Electron Transport in Single Crystals of Niobium Dioxide

Abstract

We have made measurements of the Hall effect and resistivity as well as of thermoelectric power in the temperature range 300–450 K. The results of these measurements are interpreted in terms of a small polaron model of conduction. Additionally, our resistivity and thermoelectric power measurements were extended to 1200 K in an attempt to elucidate the nature of the transition in conductivity occurring in the range 1071–1103 K. For the c direction, this transition appears to be from a semiconducting to a metallic state and a possible explanation for this is given in terms of a lattice distortion model.