Optical thermometry based on up-conversion emission behavior of Ba2LaF7 nano-crystals embedded in glass matrix

Ba2LaF7:Yb3+, Er3+ nano-crystals embedded in a transparent aluminium silicate glass matrix was successfully fabricated by a traditional high temperature melt-quenching technique and the subsequently heat treatment process. The formation of Ba2LaF7 nano-crystals was confirmed by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The enhancement of the up-conversion (UC) emission intensity of Er3+ in the glass ceramic (GC) was attributed to the crystallization of Ba2LaF7 nano-crystals with a low phonon energy compared to the precursor glass counterpart. The temperature-depended fluorescence intensity ratio (FIR) of thermally coupled emitting states (4S3/2, 2H11/2) behavior of Er3+ was studied under the excitation of 980 nm. The maximum thermal sensitivity was approximately 0.43% K−1 at 298 K. Besides, the temperature of Ba2LaF7 GC rose from 336 to 407 K, when the laser pump power density increased from 1.01 to 9.59 W/cm2. Moreover, the excellent thermal stability of the sample for temperature detection in the range of 398-573 K was proved. The results indicate that the Yb3+/Er3+ co-doped Ba2LaF7 GCs could be potential candidates for integrating heaters and thermometers.