Orientation domains in vacancy-ordered titanium monoxide

Abstract

This paper presents a study on orientation domains in the vacancy-ordered titanium monoxide TiO(x). Transmission electron microscopy analysis revealed the co-existence of 12 possible TiO(x) monoclinic domain variants, which are induced by the cubic-to-monoclinic phase transition attributed to the Ti and O vacancy ordering. These 12 monoclinic domain variants which are predicted by group theory might be randomly arranged. Furthermore, several hours of electron beam irradiation can lead to the vacancy ordering-disordering transition (i.e. monoclinic-to-cubic phase transformation) in TiO(x). Our results shed light on the structural characteristics in TiO(x) nanostructures and thus contribute to the fabrication and design of the related nanostructures.

Switchable Intrinsic Defect Chemistry of Titania for Catalytic Applications

“…∆ TiO has two polymorphs based on the vacancy distribution. If the vacancies are randomly distributed it leads to disordered cubic phase, and the other polymorph has ordered vacancies with monoclinic symmetry [83,[102][103][104][105][106]. ∆ It is metallic in nature due to the high content of vacancy channels [107].…”

Orientation domains in a monoclinic Mg–Al–O phase

“…The nucleation of the monoclinic MgAl x O y under high temperature (above 1173 K) indicates that this might be a potentially important mineral component of the Earth's lower mantle under conditions of high temperature and pressure. Theoretically, the occurrence of the domain variants can be interpreted on the basis of group theory, which predicts that decreasing the symmetry of the space group during the phase transition should result in the formation of domain structures (Wondratschek & Jeitschko, 1976;Guo et al, 2013;Xiong et al, 2013;Jia et al, 2013;Xu et al, 2014). In the current case, the monoclinic MgAl x O y phase may nucleate as a result of symmetry reduction compared with the cubic MgAl 2 O 4 (space group Fd 3 3m).…”

Growth mechanism of titanium monoxide TiOxon a reduced calcium titanate CaTi2O4surface

“…2( f )] can be indexed as the [010] axis based on the disordered TiO x cubic phase (space group Fm 3 3m, lattice parameter a = 0.4185 nm). Further analysis of the literature indicates that the superstructural reflections can be associated with the presence of ordered monoclinic domain variants (space group A2/m, lattice parameters a = 0.5855, b = 0.9340, c = 0.4142 nm and = 107.53 ), the occurrence of which can be attributed to the lower symmetry resulting from the structural phase transition (Guo et al, 2013). The fact that we could confirm only two phases (CaTi 2 O 4 and TiO x ) in our sample helps to identify the phases in the HRTEM images presented below.…”