Upconversion of SrWO4:Er3+/Yb3+: Improvement by Yb3+ codoping and temperature sensitivity for optical temperature sensors

SrWO 4 :Er 3+ /Yb 3+ phosphors are synthesized by a solid state reaction . The XRD patterns indicate that the doping ions will not change the phase of SrWO 4 . Under the excitation at 980   nm, SrWO 4 :Er 3+ /Yb 3+ phosphors show emission bands in green and red regions. The temperature-dependence of upconversion efficiency and temperature-sensing properties of SrWO 4 :Er 3+ /Yb 3+ phosphors have been discussed according to the fluorescence intensity ratio of green emissions from 2 H 11/2 / 4 S 3/2   →   4 I 15/2 transitions of Er 3+ in the range of 95–775   K under the excitation at 980   nm. The maximum sensitivity of SrWO 4 :1%Er 3+ /6%Yb 3+ phosphor is found to be 0.01282   K −1 at 489   K.