To investigate the defect structures of slightly reduced rutile, channelling experiments were performed on a slightly reduced specimen, and on a stoichiometric one, using 6MeV protons accelerated by a cyclotron. In an angular scan of the back-scattering yield of protons from Ti ions with respect to the [001] axial channel, a peak was observed along the [001] direction only in the reduced specimen. By analysis of the angular scan it was confirmed that the main defects in slightly reduced rutile were Ti interstitial ions. These were located within about 0.4Å of the [001] mid-channel axis. This result supported interpretations of electron paramagnetic resonance experiments to the effect that a so-called C-center was a Ti interstitial ion.

Investigation of Ti Interstitials in Slightly Reduced Rutile (TiO2) by Means of Channeling Method. Yagi, E., Koyama, A., Sakairi, H., Hasiguti, R.R.: Journal of the Physical Society of Japan, 1977, 42[3], 939-46