Ionic Conductivity and Disorder Modes in Borate Glass Systems

It is shown that ionic conductivity in ${\left(\mathrm{AgI}\right)}_x{\left({\mathrm{Ag}}_2\mathrm{O}·{\mathrm{B}}_2{\mathrm{O}}_3\right)}_{1-x}$ amorphous compounds is describable as a coupling between disorder modes of glass-forming borate units and ${\mathrm{Ag}}^{+}$ translational degrees of freedom. A model is presented for the ionic conductivity where ions and disorder modes are represented by two pseudospin variables which interact through an exchange term. This model, as applied to the interpretation of conductivity activation energies and prefactors in borate glass systems, is discussed.