In alkali-free transition metal oxide glasses conductivity was described by small polaron hopping. The carrier concentration was related to the concentration of transition metal ions in different valence states. Generally ionic conduction depended upon the alkali concentration and ion mobility. Assuming that the motion of alkali ions and polarons was independent one may expect that the electrical conductivity increased with the increase in the alkali content. However, real transition metal oxide glasses containing alkali showed various behaviors – from strong conductivity anomalies to conductivity weakly dependent upon alkali content. A comparison of the electrical properties of iron phosphate glasses containing different amounts of Na ions and copper oxide glasses to other TMO glass systems was performed. The influence of the role of transition metal oxide in the glass forming network on the electrical properties of glass was outlined.

Mixed Electronic–Ionic Conductivity in Transition Metal Oxide Glasses Containing Alkaline Ions. R.J.Barczynski, L.Murawski: Journal of Non-Crystalline Solids, 2002, 307-310, 1055-9