Temperature sensing based on the up-conversion emission of Tm3+ in a single KLuF4 microcrystal

Abstract The mono-dispersed hexagon microcrystal of KLuF 4 :24%Yb 3+ /0.5%Tm 3+ with an average particle size of 5 μm has been synthesized by a facile hydrothermal method. Based on the fluorescence intensity ratio (FIR) technique, the dependence of the up-conversion (UC) emission intensity of a single KLuF 4 :24%Yb 3+ /0.5%Tm 3+ particle on the ambient temperature ranging from 303 to 503 K has been studied in detail. The sensitivity of the 1 G 4 (a)/ 1 G 4 (b) and 3 F 2,3 / 3 H 4 thermally coupled levels (TCLs) is calculated, and the maximum sensitivity of which is 2.101 × 10 −3  K −1  at 303 K and 1.451 × 10 −4  K −1  at 503 K, respectively. Furthermore, the temperature of KLuF 4 :24%Yb 3+ /0.5%Tm 3+ single-particle rise from 347 to 366 K when the pump power increases from 168 to 1145 mW. It proves the heating effect of 3 F 2,3 / 3 H 4 TCLs is induced by 980 nm laser excitation. Compared with 1 G 4 (a)/ 1 G 4 (b) TCLs, the sensitivity of 3 F 2,3 / 3 H 4 TCLs exhibits better accuracy at high temperature. Moreover, the excellent thermal stability of the KLuF 4 :24%Yb 3+ /0.5%Tm 3+ microcrystal for temperature detection in the range of 303–503 K is proved. The Yb 3+ /Tm 3+ co-doped KLuF 4 single-particle shows promising applications in the fields of compact optical thermometers and optical heaters.