The structure of zinc polyphosphate glass studied by diffraction methods and 31P NMR

Zinc polyphosphate glasses with molar ratios, y=n(ZnO)/n(P2O5), ranging from 1.0 to 2.5 have been examined by using X-ray and neutron diffraction and 31P magic angle spinning nuclear magnetic resonance spectroscopy to extract information on their short-range, intermediate-range and submicroscopic structure. The depolymerization of the PO4 chains with decreasing P2O5 mol% content is quantitatively described by the Qn distributions determined by NMR. The shortening of the real-space distances, rm, extracted from the diffraction experiments, indicates a structural densification with progressive depolymerization. This effect correlates with the continuous increase in packing density of the ions, ρp. The Zn–O coordination number, NZnO, was found to be four across the entire polyphosphate concentration range. The presence of two differently-sized heterogeneity regions of electron density is indicated by the measured small angle X-ray scattering.