Shear planes crystallographic

Crystallographic shear plane. Series of discrete shear phases are observed among the oxides of several transition metals. By progressive reduction, series of Ti 02 i, V 02 i phases are obtained from the dioxides, as Me 03 i phases may be related to trioxides such as M0O3 or WO3. An example of a crystallographic shear plane formation is schematically shown in Fig. 7.54. 

Role of Ciystallographic Shear Planes This area is tied to the subject of surface oxidation state. In redox kinetics it is believed that sites for hydrocarbon oxidation are different from that for reoxidation, and crystallographic shear planes (CSP) have been suggested to assist bulk oxygen movement between the sites 44,45,46,47), There have been a few studies of this phenomenon. In WO2.95 WO2.9 it has been shown CSPs are involved in oxygen transfer but... 

Non-stoichiometric oxides with high levels of disorder may adopt two modes of stabilization aggregation or elimination of point defects. Point defect aggregates forming clusters are examples of the former and extended defect structures like crystallographic shear-plane structures are examples of the latter. 

VOPO4 is reduced through the formation of crystallographic shear planes. 

In oxygen-deficient Nb205, and in mixed oxides of Nb and Ti, and Nb and W, the crystallographic shear planes occur in two sets at right angles to each other. The... 

Oxygen bacancies are commonly encountered in oxide perovskites. In AB03 unlike in W03, and Ti02 crystallographic shear planes are not found. Instead, a variety of superstructures are seen due to the ordering of vacancies. The brownmillerite phase of... 

Category (Hi) (layered structures with crystallographic shear planes)... 

The authors suggested that the M018O52 phase consists of crystallographic shear planes similar to crystalline M018O52, which would be similar in their XANES signature. The shear planes were also suggested by electron microscopy studies... 

Bennett RA, Poulston S, Stone P, Bowker M (1999) A LEED and STM study of crystallographic shear plane termination on a reduced TiOj(llO) surface. Phys Rev B 59 10341... 

Crystallographic shear planes (CS planes) are planar faults in a crystal that separate two parts of the crystal which are displaced with respect to each other. The vector describing the displacement is called the crystallographic shear vector (CS vector). Each CS plane causes the composition of the crystal to change by a small increment because the sequence of crystal planes that produces the crystal matrix is changed at the CS plane. (From this it follows that the CS vector must be at an angle to the CS plane. If it were parallel to the plane, the succession of crystal planes would not be altered and no composition change would result. A planar boundary where the displacement vector is parallel to the plane is more properly called an antiphase boundary.)... 

There is no need in these cases to relate the selectivity to the presence of C.S. planes, which are difficult to conceive in these kinds of ionocovalent structures. Recent HREM experiments made on (Te-Mo-0) system, catalyst for ammoxidation of propylene, have not revealed the presence of crystallographic shear planes (87). 

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