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

Abstract

Zinc polyphosphate glasses with molar ratios, y= n(ZnO)/ n(P 2O 5), 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 PO 4 chains with decreasing P 2O 5 mol% content is quantitatively described by the Q n distributions determined by NMR. The shortening of the real-space distances, r m, 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, ρ p. The Zn–O coordination number, N ZnO, 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.