Down-conversion based Tm3+:LiY1-XYbXF4 temperature sensors

Abstract

Single crystals of Tm3+ (0.2 at.%):LiY1-XYbXF4 (X = 0.2, 0.4, 0.6, 0.8, 1.0) phosphors were grown in the resistive furnace by the Bridgman-Stockbarger method. The obtained samples have a tetragonal structure. The samples were excited by λex = 688 nm pulse laser irradiation (3H6 – 3F2,3 absorption band of Tm3+). The presence of Yb3+ emission under excitation of Tm3+ ions indicates energy transfer from Tm3+ to Yb3+. It was suggested, that in the studied system, there is only the phonon-assisted energy transfer from 3H4 (Tm3+) to 2F5/2 (Yb3+). The luminescence intensity ratio (LIR) of Tm3+ (3H4 – 3H6) and Yb3+ (2F5/2 – 2F7/2) lead to absolute temperature sensitivity values of 0.0025–0.0035 K-1.The short-lived decay time increases with the temperature increase. The maximum Sr value obtained from short-lived decay time dependence on temperature is equal to 0.36%·K−1.In the frames of the present work, we developed a model allowing determining the probability values of energy transfer between Tm3+ and Yb3+ ions in the heavily-doped samples. The model takes into consideration multiphonon nature of interaction between the doping ions.