Chemical diffusivity was measured in rutile single crystals at 1100C, perpendicular to the c-axis. Re-equilibration kinetics were considerably slowed down by a surface reaction in CO/CO2 mixtures while this effect vanished in pure oxygen atmospheres. The chemical diffusion coefficient D̃ was found to be nearly independent of x in TiO2−x.

A Reassessment of Chemical Diffusivity in TiO2−x. Morin, F.: Solid State Communications, 1986, 58[3], 161-4