Acoustic properties and diffusion in superionic glasses

An ultrasonic study of the loss characteristics and sound velocity was carried out in AgI-Ag2O-B2O3 glasses as a function of temperature and silver-compound concentration. From the behavior of the sound velocity in (Ag2O)y(B2O3)1-y, the formation of fourfold-coordinated boron ions is suggested. This increases rapidly, as a function of y, until y≃0.25; for larger y, a strong production of singly bonded oxygen ions (nonbridging oxygen ions) prevails, which weakens the glassy network. From the analysis of the attenuation peaks in terms of a relaxation-time Gaussian-type distribution, arising from the thermally activated relaxation of mobile silver ions, it is argued that there exists a similarity between the ion motion in a stress field and in an electric one. By way of this analogy and by combining the ultrasonic results with the dc conductivity data in (AgI)x[(Ag2O)y(B2O3)1-y]1-x, the ion-jump distances are calculated. The behavior with AgI concentration is consistent with the structural hypothesis of the existence of silver ions differently bonded and mobile in the glassy matrix.