Local Atomic Structures for Tunable Ordered Arrangements of Crystallographic Shear Planes in Titanium-Chromium Oxide Natural Superlattices

2021 ◽  
Author(s):  
Shunta Harada ◽  
Shunya Sugimoto ◽  
Naoki Kosaka ◽  
Miho Tagawa ◽  
Toru Ujihara
Keyword(s):  
Chromium Oxide ◽  
Atomic Structures ◽  
Crystallographic Shear ◽  
Shear Planes

The thermodynamics of the titanium + oxygen system: an isothermal gravimetric study of the composition range Ti3O5 to TiO2 at 1304 K

1973 ◽  
Vol 274 (1245) ◽  
pp. 627-661 ◽  
Keyword(s):  
Composition Range ◽  
Hysteresis Loops ◽  
Reasonable Assumption ◽  
Titanium Oxides ◽  
Oxygen System ◽  
Crystallographic Shear ◽  
Data Points ◽  
Shear Structure ◽  
The Many ◽  
Shear Planes

The compositions of titanium oxide samples at 1304 K have been studied by, as far as possible, equilibrating them with (H2 + H aO) gas buffer mixtures of various compositions. The high precision with which the mass, and therefore the sample’s composition, was determined reveals that complete equilibrium is rarely attained, even after several days in a constant ambient: at most compositions there is gross hysteresis. Two composite hysteresis loops exist in the regions occupied by the (121) and (132) crystallographic shear structure families. Between these loops the oxidation and reduction paths are very nearly coincident: this is the region in which a change in composition can be accommodated by varying only the orientation and not the number of crystallographic shear planes. A third hysteresis loop is believed to exist between the (132) loop and the composition of slightly reduced rutile. A plausible explanation of the behaviour is developed. All the observations appear to be consistent with those from parallel electron microscope studies of reduced ‘rutile’. Nucleation of the product phase appears to be the most important factor affecting the behaviour in the region Ti30 5 to Ti40 7, as would be expected from a consideration of their structures. The differences between the behaviour observed by us and that reported by other workers is believed to be only apparent: it results from (a) the higher precision of our measurements, and (b) the much higher density and number of data points we have acquired. Various thermodynamic data are calculated for the many higher titanium oxides on the basis of a reasonable assumption for deducing approximate equilibrium oxygen potentials from the observed values. Most of these have not previously been available. By incorporating Zador’s (1967) data for T i0 199 to T i0 1999 we deduce for ^Ti30 5+ i 0 2 = TiOa (rutile), AG® (1304 K) = — 78.3 kj mol-1 compared with — 79.4 kj mol-1 in the JANAF tables. The stabilities of the Tiw0 2w_1 phases with respect to mixtures of the (n— 1) and (w+1) neighbours are seen to be extremely small ( —104 J/mol of Ti70 13, i.e. — 5.2 J/mol of atoms), and to decrease with increasing n. 1

scholarly journals Coupling of bias-induced crystallographic shear planes with charged domain walls in ferroelectric oxide thin films

2016 ◽  
Vol 94 (10) ◽  
Author(s):  
Myung-Geun Han ◽  
Joseph A. Garlow ◽  
Matthieu Bugnet ◽  
Simon Divilov ◽  
Matthew S. J. Marshall ◽  
...  
Keyword(s):  
Thin Films ◽  
Domain Walls ◽  
Oxide Thin Films ◽  
Crystallographic Shear ◽  
Shear Planes ◽  
Ferroelectric Oxide

Mechanism of the morphotropic transformation between the rutile and corundum structural types

2003 ◽  
Vol 59 (4) ◽  
pp. 456-462 ◽  
Author(s):  
H. Katzke ◽  
R. Schlögl
Keyword(s):  
Simple Model ◽  
Phase Segregation ◽  
Transformation Process ◽  
Transformation Mechanism ◽  
One Dimensional ◽  
X Ray ◽  
Structural Types ◽  
Crystallographic Shear ◽  
Diffraction Patterns ◽  
Shear Planes

The rutile/corundum structural transformation which is based on crystallographic shear is discussed in terms of a one-dimensional disorder model. The transformation process is described by a simple model based on the structural relationship between the rutile-type and corundum-type phases. The model is able to handle randomly spaced crystallographic shear planes, the so-called Wadsley defects, as well as clustered CS planes. Calculations hsow that simply modifying the probability parameters of the model can lead to phase segregation. X-ray powder diffraction patterns are calculated for the proposed transformation mechanism as a function of the stoichiometry x in MO2−x in order to show the influence of such defects on the intensities and linewidths of the Bragg reflections.

Equilibrium between point defects and crystallographic shear planes

1983 ◽  
Vol 74 (1-4) ◽  
pp. 247-252 ◽  
Author(s):  
G. Boureau ◽  
J. F. Marucco
Keyword(s):  
Point Defects ◽  
Crystallographic Shear ◽  
Shear Planes

scholarly journals New modular oxide structures using lone pair cations as "chemical scissors"

2014 ◽  
Vol 70 (a1) ◽  
pp. C227-C227
Author(s):  
Maria Batuk ◽  
Dmitry Batuk ◽  
Artem Abakumov ◽  
Joke Hadermann
Keyword(s):  
Oxygen Deficiency ◽  
Lone Pair ◽  
Complex Oxides ◽  
Shear Plane ◽  
Structure Type ◽  
Twin Plane ◽  
Coordination Environment ◽  
Crystallographic Shear ◽  
New Compounds ◽  
Shear Planes

"It is known that lone pair cations, such as Bi3+ or Pb2+ have a flexible coordination environment that enables them to operate as ""chemical scissors"". Their flexibility reduces the strain that would otherwise be present at the interfaces separating structure modules. We have found that in complex oxides it allows many variants of interfaces, for example crystallographic shear planes or (non)conservative twin planes in structures, enabling the synthesis of new structural families. A common characteristic for all these new compounds is the presence of magnetical frustration. As a first example, this concept allowed to introduce crystallographic shear planes into the perovskite structure, a feat that was considered highly unlikely before. This allowed to generate a new anion deficient perovskite based homologous series AnBnO3n-2 (n = 4 - 6). There is magnetic frustration at the crystallographic shear plane separating the perovskite blocks, due to competing FM and AFM interactions. Also incommensurately modulated perovskites can be obtained, for example (Pb,Bi)1-xFe1+xO3-y. These arise by replacing Bi3+ with Pb2+, which introduces an oxygen deficiency, which is then accommodated by periodically spaced CS planes to reduce the coordination of the A-cations at the interface. The flexible coordination environment of Bi3+ and Pb2+ makes them ideally suited for these A cation positions. Other possibilities were encountered in BiMnFe2O6 and Bi4Fe5O13F. In BiMnFe2O6 the Bi3+ induces the existence of a non-conservative twin plane. The result is a new structure type with hcp structured modules. In Bi4Fe5O13F, the Bi3+-cations separate layers with magnetically frustrated Cairo lattices."

Precipitation phenomena in non-stoichiometric oxides I. Pairs of crystallographic shear planes in reduced rutiles

1984 ◽  
Vol 391 (1801) ◽  
pp. 351-372 ◽  
Keyword(s):  
High Resolution Electron Microscopy ◽  
Specimen Preparation ◽  
Cooling History ◽  
Chemical Systems ◽  
Interstitial Defect ◽  
Resolution Electron ◽  
Crystallographic Shear ◽  
Precipitation Phenomena ◽  
New Phenomena ◽  
Shear Planes

High-resolution electron microscopy, in conjunction with controlled specimen preparation procedures, has enabled the nature and structure of the small defects existing within the nonstoichiometric phase TiO 2-x (0 ≤ x ≤ 0.01) to be investigated. In particular, the precipitation of pairs of crystallographic shear planes (c. s. p.) and their subsequent separation has been observed. The atomic mechanisms involved in c. s. p. nucleation and growth and the eventual evolution to an ordered c. s. structure have been elucidated by using new linear cationic interstitial defect structural models. The results emphasize the decisive influence that cooling history has on the microstructures observed at room temperature and suggest that similar new phenomena will be discovered in observations of other non-stoichiometric chemical systems.

On Diffraction Patterns of Structures Containing Regular Crystallographic Shear Planes

1992 ◽  
Vol 45 (9) ◽  
pp. 1397 ◽  
Author(s):  
G Harburn ◽  
BH Parry ◽  
RJD Tilley ◽  
RP Williams
Keyword(s):  
Electron Diffraction ◽  
Fourier Analysis ◽  
Tungsten Trioxide ◽  
Two Dimensional ◽  
Analysis Study ◽  
Shear Structures ◽  
Crystallographic Shear ◽  
Diffraction Patterns ◽  
Special Case ◽  
Shear Planes

The appearances of the diffraction patterns expected for the phases derived from tungsten trioxide by crystallographic shear have been deduced by Fourier analysis. Study of electron- diffraction patterns and optical analogues confirms the predictions of the theory. The results have been generalized to a two-dimensional continuum of 'infinitely adaptive structures' by use of the shift lattice, of which the crystallographic shear structures are a special case.

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