Electrical conductivity of TiO₂ within n-p transition Part I - Verification of defect disorder model

The present paper reports semiconducting properties and the related defect disorder for undoped TiO₂ single crystal using measurements of the electrical conductivity. Isothermal changes of the electrical conductivity as a function of oxygen activity were determined within oxygen activities ranging between 10 Pa and 75 kPa and temperatures between 1073 and 1323 K. The electrical conductivity data, involving both n and p type regimes, are considered in terms of defect disorder assuming that the predominant mobile defects are oxygen vacancies, which are compensated by immobile titanium vacancies. Application of this model led to the determination of the electrical conductivity components related to electrons, electron holes and ions. The determined empirical relationships between electrical conductivity and oxygen activity may be used for predicting the effect of experimental conditions on semiconducting properties of TiO₂. The activation energy for the standard conductivity component of electrons and holes is 226 and 102 kJ mol^-1 respectively.