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 investigated, with 0.35⩽x⩽0.80. The short-range order is probed using 31P 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 Q3 sites, with an increasing number of Q2 sites. The Q2 sites reach a maximum concentration at the metaphosphate composition and then decrease as Q1 and Q0 sites become prevalent at the higher modifier contents. The intermediate-range structure of xZnO+(1−x)P2O5 glasses is studied using double quantum MAS NMR as well as high performance liquid chromatography measurements. These measurements show that the structure changes from cross-linked rings below the metaphosphate composition to chains at and near the metaphosphate composition, and finally to dimers and isolated units at higher concentrations of the modifier. The dynamics of the intermediate-range structures are used to explain the effect of the composition on the Tg of the glass system.