Tunable upconversion luminescence and optical temperature sensing based on non-thermal coupled levels of Lu3NbO7:Yb3+/Ho3+ phosphors

The color-tunable upconversion (UC) emission and optical temperature sensing based on non-thermal coupled levels (NTCL) were observed from the Yb3+/Ho3+ codoped Lu3NbO7 phosphors synthesized by the solid-state method. The phosphors are capable of generating color tunable UC luminescence from green (yellow) to yellow (green) with the increase of the Yb3+ (Ho3+) concentration. The tunable emission is due to the different energy back transfer processes from Ho3+ to Yb3+. The temperature sensing performances are investigated in the temperature range of 293-573 K based on NTCL by using fluorescence intensity ratio technology. The maximum absolute sensitivities are 0.37%K-1, 0.94%K-1, 0.27%K-1 at 298 K, which are based on three pairs NTCL of (F-5(4)/S-5(2)-> I-5(8))/(F-5(5)-> I-5(8)), (F-5(5)-> I-5(8))/(F-5(4)/S-5(2)-> I-5(7)) and (F-5(4)/S-5(2)-> I-5(8))/(F-5(4)/S-5(2)-> I-5(7)) of Ho3+, respectively. The above results suggest that the as-prepared Lu3NbO7:Yb3+/Ho3+ phosphors have great potential for the application prospects of upconverter, color tunable device and optical temperature sensor.