Concentration dependence of Raman scattering in superionic glasses (AgI)x(Ag2OH2O3)1−x

We have studied low-frequency Raman scattering in (AgI${)}_{\mathit{x}}$(${\mathrm{Ag}}_2$O⋅${\mathrm{B}}_2$ ${\mathrm{O}}_{31\mathrm{-}\mathrm{x}}$ superionic glasses as a function of AgI content. In particular, we found evidence for a quasielastic contribution. Such scattering has been interpreted as being due to relaxation modes originating from the jumping of silver ions in the available sites of the local network of AgI units. The intensity $I_L$ of the quasielastic scattering (of Lorentzian shape, centered at zero frequency) has been correlated with the number of silver ions participating in the conduction. The variation of $I_L$ as a function of silver iodide concentration is exponential, implying cooperative effects. This is shown also by conductivity measurements.