Upconversion luminescence in transparent oxyfluoride glass ceramics containing hexagonal NaErF4

Abstract Transparent oxyfluoride glass ceramics containing hexagonal NaErF 4 nanocrystals were synthesized by a heat treatment of a precursor glass obtained by the melt quenching technique. Combined X-ray diffraction (XRD) and transmission electron microscopy (TEM) analysis revealed the formation of single phase nanocrystals in the glass ceramics. The enhancement of intensity and spectral change of upconversion luminescence (UCL) confirmed the presence of Er 3+ ions in the crystalline phase of the glass ceramics. Dominant energy transfer processes were identified using the rate equation formalism. Time-resolved site-selective spectroscopy studies at low temperatures were employed to elucidate the local structure of Er 3+ ions in the glass ceramics and microcrystalline NaErF 4 . The origin of multi-site formation in hexagonal NaErF 4 lattice is discussed.