Properties and Structures of Tin Borophosphate Glasses

The effects of B2O3-additions on the properties and structures of two series of Sn(II)-borophosphate glasses were determined. The addition of up to 28 mol% B2O3 to a 66.7SnO-33.3P 2O5 base glass (series I), and the substitution of up to 13 mol% B2O3 for P2O5 in the same base glass (series II) increase Tg from 265 °C to 357 °C and 306 °C, respectively, while reducing the aqueous corrosion rates (at 40 °C) by an order of magnitude. The refractive index of the series I glasses decreases slightly, from 1.784 to 1.725, and increases for series II, to 1.834, at 632.8 nm. Raman spectroscopy reveals that borate additions to both series reduce the number of P-O-P linkages by converting pyrophosphate anions to orthophosphate anions. 11B NMR spectra indicate that tetrahedral borophosphate units, B(OP)4, are initially formed when B2O3 is added to the Sn-pyrophosphate base glass. More complex tetrahedral and trigonal borate sites form when B2O3 contents exceed about 10 mol%