Upconversion luminescence in erbium doped transparent oxyfluoride glass ceramics containing hexagonal NaYF₄ nanocrystals

In this work transparent erbium doped oxyfluoride glass ceramics containing hexagonal NaYF₄ nanocrystals has been prepared by melt-quenching and subsequent heat treatment of the precursor glass. The formation of β-NaYF₄ was confirmed by X-ray diffraction measurements. The overall intensity of the upconversion luminescence of the glass ceramics sample is 2 orders of magnitude higher than that of the precursor glass. The observed enhancement of the efficiency is explained by the incorporation of Er³⁺ into low-phonon β-NaYF₄ crystalline phase.