Electrical properties of polycrystalline TiO₂ at elevated temperatures. Electrical conductivity

IN MEMORIAM. This paper is dedicated to the memory of Dr. J. Bruce Wagner, Jr. (1926-2006), long time Professor of Materials Science and Engineering at the Northwestern University, Evanston, IL and Regents Professor of the Arizona State University, Tempe, AZ. Professor Wagner was prominent scientist in the area of solid-state science, electrochemistry and high temperature chemistry. He served as Director of the Material Research Centre at the Technological Institute of Northwestern University, Director of the Centre for Solid State Science at the Arizona State University. He was also the President of the Electro-chemical Society. The present work reports the electrical properties for high purity polycrystalline TiO₂ using the measurements of electrical conductivity in the temperature range 1123-1323 K and in the gas phase of controlled oxygen activity (10^-13 Pa < p(O₂) < 10⁵ Pa). The slope of the log σ vs. log p(O₂) dependence is -1/5.4, which is considered in terms of mixed electronic and ionic compensation. The electrical conductivity data within the n - p transition were used for the determination of the conductivity components related to electrons, electron holes and ions. These data were used for the determination of the n-p transition point. The band gap determined from the conductivity components related to electronic charge carriers is equal to 2.8 eV.