CONDUCTIVITY BEHAVIOR OF HIGH-SILICA GLASSES WITH VARIED CONCENTRATIONS OF SODIUM-IONS

The low‐frequency conductivity of silica glasses containing 5% B2O3 and from 0.02 to 6.7% Na2O is extrapolated to dc values and analyzed in terms of temperature and concentration dependence. The concentration dependence of the conductivity occurs exclusively in the activation enthalpy. This prevents an analysis of the number of ions participating in the conduction in all but one sample for which tracer diffusion data gave a correlation factor of unity in the Nernst‐Einstein equation. The concentration dependence of the activation enthalpy was analyzed empirically. The activation enthalpy varies linearly with sodium‐sodium separation or jump distance. This result suggests that, at low Na concentrations, the conducting ions execute several separate motions between nonequilibrium sites before reaching the nearest equivalent site. The empirical equation is shown to fit activation energy data for silica glasses containing from 0.06 to 40% Na2O. Copyright © 1979, Wiley Blackwell. All rights reserved