Sodium diffusion in glasses during electron irradiation

Abstract

Sodium migration in glasses during electron probe microanalysis is investigated. We observe the change in x-ray emission as a function of time and for various incident electron doses. A specific protocol is used in this study: independently drawn from a multivariate statistical analysis of the data and from an a priori simple model, an exponential decay of the Na signal is clearly established. This model for Na+ migration is only based on an electric field with a linear decrease behavior as a function of depth and it accounts for the main experimental results with no evidence of an incubation time prior to ion migration. The electron densities and the fraction of incident electrons remaining trapped into the glass are deduced from an estimate of ion mobility. The maximum electric field values at the coating/glass interface are also given.