Properties and structure of binary tin phosphate glasses

The properties and structures of binary xSnO*(100 − x)P2O5 (50 ≤ x ≤ 70 mol%) glasses were evaluated. The glass transition temperatures (Tg), determined by differential thermal analysis (DTA), range from 246 to 264 °C, for glasses prepared under identical conditions. The refractive index (nD) increases from 1.701 to 1.833 as x increases from 50 to 70, and the Abbe number (νD) decreases from 29.1 to 20.4 over the same range. Infrared spectroscopy was used to estimate water contents in the glasses, which decreased with an increase in SnO content, from about 1570 ppm OH for x = 50 to about 50 ppm OH for x = 70, for glasses quenched from melts held at 1000 °C for 15 min. Residual water affects thermal properties, like Tg, and variations in water contents due to differences in melt processing explain the wide variety of glass properties reported in the literature. Raman spectroscopy indicates that progressively shorter phosphate chains are present in the structures of the binary Sn-phosphate glasses with increasing SnO contents.