Luminescence properties of Ba₄Yb₃F₁₇:Er³⁺ nanocrystals embedded in glass ceramics for optical thermometry

Transparent glass ceramics (GCs) containing Ba₄Yb₃F₁₇:Er³⁺ nanocrystals were successfully fabricated by a traditional melt-quenching method. The formation of Ba₄Yb₃F₁₇ nanocrystals was confirmed by X-ray diffraction, transmission electron microscopy, and selected area electron diffraction. Compared with the precursor glass, the enhanced emission intensity and lifetime of GCs indicate that the Er³⁺ ions incorporate into the Ba₄Yb₃F₁₇ nanocrystals after crystallization. The color tuning properties with doping under 980 nm excitation have been systematically discussed. It was found that the red/green ratio increased with Er³⁺ ion doping and the corresponding color changed from greenish-yellow to yellow-green. Furthermore, the temperature-dependent luminescence properties were studied in detail by the fluorescence intensity ratio (FIR) technique. The monotonic change of FIR with temperature indicates that this material is suitable for temperature sensing. At a temperature of 450 K, the relative sensitivity of the prepared sample reached its maximal value of 0.20% K^-1. The results show that the GCs containing Ba₄Yb₃F₁₇:Er³⁺ nanocrystals are candidate materials for temperature sensing.