Influence of preparation conditions on diffusion in glasses

Abstract

It has been found that mass transport belongs to those properties which are clearly influenced by the mode of formation of a glass. Thermal history, microstructure and impurity states can be elucidated by performing suitable diffusion experiments. Referring to oxide glasses some of the relevant formation parameters and their influences on self diffusion and interdiffusion of ions and migration of gas atoms are compiled. The preparation method (especially for the case of vitreous silica), the atmosphere above the melt, and the particular thermal history of a specimen are important. Electrical conductivity is also influenced in a similar way. Moreover, the particular experimental conditions, i.e. how a diffusion experiment is conducted (both during the diffusion anneal and when the profile is determined), may also strongly influence the results. In order to be able to separate such effects from the real influence of the formation mode on diffusion, they have also to be discussed. In the melt state diffusion may be influenced by buoyancy convection. This can be overcome by performing the experiment under microgravity conditions in space.