Mixed Transition Ion Effect in Certain Polaronic Semiconductors

Abstract

The presence of vanadium and iron in phosphate glasses has been found to exhibit properties similar to the mixed alkali effect observed in oxide glasses. While conduction in the latter is caused by a classical barrier crossing mechanism of alkali ions, a quantum-mechanical process, comprising hopping of small polarons, is generally accepted to be the mechanism of charge transport in phosphate glasses containing transition metals. The substitution of one transition ion by another significantly increases dc resistivity activation energy for dc conduction and glass transition temperature, reaching maxima at an intermediate transition ion ratio.