Assuming that the glass network structure containing channels for ionic migration is established at the glass transition temperature during cooling and is perfectly rigid below this temperature, the properties of non-exchanged and as-melted mixed alkali glasses are compared. Alkali ions introduced by ion exchange below the glass transition temperature bring the glass matrix into a state of internal strain by elastic expansion or contraction of ionic sites. In an as-melted mixture alkali glass, an ion-channel mismatch produces a similar strained state, resulting in large internal friction and the so-called thermometer effect. The change in molar volumes due to ion exchange is calculated on the basis of Eshelby's misfitting sphere theory. The molar volumes of ion-exchanged glasses calculated are close to those observed for as-melted mixed alkali glasses.
