Effect of B₂O₃ substitution for SiO₂ in alkali aluminoborosilicate glasses on chemical strengthening

Abstract

This study reports the strengthening effect of partially substituting SiO₂ with B₂O₃ in aluminoborosilicate (ALBS) glasses. Specifically, it investigates how the B₂O₃ addition affects the ion-exchange behavior of the glass. The base composition of ALBS glass is 13Na₂O–5K₂O–7MgO–15Al₂O₃–12B₂O₃–48SiO₂ (mol %). In the prepared samples, the proportion of B₂O₃ was varied from 0 to 16 mol %. The Na⁺/K⁺ inter-diffusion coefficient of each sample was estimated from the K⁺ ion concentration profile collected along the cross-section of each sample after immersion in molten KNO₃ at (Tg × 0.83) K (where Tg is the glass transition temperature) for 8 h. Adding only a small amount of B₂O₃ drastically changed the K⁺ ion concentration profile. In contrast, the activation energy of the Na⁺/K⁺ inter-diffusion was almost independent of B₂O₃ content. These results suggest that the B₂O₃ incorporated in the glasses simply acts as a flux component. These findings are useful for designing compositions that strengthen ion-exchanged glasses.