Formation of channels for fast-ion diffusion in alkali silicate melts: A quasielastic neutron scattering study

Abstract

The mechanism of alkali ion diffusion in sodium, lithium, and potassium disilicate melts is studied by means of quasielastic neutron scattering. Although scattering on alkali atoms comprises coherent and incoherent contributions, only incoherent scattering contributes to the quasielastic signal of the diffusing alkali atoms on time scales up to about 60 ps. Such a decoupling of incoherent from coherent correlations is a signature of an alkali ion diffusion along channels that are embedded in the relatively immobile Si-O network.