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

## TL;DR

This study explores how mixing sodium and potassium affects the viscoelastic properties of silicate glasses, revealing a 'V'-shaped trend and structural changes.

## Contribution

The paper provides atomic-scale evidence for the mixed alkali effect on viscoelasticity in silicate glasses.

## Key findings

- A 'V'-shaped trend in relaxation activation energy was observed, with a minimum at a 50% K2O molar ratio.
- Raman spectroscopy showed structural reorganization in the [SiO4] network with changes in Q4 to Q3 configurations.
- The findings establish a theoretical foundation for optimizing materials in optical fiber imaging arrays.

## Abstract

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.