Temperature sensing behaviors of Er3+ and Pr3+ co-doped scheelite SrMoO4 phosphors

Optical thermometry based on fluorescence integral intensity ratio attracted more attention due to its advantages. Here, Er3+/Pr3+ co-doped scheelite SrMoO4 phosphors were successfully synthesized by normal high temperature solid method to explore their potential application in optical thermometer field. The dopants of Er3+ and Pr3+ had no effect on the structure of SrMoO4. The optimal total concentration of Er3+ and Pr3+ was observed at 1 mol%. The changes of emission intensity and the average lifetime of Er3+ with the varied concentration of Pr3+ suggested an energy transfer process from Er3+ to Pr3+ with the highest efficiency of 23 %. According to the temperature dependence of downconversion photoluminescence, the higher temperature sensitivity of 0.73 % K-1 was achieved based on the intensity ratio between the emissions assigned to H-2(11/2) -> I-4(15/2) transition of Er3+ and P-3(0) -> F-3(2) transition of Pr3+. Under the excitation wavelength of 980 nm, the upconversion emissions of Pr3+ was too tiny to be used for temperature characterization due to its low absorption cross section. Based on the fluorescence intensity ratio between the emissions attributed to thermal coupled levels of H-2(11/2) -> I-4(13/2) and S-4(3/2) -> H-4(15/2) transitions assigned to Er3+, the highest temperature relative sensitivity of 1.07 % K-1 was achieved, suggesting its potential application in optical thermometers.