A new model was proposed to describe the non-Arrhenius conductivity observed in a series of optimized fast ion-conducting silver thioborosilicate glasses. Its essential feature was that the mobile cations were thought to conduct from one open site to the next open available site and, in this process, naturally by-pass filled or unavailable sites. The thermal excitation of cations out of their equilibrium sites was taken to be the mechanism for generating the open and available anion sites. Hence, the mean free path for a drifting cation between open available sites was directly proportional to the activated carrier concentration and was therefore a strong function of temperature. There was also a weak temperature dependence for the mean free path that arose because the capture cross-section for a drifting cation by a stationary anion trap varies with drift velocity, e.g. the momentum of a fast cation allows it to closely approach an anion trap while avoiding capture or back scattering. The capture cross section of a cation by an anion trap was large because the interaction was electrostatic rather than geometric in origin. The model was shown to be in good agreement with all of the experimental data for silver thioborosilicate glasses and all model parameters were physically defined and reasonable in value. The model predicted a simple high-temperature conductivity dependence that was not exponential in nature. The model was also suggested to be valid for other materials such as crystalline conductors.

Trapping Model for the Non-Arrhenius Ionic Conductivity in Fast Ion-Conducting Glasses. S.W.Martin, D.M.Martin, J.Schrooten, B.M.Meyer: Journal of Physics - Condensed Matter, 2003, 15[16], S1643-58