The self-diffusion of 44Ti in slightly reduced rutile. TiO2-δ, was measured along the c-axis at 1000 to 1100C under oxygen pressures of between 0.2 and 10-18atm (table 14). This permitted the determination of the defect structure of TiO2-δ. For oxygen pressures of between 10-13 and 10-16atm at 1058.4C, random tetravalent titanium atoms were the predominant defects. The enthalpy of motion was determined to be 57.03kcal/mol. From the activation energy at 1.69 x 10-16atm, the enthalpy of formation of tetravalent titanium interstitials was deduced to be 276kcal/mol. For oxygen pressures of less than 10-16atm at 1058.4C, the tracer diffusion coefficient exhibited a continual decline as the oxygen pressure was lowered. Comparisons with thermogravimetric studies, and consideration of the similarity in structure of non-stoichiometric point defect phases and the first homologous series phase, indicated that the order-disorder transition retained a considerable degree of short-range order, below the critical concentration, in the form of Wadsley defects.

Diffusion of Titanium in Slightly Reduced Rutile. Akse, J.R., Whitehurst, H.B.: Journal of Physics and Chemistry of Solids, 1978, 39[5], 457-65