Sol-gel glass-ceramic materials containing CaF2: Eu3+ fluoride nanocrystals for reddish-orange photoluminescence applications

Abstract

CaF2:Eu3+ glass-ceramic sol-gel materials have been examined for reddish-orange photoluminescence applications. The transformation from precursor xerogels to glass-ceramic materials with dispersed fluoride nanocrystals was verified using several experimental methods: differential scanning calorimetry (DSC), thermogravimetric analysis (TG), X-ray diffraction (XRD), transmission electron microscopy (TEM), infrared spectroscopy (IR-ATR), energy dispersive X-ray spectroscopy (EDS) and photoluminescence measurements. Based on luminescence spectra and their decays, the optical behavior of Eu3+ ions in fabricated glass-ceramics were characterized and compared to those of precursor xerogels. In particular, the determined luminescence lifetime of the 5D0 excited state of Eu3+ ions in nanocrystalline CaF2:Eu3+ glass-ceramic materials is significantly prolonged in comparison with prepared xerogels. The integrated intensities of emission bands associated to the 5D0 → 7F2 electric-dipole transition (ED) and the 5D0 → 7F1 magnetic-dipole transition (MD) are changed drastically during controlled ceramization process of xerogels. This implies the efficient migration of EuEu3+ ions from amorphous silicate sol-gel network into low-phonon energy CaF2 nanocrystals.