Effect of composition changes on the structure and properties of phosphate glasses in the pyrophosphate region

The structures of phosphate glasses in the ultra- and polyphosphate region are well-investigated. Discontinuous changes of the properties in the composition range around 50 mol% P2O5 (transition from network to chain-like structures) are known. The present work is concerned with the structural transition of chain-like phosphate glasses to pyrophosphate glasses. P-31 MAS NMR investigations were used for the quantitative structural analyses of pyrophosphate and mixed pyrophosphate/orthophosphate glasses. Several chemical and physical properties of these glasses were determined in dependence on composition and structure. The investigated phosphate invert glasses are very sensitive to additives. Therefore, some important properties of phosphate invert glasses and glass-ceramics can be controlled by addition of relatively small and highly charged cations.