Effect of alkaline earth oxides on ceramization of LaF_3 in aluminosilicate glass: ~(19)F MAS-NMR study

摘要

Local environment of fluorine atoms in the lanthanum oxyfluoride aluminosilicate glasses and glass-ceramics modified by alkaline earth oxides, i.e. MgO, CaO and BaO, was studied by solid state ~(19)F MAS-NMR spectroscopy. The effect of the type and concentration of the modifier on the formation of crystalline LaF_3 phase was determined, as a function of heat treatment conditions. In all series of glasses studied, the F-Me(n), but no Na-F species were observed. The presence of F-La,Ba(n) units, in which fluorine is coordinated both by lanthanum and barium, was detected in the Ba-glass. Supplementary XRD analysis of this series confirmed that an increase of barium contents leads to the formation of Ba_(0.)3La_(0.7)O _(0.7)F_(1.3), instead of pure LaF_3 only.