Crystallization and luminescence properties of Eu3Â +-doped ZrF4-BaF2-NaPO3 glass and glass ceramics

Fluorozirconate-phosphate glasses of the composition ZrF4-BaF2-NaPO3 doped with EuF3 have been investigated by the methods of differential thermal (DTA) and X-ray diffraction (XRD) analysis, nuclear magnetic resonance (19F NMR, 19F and 31P MAS NMR), luminescence spectroscopy, and scanning electron microscopy (SEM). The thermal behavior of the fabricated glasses is similar to that of fluorozirconate glasses - NaPO3 dopants decrease the glass transition temperature (Tg) from 300 down to 250 °C and increase the glass stability to crystallization (ΔТ). Resonance lines in 19F NMR spectra correspond to the glass fluorozirconate network, whereas the 19F and 31P MAS NMR data indicate to the presence of bridge and end fluorine atoms in the structure and to low degree of depolymerization of phosphate chains. Thermal treatment in the temperature range Tg-Тх1 induces crystallization of nanosized particles, whose composition corresponds to β-BaZrF6. The SEM data indicate to the globular structure of glasses and synthesized glass ceramics, while the particle sizes are within the range 20-160 nm. The intensity of luminescence of glasses doped with europium(III) increases upon doping with 2.5-10 mol% of NaPO3 and decreases in glass ceramics. In glass and glass ceramics, europium ions are predominantly present in the fluorozirconate matrix.