Mechanical relaxations in single and mixed alkali silicate glasses

Damping measurements carried out in the mixed alkali silicate glasses evidence the classical mixed alkali peak and point out new experimental features. Firstly, two satellite relaxation peaks are superimposed to the mixed alkali peak and correspond to the ionic and NBO peaks, respectively. Moreover, Arrhenius plot of the mixed alkali peak shows that the apparent activation energy is different below and above 340 K. These experimental results are discussed using the recent models for the alkali effect and the Meyer-Bunde model for mechanical relaxation in ionic glasses below the glass transition temperature Tg.