ALKALI DIFFUSION AND ELECTRICAL-CONDUCTIVITY IN SODIUM-BORATE GLASSES

The diffusion coefficient of sodium, 22Na, and silver, 110Ag, and electrical conductivity for sodium borate glasses (4-24 mol% Na2O) has been measured from 100°C to slightly below the glass transition temperature, Tg. Unlike silicate glasses where the self-diffusion coefficient is much larger than the impurity diffusion coefficient, DNa and DAg had close to the same magnitude in the sodium borate glasses. In some glasses, DAg was slightly larger than DNa. Na2O-Ag2O-B2O3 glasses show a relatively small mixed alkali effect, despite the significant mass difference between Ag(≈108) and Na(≈23). It is concluded that the mixed alkali effect is more dependent upon the difference in ionic radii rather than differences in mass. © 1979.