Defect Disorder of TiO_2. Equilibrium Constant for the Formation of Oxygen Vacancies

摘要

The present work reports the electrical conductivity for Nb-doped TiO_2 single crystal at elevated temperatures (1223 K-1298 k) in the gas phase of controlled oxygen activity [10~(-10) Pa < p(O_2) < 10 Pa]. The effect of oxygen activity on the electrical conductivity is considered in terms of defect disorder of TiO_2 and the related semiconducting properties. Application of the mass action law and the related charge neutrality conditions results in equilibrium constant for the formation of oxygen vacancies in TiO_2 (rutile): K_1 ={(72.2[J/mol])/R}-{(438[KJ/molK])/(RT)} It is shown that the ionization degree of niobium in Nb-doped TiO_2 is 70%.