Optical thermometry based on up-conversion luminescence behavior in BaGdF5:Er3+ glass ceramics

Abstract

Er3+ ions are often used as up-conversion (UC) activators for fluorescence intensity ratio (FIR) thermometer technique, and Yb3+ ions are co-doped for improving the UC luminescence efficiency of Er3+ ions. However, Yb3+ ions will cause heating effect by absorbing 980 nm laser excitation which affects the precision of FIR technique. Challenge of FIR technique still remains to seek for superior host materials of high UC luminescence efficiency without sensitizer Yb3+ ions, in which heating effect can be reduced. Herein, glass ceramics (GC) containing Er3+-doped BaGdF5 nano-crystals (NCs) were successfully elaborated through melt-quenching method. X-ray diffraction, scanning transmission electron microscopy and element mappings are convinced the formation of BaGdF5 NCs. The UC emissions of Er3+ ions are greatly enhanced due to the Er3+ dopants incorporated into the BaGdF5 NCs with low phonon energy. The temperature dependent FIR of two thermal coupled energy levels (2H11/2/4S3/2) was carried out from 300 to 720 K, and the maximum relative sensitivity is 1.36% K−1 at 300 K. According to all the above results, the BaGdF5:Er3+ GC may have possible utilization in thermometer with high precision.