VISCOSITY AND DENSITY OF MOLTEN BARIUM ZIRCONATE AND RELATED MELTS

Viscosity and density of molten ZrF4-BaF2 mixtures have been measured using the oscillating cup method and the Archimedean method respective ly. The viscosity had a marginal minimum around the composition BaF2.2 ZrF4, and increased significantly towards the composition BaF2.ZrF4. T he density of molten ZrF4-BaF2 increased with the BaF2 content, while the volume thermal expansion decreased. The effect of the valence of t he counter cation on the viscosity was studied by substitution of the glass modifier BaF2 with NaF or LaF3. The viscosity increased with the valence of the counter cation. These fragile glass-forming systems ar e more comparable to ionic glasses than typical network glasses. The p hysical properties of the molten fluorides are discussed in relation t o complex formation and the ionic character of the melts.