Fig. 1. XRD patterns of PG and GC samples, and the reference data of orthorhombic KYb₂F₇

Fig. 2. Transmittance spectra of PG and GC samples

Fig. 3. Fluorescence spectra of PG and GC samples excited by 980 nm LD (inset: enlarged fluorescence spectra at 400-416 nm)

Fig. 4. Fluorescence decay curves of PG and GC samples

Fig. 5. Fluorescence spectra of GC720 samples excited by 980 nm LD with different laser powers

Fig. 6. Double logarithmic variation of the integrated intensity at different peak positions of the GC720 sample with laser power

Fig. 7. Energy level diagrams of Er³⁺/Yb³⁺ system and its possible implementation of upconversion

Fig. 8. Fluorescence spectra of KLu₂F₇∶Er³⁺/Yb³⁺ nanocrystalline glass ceramics at different temperatures. (a) Unnormalized fluorescence spectra; (b) normalized fluorescence spectra

Fig. 9. Photosensitive properties of KLu₂F₇∶Er³⁺/Yb³⁺ nanocrystalline glass ceramics. (a) Linear Fitting of fluorescence intensity ratio to temperature; (b) temperature measurement sensitivity curve based on FIR