It was noted that, under ambient conditions, this oxide (with a wide range of homogeneity of the B1 lattice structure) was stable only with vacancies on both the Ti and the O sub-lattices. Even at the stoichiometric composition, the vacancy content was large and equal to about 15 to 16at% on the 2 sub-lattices. The vacancies could be eliminated only at high pressures (8GPa) and high temperatures (1920K). Elimination of the vacancies was accompanied by an increase in the lattice constant from 0.41796 to 0.42062nm. At low temperatures, the Ti and O atoms and the vacancies were ordered and formed a superstructure (space group: C2/m). In order to explain the stability of a structure with vacancies on both sub-lattices, the electron structure and the charge state of the vacancies were studied. Electron micro-diffraction here yielded information concerning the distribution of lattice vacancies. Positron annihilation techniques which were sensitive to the charge state of lattice vacancies were used.

Identification of Atomic Vacancies in Titanium Monoxide by Electron Micro-Diffraction and Positron Annihilation. Valeeva, A.A., Rempel, A.A., Muller, M.A., Reichle, K.J., Tang, G., Sprengel, W., Schaefer, H.E.: Physica Status Solidi B, 2001, 224[2], R1, 3