Effect of alkali and alkaline-earth metal oxides on the chemical strengthening properties of sodium alumino-silicate glasses

Silicate based alumino-sodium (SAS) glasses were fabricated with various alkali (Li2O and K2O) and alkaline-earth metal (MgO and CaO) oxides to study their influence on chemical strengthening characteristics such as surface compression stress (CS) and depth of layer (DOL) after ion exchange of Na+ with K+. Introducing Li2O instead of Na2O decreased DOL while increasing CS up to 5.0 mol. % of Li2O. In contrast, replacing Na2O content with K2O increased DOL while decreasing CS. When alkaline-earth oxides such as MgO and CaO were substituted for Na2O, both CS and DOL decreased. Micro-Raman spectroscopy was used to study structural changes induced by alkali and alkaline-earth oxides and their impact on ion exchange properties. The inter-diffusion coefficients of K+ ions were predicted by employing the Boltzmann-Matano equation to support the chemical strengthening effect of various alkali and alkaline-earth elements in SAS glasses.