Electrical Properties and Defect Chemistry of TiO₂Single Crystal. I. Electrical Conductivity

TLDR

The study measures electrical conductivity of high‑purity TiO₂ single crystals from 1073–1323 K under controlled oxygen activities (10⁻¹³–10⁵ Pa) and analyzes the data in terms of electron, hole, and ion conduction components. The measurements show that oxygen vacancies dominate defect chemistry across the studied temperature and oxygen activity ranges, revealing electronic and ionic lattice charge compensations at low and high activities, respectively, and yielding activation energies of 125–205 kJ mol⁻¹ for conductivity, 218 kJ mol⁻¹ for electrons, 34 kJ mol⁻¹ for holes, 227 kJ mol⁻¹ for ions, a defect motion enthalpy of 4 kJ mol⁻¹, a band gap of 3.1 eV, and enable determination of the n‑p demarcation line.

Abstract

The present work reports the electrical properties of high-purity single-crystal TiO(2) 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 10(5) 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(sigma) = 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) = 227 kJ.mol(-1)), and the enthalpy of motion for electronic defects (DeltaH(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.