Acoustic properties and diffusion in superionic glasses

An ultrasonic study of the loss characteristics and sound velocity was carried out in AgI-${\mathrm{Ag}}_2$O-${\mathrm{B}}_2$ ${\mathrm{O}}_3$ glasses as a function of temperature and silver-compound concentration. From the behavior of the sound velocity in ${\left({\mathrm{Ag}}_2\mathrm{O}\right)}_y{\left({\mathrm{B}}_2{\mathrm{O}}_3\right)}_{1-y}$, the formation of fourfold-coordinated boron ions is suggested. This increases rapidly, as a function of $y$, until $y\simeq 0.25$; 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 ${\left(\mathrm{AgI}\right)}_x{\left[{\left({\mathrm{Ag}}_2\mathrm{O}\right)}_y{\left({\mathrm{B}}_2{\mathrm{O}}_3\right)}_{1-y}\right]}_{1-x}$, 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.