The mechanism of alkali-ion diffusion in Na, Li and K di-silicate melts was studied by means of quasi-elastic neutron scattering. Although scattering on alkali atoms involved coherent and incoherent contributions, only incoherent scattering contributed to the quasi-elastic signal of the diffusing alkali atoms at timescales of up to about 60ps. Such de-coupling of incoherent and coherent correlations was a signature of alkali-ion diffusion along channels that were embedded within the relatively immobile Si-O network.

Formation of Channels for Fast-Ion Diffusion in Alkali Silicate Melts - a Quasielastic Neutron Scattering Study. F.Kargl, A.Meyer, M.M.Koza, H.Schober: Physical Review B, 2006, 74[1], 014304 (5pp)