Hypersonic damping due to structural relaxation and fast-ion diffusion in (AgI${)}_{\mathrm{x}}$ (${\mathrm{AgPO}}_3$${)}_{1\mathrm{-}\mathrm{x}}$ melts

Brillouin scattering in melts of superionic (AgI${)}_{\mathrm{x}}$(${\mathrm{AgPO}}_3$ ${)}_{1\mathrm{-}\mathrm{x}}$ glasses demonstrates interactions between the diffusive motions of ${\mathrm{Ag}}^{+}$ and high-frequency phonons. Relaxation processes attributed to both structural relaxation and to ${\mathrm{Ag}}^{+}$ diffusion are revealed. For x≥0.4 the ${\mathrm{Ag}}^{+}$ diffusion becomes decoupled from the host matrix. The data are consistent with extrapolated dc-conductivity results.