Investigation on the upconversion luminescence and ratiometric thermal sensing of SrWO4:Yb3+/RE3+ (RE = Ho/Er) phosphors

SrWO4 phosphors doped with Ho3+(Er3+)/Yb3+ are successfully prepared by a high temperature solid-state reaction method. The upconversion (UC) luminescence properties of all the samples have been investigated under 980 nm excitation. Strong green emissions are obtained in the SrWO4:Yb3+/Ho3+ and SrWO4:Yb3+/Er3+ samples with the naked eyes. In a temperature range going from 303 K to 573 K, the UC emission spectra of the phosphors have been measured. Then the temperature sensing properties also have been discussed via fluorescence intensity ratio (FIR) technology. For the SrWO4:Yb3+/Ho3+ phosphor, the FIR technologies based on thermal coupling levels (TCLs)(F-5(4),F-5(5)) and non-thermal coupling levels (non-TCLs)(S-5(2), F-5(4)/F-5(5)) are used for investigating the sensitivity. The results show that the maximum absolute sensitivity reaches 0.0158 K-1 with non-TCLs. As for Yb3+/Er3+ codoped SrWO4 phosphor, the maximum absolute sensitivity reaches 0.013 K-1 with TCLs (H-2(11/2),S-4(5/2)) at a temperature of 513 K. These significant results demonstrate that the SrWO4:Ho3+(Er3+)/Yb3+ phosphors are robust for optical temperature sensors.

Automated summary

SrWO4 phosphors doped with Ho3+(Er3+)/Yb3+ were successfully prepared by a high temperature solid-state reaction method, showing strong green emissions under 980 nm excitation. The upconversion luminescence properties were studied at different temperatures, and the temperature sensing properties were discussed using fluorescence intensity ratio technology. The results demonstrate that these phosphors are robust for optical temperature sensors, achieving maximum absolute sensitivity of 0.0158 K-1 and 0.013 K-1 for different dopants.