Optical and upconversion properties of Er3+-doped oxyfluoride transparent glass-ceramics containing SrF2 nanocrystals

Er3+-doped oxyfluoride transparent glass and glass-ceramics (GCs) containing SrF2 nanocrystals were prepared and their spectroscopic properties were investigated. The formation of SrF2 nanocrystals in GCs has been confirmed by x-ray diffraction (XRD) and transmission electron microscopy. The Judd-Ofelt (JO) parameters have been evaluated from absorption spectra of the Er3+-doped glass and GCs, which are used to predict radiative properties for some important luminescence levels of Er3+ ions in glass and GCs. The XRD and JO parameters suggest that the Er3+ ions are progressively incorporated into the SrF2 nanocrystals in the GCs compared with glass. The up-conversion luminescence intensity increases significantly in GCs with increase in time of thermal treatment. The lifetime of the S-4(3/2) level of the Er3+ ions in GCs is found to be slightly higher than that in the glass due to the incorporation of Er3+ ions into the lower phonon energy of SrF2 nanocrystals in the GCs.