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

The short-range order of binary zinc borate glasses, x ZnO-(1- x )B 2 O 3 , 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 ( 11 B 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 ( N 4 ) is well accounted for by the proposed model. The model predicts density within 0.1% of experimental values and N 4 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.