Anelastic relaxations in AgI-doped borophosphate glasses

An ultrasonic study ( 5 – 30 MHz ) of the loss characteristics in glasses of the “quaternary” systems AgI:Ag2O:P2O5:B2O3 was carried out in the 100 – 400 K temperature range. The loss behavior is characterized by a broad peak that shifts to higher temperatures with the frequency: The height and the temperature location of the peak are respectively increasing and decreasing functions of the AgI content. Thermally activated relaxation of Ag+ ions, weakly bonded and mobile in the glassy network, are assumed as origin of the observed dissipative processes. The experimental data was fitted by a Gaussian-like distribution of relaxation times and such an analysis permits us to obtain some parameters, connected with the microscopic arrangement of the mobile ions: The most probable activation energy Em, the width of the distribution Eo and the deformation potential B, expressing the coupling between the ultrasonic stress and the system. The behavior of these parameters with the AgI content suggests interesting conclusions about the possible influence of the glass structure on the ionic dynamics.