Improving luminescence and thermometric performance of Ba2CaWO6:Er3+ by tri-doping with Yb3+ and Na+

The Er3+ doped double perovskite Ba2CaWO6 crystal is a promising ratiometric thermometer based on the fluorescence intensity ratio (FIR) of transitions from 2H11/2 and 4S3/2 to the lowered 4I15/2 level. However, the Ca2+ vacancy defect caused by the charge difference between rare-earth ions and the substituted alkaline-earth ions gives rise to the non-radiative probability and limits the thermal sensitivity. Here, the up-conversion luminescence and thermometric performance of Er3+, Yb3+ doped Ba2CaWO6 are tuned by tri-doping with alkaline ions. The Ca2+ vacancy defect can be eliminated by the introduction of Na+, which occupies the Ca2+ site when it is doped into Ba2CaWO6 with Er3+ and Yb3+. On the contrary, the doping of Cs+ into Ba2CaWO6 with Er3+ and Yb3+ enhances the defect concentration because it occupies the site of Ba2+. Thus, the tri-doping of Na+ reduces the non-radiative probability and enhances the quantum efficiency of Er3+, leading to the improvement of the thermometric sensitivity of Ba2CaWO6. As a result, we get an excellent thermometric Ba2CaWO6:8%Yb3+,3.5%Er3+,6%Na+ powder with a luminescence lifetime of 515 μs and maximum thermal sensitivity (Sr) of 1.45%/K, which is more than three times higher than that of the BCWO:Er3+ powder.