Eu³⁺ doped CaWO₄ nanophosphor for high sensitivity optical thermometry

Eu³⁺ doped calcium tungstate phosphors were obtained by using sodium citrate as chelating agent in hydrothermal process. The structure and morphology of the samples were indicated by XRD and the FE-SEM. The samples prepared by us are scheelite structure. In addition, the particle size of sample decreases with sodium citrate dosage increasing, and finally reaches the nanoscale. The average particle size is 90 nm. The temperature measurement properties of phosphors were tested. It can be seen from test results that the thermal quenching behavior of Eu³⁺ and WO₄^2- luminescence has obvious difference. Hence, the FIR of Eu³⁺ and WO₄^2- can be used to express temperature. The maximum relative sensitivity increases with the decrease of particle size and the maximum is 4.3% K^-1 (303 K, 90 nm). Moreover, the color of sample luminescence altered continuously from blue to pink-red as the temperature increased. The luminous color of the sample can be used to roughly estimate the temperature. Therefore, the CaWO₄: Eu³⁺ nanophosphor are promising materials for optical thermometry.