The optical temperature sensing performance of Bi3+, Sm3+ co-doped CaWO4 phosphors

CaWO4 phosphors with fixed Bi3+ doping concentration and varied Sm3+ doping concentration have been prepared for this study. XRD analysis showed that the samples were scheelite in structure. The FE-SEM images revealed that the samples appeared to be the form of micrometer spheres. The results of the experiments analysed show that the luminescence of Bi3+ has a significant thermal quenching trend, while the tendency of the luminescence of Sm3+ to be thermally quenched is slower, resulting in an increase in the FIR of Sm3+ to Bi3+ with increasing temperature. Using this FIR to represent temperature gives a high relative sensitivity. The maximum relative sensitivity of the phosphor prepared in this experiment was 3.56 % K-1 (CaWO4: 5 mol% Bi3+, 0.1 mol% Sm3+, 303 K). As the temperature increases, we observe that the luminescence colour of CaWO4: Bi3+, Sm3+ changed. This makes it possible to be able to estimate the temperature change using the colour change. Temperature cycling tests showed that the FIR repeatability of the samples was very well. In conclusion, CaWO4: Bi3+, Sm3+ phosphors have promising applications in optical temperature sensing technology.