Transport mechanisms in alkali silicate glasses

Abstract

From noble gas diffusion, conclusions on glass structure can be drawn. Some basic facts on the diffusion of ionic species in glasses are then presented, especially on the self diffusion of Na, K, Rb, and Cs in alkali silicate glasses. Self diffusion coefficients of Li in different lithium silicate glasses obtained recently are also reported. Different possibilities of the interdiffusion behavior are also presented. In the field of ionic diffusion in oxide glasses isotope effect determinations are of special interest. The well known results for Na ion migration are extended by data which were derived from the above mentioned Li diffusion experiments. For Li-containing glasses the isotope effect of the electrical conductivity is also considered. Combining the results on ionic self diffusion and on electrical conductivities by means of the extended Nernst-Einstein relation, and taking the results of isotope effect studies into consideration, conclusions about possible transport mechanisms can be drawn. New theoretical considerations on correlation effects in glasses are also presented.