Mixed electronic-ionic conductivity in transition metal oxide glasses containing alkaline ions

In alkali free transition metal oxide glasses conductivity is described by small polaron hopping. The carrier concentration is related to the concentration of transition metal ions in different valence states. Generally ionic conduction depends on the alkali concentration and ion mobility. Assuming that the motion of alkali ions and polarons is independent one may expect that the electrical conductivity increases with the increase in the alkali content. However, real transition metal oxide glasses containing alkali show various behaviors - from strong conductivity anomalies to conductivity weakly dependent on alkali content. A comparison of the electrical properties of iron phosphate glasses containing different amounts of sodium ions and copper oxide glasses to other TMO glass systems has been performed. The influence of the role of transition metal oxide in the glass forming network on the electrical properties of glass has been outlined (C) 2002 Elsevier Science B.V. All rights reserved.