Sodium and Potassium Mixed Effects on the Viscoelastic Behavior of Silicate Glasses

This study investigated the viscoelastic behavior and structural evolution of silicate glasses with the molar composition 70SiO2·(30 − x) Na2O·xK2O, where the molar ratio r = x/30 varied between 0, 0.25, 0.5, and 0.75. A notable “V”-shaped trend in relaxation activation energy (ΔHGt) was observed, with the energy reaching a minimum of 163.14 kJ/mol at r = 0.5. This trend exhibited a synergistic mixed alkali effect that significantly affected the viscoelastic properties of the glass. Raman spectroscopy analysis revealed dynamic structural reorganization within the [SiO4] network, transitioning from Q4 to Q3 for r < 0.5 and reverting to Q4 for r > 0.5 as the K2O content increased. These structural transformations provide atomic-scale evidence for the observed viscoelastic behavior. The findings offer critical insights into the mixed alkali effect on viscoelasticity, establishing a theoretical foundation for optimizing clad materials in optical fiber imaging arrays.