'Universal' curve of ionic conductivities in binary alkali silicate glasses

The 'universal' curve of ionic conductivities in binary alkali silicate glasses is discussed. The σ-values for binary alkali-silicate glasses lie along a single 'universal' curve. The glass network expansion is the main parameter in determining the increase of the ionic conductivity in ionic conducting glasses. The expansion of the glass framework and the introduction of the alkali ions voids in the structure forming narrow pathways leads to two effects that lower the activation energy and promote the ionic conductivity.