Color-tunable upconversion luminescence and temperature sensing behavior of Tm3+/Yb3+ codoped Y2Ti2O7 phosphors

Tm3+/Yb3+: Y2Ti2O7 phosphors with color-tunable upconversion (UC) luminescence and optical thermometric property were synthesized and characterized. The phosphors exhibit intense blue and red UC emission bands under 980 nrn excitation. The blue to red emission intensity ratio shows an enhancement with increasing excitation power. Hence, the UC color can be tuned from almost white to blue by control of the excitation power density. The temperature sensing behaviors are studied based on fluorescence intensity ratio (FIR) technique at different excitation powers. FIR-1 from the thermally coupled levels ((1)G(4(a)) and (I)G(4(b))) is insensitive to the excitation power, which can obtain consistent measurement results at different excitation powers. Meanwhile, the utilization of FIR-2 from non-thermally coupled levels (F-3(2,3) and (1)G(4(b))) can achieve higher sensing sensitivities with the maximal value of similar to 0.81%K-1 at 398 K. Hence, Tm3+/Yb3+;Y2Ti2O7 phosphor has promising application prospects in the fields of upconverter, optical thermometer and color tunable device.