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

The Er 3+ doped double perovskite Ba 2 CaWO 6 crystal is a promising ratiometric thermometer based on the fluorescence intensity ratio (FIR) of transitions from 2 H 11/2 and 4 S 3/2 to the lowered 4 I 15/2 level. However, the Ca 2+ 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 Er 3+ , Yb 3+ doped Ba 2 CaWO 6 are tuned by tri-doping with alkaline ions. The Ca 2+ vacancy defect can be eliminated by the introduction of Na + , which occupies the Ca 2+ site when it is doped into Ba 2 CaWO 6 with Er 3+ and Yb 3+ . On the contrary, the doping of Cs +  into Ba 2 CaWO 6 with Er 3+ and Yb 3+ enhances the defect concentration because it occupies the site of Ba 2+ . Thus, the tri-doping of Na + reduces the non-radiative probability and enhances the quantum efficiency of Er 3+ , leading to the improvement of the thermometric sensitivity of Ba 2 CaWO 6 . As a result, we get an excellent thermometric Ba 2 CaWO 6 :8%Yb 3+ ,3.5%Er 3+ ,6%Na + powder with a luminescence lifetime of 515 μs and maximum thermal sensitivity ( S r ) of 1.45%/K, which is more than three times higher than that of the BCWO:Er 3+ powder.