A study of short and intermediate range order in zinc phosphate glasses

The short- and intermediate-range order of the polyphosphate glass network of the composition xZnO + (1 - x)P2O5 is invesligated, with 0.35 less than or equal to x less than or equal to 0.80. The short-range order is probed u sing P-31 solid-state magic angle spinning nuclear magnetic resonance (MAS NMR), liquid-state NMR and Raman spectroscopy. The results show an initial decrease in the amount of Q? sites, with an increasing number of Q(2) sites . The Q(2) sites reach a maximum concentration at the metaphosphate composi tion and then decrease as Q(1) and Q(0) sites become prevalent at the highe r modifier contents. The intermediate-range structure of xZnO + (1 - x)P2O5 glasses is studied using double quantum MAS NMR as well as high performanc e liquid chromatography measurements. These measurements show that the stru cture changes from cross-linked rings below the metaphosphate composition t o chains at and near the metaphosphate composition, and finally to dimers a nd isolated units at higher concentrations of the modifier. The dynamics of the intermediate-range structures are used to explain the effect of the co mposition on the T-g of the glass system. (C) 2001 Elsevier Science B.V. Al l rights reserved.