Electrical properties and defect chemistry of TiO₂ single crystal. I. Electrical conductivity

The present work reports the electrical properties of high-purity single-crystal TiO₂ from measurements of the electrical conductivity in the temperature range 1073-1323 K and in gas phases of controlled oxygen activities in the range 10^-13 to 10⁵ Pa. The effect of the oxygen activity on the electrical conductivity indicates that oxygen vacancies are the predominant defects in the studied ranges of temperature and oxygen activities. The electronic and ionic lattice charge compensations were revealed at low and high oxygen activities, respectively. The determined semiconducting quantities include: the activation energy of the electrical conductivity (E_σ = 125-205 kJ·mol^-1). the activation energies of the electrical conductivity components associated with electrons (E_n=218 kJ·mol^-1), electron holes (E _p = 34 kJ·mol^-1), and ions (E_i = 221 KJ·mol^-1) and the enthalpy of motion for electronic defects (ΔH_m = 4 kJ/mol). The electrical conductivity data are considered in terms of the components related to electrons, holes, and ions. The obtained data allow the determination of the n-p demarcation line in terms of temperature and oxygen activities. The band gap determined from the electronic component of the electrical conductivity is 3.1 eV.