Mechanical Relaxations in Mixed‐Alkali Silicate Glasses: I, Results

Abstract

The internal friction of silicate glasses containing mixtures of Li‐Na, Li‐K, Li‐Rb, Li‐Cs, Na‐K, Na‐Rb, Na‐Cs, and K‐Rb was measured from ‐180° to 500°C at a frequency of 0.4 Hz. Values for the density, index of refraction, and dynamic shear modulus are also reported. With small additions of a second alkali, a new internal friction peak was observed in addition to the two peaks originally present in the glasses containing only one alkali. The magnitude of this new peak was especially sensitive to small amounts (less than 1 mol%) of a second alkali. Activation energies are given for the alkali peak in Li‐Cs glasses and for the new internal friction peak in Li‐Na glasses.