Glass forming region, structure and properties of zinc iron phosphate glasses

Approximate glass forming region in the ZnO-Fe2O3-P2O5 ternary system was determined. Structure and properties of two compositional series of xZnO-20Fe2O3-(80 − x)P2O5 (A series, x = 20-40 mol.%) and xZnO-10Fe2O3-(90 − x)P2O5 (B series, x = 20-55 mol.%) were investigated. Phase identification was conducted by X-ray diffraction. Structural studies were carried out by Raman spectroscopy. Aqueous durability was measured by the glass dissolution rate in deionized water at 90 °C. Thermal properties were measured by differential scanning calorimetry and thermal dilatometry. Samples with ≥ 60 mol.% P2O5 can form glasses, whereas samples with ≤ 30 mol.% P2O5 cannot form glasses. Glass forming ability increases with increasing ZnO/Fe2O3 ratio for samples with fixed P2O5 content which locates in the range of 35-60 mol.% P2O5. Glass structure varies from metaphosphate to pyrophosphate with increasing ZnO content in each series. The structure variation leads to increase in density, aqueous durability and glass transition temperature and decrease in thermal expansion coefficient and thermal stability. Further improvement in thermal stability of these glasses with excellent aqueous durability in A and B series may improve their suitability for low-to-mid temperature sealing applications.