Temperature sensing materials based on the FIR of doped ions and the matrix in CaWO4:Sm3+phosphors

In this research, CaWO4:x mol% Sm3+ (x = 0.02, 0.1, 0.5) phosphors were prepared with the precipitation method. The temperature-dependent emission and excitation spectra of samples were measured. It could be found that in the Sm3+-doped CaWO4 phosphors, the luminescence intensity of the matrix decreased significantly with the increasing temperature in the range of 303-503 K, showing a normal thermal quenching trend, but the Sm3+ showed the phenomenon of thermal enhancement, and the luminescence intensity increased with the temperature increase. This phenomenon was the result of the enhanced energy transfer effect from WO42- to Sm3+ with the temperature increase. The fluorescence intensity ratio (FIR) of Sm3+ to the matrix increased monotonously with the temperature, which could achieve high-sensitivity thermometry. The CaWO4:0.5 mol% Sm3+ phosphor prepared in this research had a maximum relative sensitivity of 7.08 % K-1 (303 K). This was a relatively high value for an inorganic material. The good repeatability of the FIR measurements was confirmed with temperature cycling tests on the samples. In summary, CaWO4:Sm3+ is an optical temperature-sensing material with potential applications.