VISCOUS-FLOW MECHANISM OF OXYFLUORIDE GLASSES RELATED TO GLASS STRUCTURE

The viscosities of 30PO.(70-x)SnF2.xSnO glasses were measured over a w ide temperature range, and the viscous now mechanism is compared with those of silicate and fluoride glasses. It was found that the viscosit y and activation energy decrease as the concentration of fluoride ions increases. The viscosity can be expressed by the Fulcher equation ove r a wide temperature range except for the glass of the low fluorine co ntent. Sn2+ ions are thought to play the role of network modifiers and the viscous now behavior is determined by weak Sn-F and P-F bonds.