Effect of alkaline earth oxides on ceramization of LaF3 in aluminosilicate glass: 19F MAS-NMR study

Abstract 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 0.3 La 0.7 O 0.7 F 1.3 , instead of pure LaF 3 only.