Investigation of the crystallization process in oxyfluoride glass ceramics codoped with Er/Yb

The oxyfluoride glass ceramics are important up-conversion luminescent materials. Er³⁺/Yb³⁺-codoped transparent oxyfluoride glasses were prepared by melt-quenching and subsequently heat-treated at different times and temperatures, and the crystallization process of fluoride nanocrystals from the glass was investigated. X-ray diffraction (XRD) and fluorescence spectra investigations reveal that fluoride nanocrystals are distributed homogeneously among the glassy matrix for the sample doped with Er³⁺/Yb³⁺. The crystallization process indicates that heat-treatment temperature influences the size of fluoride nanocrystals, while heat-treatment time influences their concentration. Moreover, the red emission intensities increase due to the incorporation of Er³⁺/Yb³⁺ into the fluoride nanocrystals under different heat-treatment methods, which are studied by fluorescence spectra.