Optical temperature sensing properties of Tm3+/Yb3+ co-doped LuAG polycrystalline phosphor based on up-conversion luminescence

A series of LuAG: 5 mol%Yb3+/x mol%Tm3+ (x = 0.1, 0.3, 0.5, 1, 2) poly-crystals have been prepared through floating zone method with CO2 laser. The up-conversion luminescence spectra of the samples were recorded under 980 nm excitation. The results tell us that the optimal concentration of Tm3+ ions is around 0.3 mol%. Moreover, the optical temperature sensing properties of the LuAG: 5 mol%Yb3+/0.3 mol%Tm3+ have been investigated by using fluorescence intensity ratio (FIR) method. The FIR data obtained agree well with the fitting curve from 298 K to 1023 K. The absolute and relative sensitivities reach the highest values of 5.55 × 10−3 K−1 at 1023 K and 7.17 × 10−3 K−1 at 555 K, respectively. The results indicate that the Tm3+/Yb3+:LuAG poly-crystalline phosphor is a promising candidate for wide-range and highly sensitive temperature sensor.