Internal Friction of Aluminoborosilicate Glasses with Small Amounts of Alkalis

Abstract

The internal friction of K₂O-Na₂O-B₂O₃-Al₂O₃-SiO₂ and Na₂O-SrO-B₂O₃-Al₂O₃-SiO₂ glasses was measured by a free damping method, and the minimum alkali content for exhibiting the mixed alkali or mixed cation effect was determined. In the former glasses, two independent peaks at lower temperatures caused by the movement of K and Na ions were observed for glasses containing less than 4mol% alkali content. In the latter system, similar peaks were recognized for glasses containing less than 7mol% total cation contents. These results confirmed that no mixed alkali effect appears for glasses containing a small content of alkalis and that the effect of mixed cation effect is less pronounced than the mixed alkali effect.