Zinc borate glasses: properties, structure and modelling of the composition-dependence of borate speciation

Abstract

The short-range order of binary zinc borate glasses, xZnO-(1−x)B2O3, has been quantitatively described as a function of ZnO content over the entire glass forming range for the first time, to the best of our knowledge. Multiple spectroscopic techniques (11B NMR, Raman, infrared) reveal detailed structural information regarding borate speciation and network connectivity, and a new model for quantifying the molar fractions of short-range order units is proposed. A consistent thermal history dependence for the fraction of tetrahedral boron (N4) is well accounted for by the proposed model. The model predicts density within 0.1% of experimental values and N4 to within 1% of NMR values. The intermediate character of four-coordinated zinc in borate glasses of this series is evident by the far infrared profiles and the glass transition temperature behavior, which decreases non-monotonically with increasing ZnO content.