The effect of phase separation on short- and intermediate-range order in high-silica Li2O–SiO2 glasses

Wide-angle neutron diffraction measurements have been performed on single-phase and phase-separated high-silica glasses in the system Li2O–SiO2. The structure factors of the single-phase glasses vary modestly with increasing Li2O concentration compared to the changes observed when Na2O or K2O is added to SiO2, and vestiges of the intermediate-range order characteristic of v-SiO2 are retained to 33 mol % Li2O. The structure factors of single-phase and phase-separated glasses are identical to within 1%–2%, indicating that phase separation results in very minor disruptions to local atomic arrangements. When combined with evidence obtained from previous studies, these data indicate that single-phase high-silica glasses in this system contain compositional heterogeneities analogous to those produced by phase separation.