Disorder–order phase transition in nanocrystalline titanium monoxide with two-sublattice ordering of structural vacancies

Atomic-vacancy ordering was achieved via prolonged annealing of nanocrystalline nonstoichiometric titanium monoxide TiO_y possessing the average crystal size of ∼30±10nm in vacuo in the temperature range of 300–1200K. The XRD and HRTEM data revealed the ordering based on the orthorhombic super-structures of M₂X₃ and M₃X₂ types (space group Immm), which are derived from the B1 structure of disordered cubic phase of γ-TiO.