Electron microscope study of non-stoichiometric titania

Abstract

The distribution and coexistence of Magn61i phases (TinO2n_ 1 ) with n = 4, 5 and 6 in hydrogen-reduced Ti02 has been investigated using transmission electron microscopy. The major phase was Ti~O 9. Ti6011 was found in TisO 9 grains in the form of narrow lamellae ( < 10 nm wide) epitaxially intergrown on (001 ) planes. The Ti407 phase, however, was never observed as a second phase in TisO 9 grains but formed single-phase grains. The TisO 9 phase was twinned on the (01 1 )r planes of the rutile subcell structure and the Ti6011 lamellae were pinned to these twins. This pinning may be responsible for the hysteresis that occurs during the oxidation-reduction of non-stoichiometric Ti02. We also report observations on in situ oxidation of the line phases.

Defect‐Mediated Anisotropic Lattice Expansion in Ceramics as Evidence for Nonthermal Coupling between Electromagnetic Fields and Matter

“…The simulation thus suggests that if an externally applied field (MWR in our case) can indeed nucleate vacancies, then the nearby oxygen atom will form an addition interstitial–vacancy pair to minimize the potential energy. This understanding is aligned with the idea of oxygen vacancies found in nonstoichiometric TiO 2 and at the same time agrees with the peaks corresponding to oxygen interstitials seen under XPS, in Figure . Because the volume was kept constant during the simulation, there is no change in the lattice parameters.…”

Titanium Dioxide Engineered for Near-dispersionless High Terahertz Permittivity and Ultra-low-loss

“…Crystal structure then changes from corner-shared octahedrals to edge-shared octahedrals or edge-shared octahedrals to plane-shared octahedrals 26 . It is reported that, in extremely reduced TiO 2 , crystallographic shear planes would exist as an ordering structure with a regular spacing, resulting in a homologous series of stoicheimetrically-defined intermediates with general formula Ti n O 2n−1 , also known as Magnéli phase 27 . However, crystallographic shear planes were also observed in pure TiO 2 ceramics, conventionally sintered in air 28 .…”

Sintered alumina with low dielectric loss

“…Pure stoichiometric TiO 2 is white in color, the ceramics sintered in air show a darkening to a brown-tan color, this being due to the fact that TiO 2 is easily reduced. [12][13][14] The samples of alumina doped with titania display a bluish tinge and a slight darkening from their usual white color and this may be due to a stoichiometric deficiency of oxygen. 14 It might be expected that doping with TiO 2 would reduce the Q due to the inclusion of a high-loss component and possible reduction of the oxide.…”