Network structure of multi-component sodium borosilicate glasses by neutron diffraction

Neutron diffraction structure study has been performed on multi-component sodium borosilicate based waste glasses with the composition of (65 − x)SiO _2. · xB ₂O ₃ · 25Na ₂O · 5BaO · 5ZrO ₂, x = 5–15 mol%. The maximum momentum transfer of the experimental structure factor was 30 Å ⁻¹, which made available to determine the distribution function with high r -space resolution. Reverse Monte Carlo modelling was applied to calculate several partial atomic pair correlation functions, nearest neighbor distances and coordination numbers have been revealed. The characteristic features of Si–O and Si–Si distributions are similar for all glassy samples, suggesting that the Si–O network consisting of tetrahedral SiO ₄ units is highly stable even in the multi-component glasses. The B–O correlations proved to be fairly complex, two distinct first neighbor distances are present at 1.40 Å and 1.60 Å, the latter equals the Si–O distance. Coordination number distribution analyzes has revealed 3 and four-coordinated boron atoms. The O–O distribution suggests a network configuration consisting of boron rich and silicon rich regions. Our findings are consistent with a structure model where the boron rich network contains mostly trigonal BO ₃ units, and the silicon rich network is formed by a mixed continuous network of ^[4]Si–O–Si ^[4] with several different ^[4]B–O–Si ^[4] and ^[3]B–O–Si ^[4] linkages.