of the material is 0.051 K-1 (at 473 K) and the relative sensitivity (Sr) is 3.18% K-1 (at 423 K) under fluorescence intensity ratio (FIR) detection technology. In addition, the temperature resolution ranges from 0.17 to 0.35 K. Based on fluorescence lifetime thermometry, the maximum of Sa is 1.47 K-1 (at 363 K) and Sr is 15.0% K-1 (at 573 K), obviously superior to the previously reported inorganic optical thermometry materials. Moreover, LSCS: Eu2+ has good signal recognition ability because of the different response of the two emission centers to temperature. Therefore, we believe that LSCS: Eu2+ has a good application prospect in the field of spatial/temporal optical temperature measurement.