LiYF4-nanocrystal-embedded glass ceramics for upconversion: glass crystallization, optical thermometry and spectral conversion

Abstract

Glass ceramics (GCs) can perfectly integrate nanocrystals (NCs) into bulk materials. Herein, GCs containing LiYF₄ NCs were fabricated via a traditional melt-quenching method and subsequent glass crystallization. Structural characterization was carried out via X-ray diffraction (XRD), transmission electron microscopy (TEM), selected area electron diffraction (SAED), and scanning transmission electron microscopy high-angle annular dark-field (STEM-HAADF) analysis, suggesting the precipitation of LiYF₄ NCs from a glass matrix. Taking Eu³⁺ as a structural probe, the spectrographic features provide compelling evidence for the partition of dopants. In particular, intense upconversion (UC) emission was achieved when co-doped with Yb³⁺ and Er³⁺. Temperature-dependent UC emission behaviour was also established based on the fluorescence intensity ratio (FIR) of Er³⁺, to study its properties for optical thermometry. Furthermore, spectral conversion was attained through cross relaxation (CR) between Ce³⁺ and Ho³⁺, tuning from green to red with various Ce³⁺ doping concentrations. There is evidence that LiYF₄ NC-embedded GCs were favorable for UC, which may be extremely promising for optical thermometry and spectral conversion applications. This work may open up new avenues for the exploration of GC materials for expansive applications.