Influence of ion exchange on liquid–liquid phase separation in alkali borosilicate glasses: effect of ion-exchange-induced metastable glass homogenization

Experimental results of studying the metastable liquid–liquid phase separation and homogenization induced by ion exchange in (15-x)Li2O · xNa2O · 35B2O3 · 50SiO2 glass-forming system are presented. Both a homogeneous under-surface layer in a phase-separated glass and a phase-separated under-surface layer in a homogeneous glass have been formed by an ion exchange technique. The Li-for-Na ion exchange in the glass with x=15 led to phase-separated layers while the Na-for-Li ion exchange in the phase-separated glass with x=5 led to the homogeneous vitreous layers. These effects and the conditions that produce them are discussed from the viewpoint of phase equilibria in the system involved.