Mechanical Relaxations in Mixed Alkali Silicate Glasses: II, Discussion*

Abstract

The internal friction of mixed Li‐Na, Li‐K, Li‐Rb, Li‐Cs, Na‐K, Na‐Rb, Na‐Cs, and K‐Rb silicate glasses is interpreted on the basis of the various explanations proposed for the mixed alkali effect. A direct correlation was found between the mechanical loss peak due to the stress‐induced movement of the alkali ions, i.e. the alkali peak, and the electrical loss properties. The large mechanical loss peak appearing when the alkalis are mixed was attributed to an interaction between dissimilar alkali ions such that an elastic dipole is formed. The absence of a comparable electrical loss peak was interpreted as indicating that the elastic dipole is electrically inactive. In glasses containing equimolar quantities of two alkalis, the activation energy and height of the new loss peak, i.e. the mixed peak, were more closely related to the size difference than to the mass difference of the alkali ions.