Rutile Superstructure of Sb0.9V1.1O4

1997 ◽  
Vol 53 (2) ◽  
pp. 221-230 ◽  
Author(s):  
A. R. Landa-Cánovas ◽  
S. Hansen ◽  
K. Ståhl
Keyword(s):  
Electron Diffraction ◽  
Structural Model ◽  
Rietveld Method ◽  
High Resolution Electron Microscopy ◽  
Rutile Structure ◽  
X Ray ◽  
Edge Sharing Octahedra ◽  
Resolution Electron ◽  
Diffraction Patterns ◽  
Convergent Beam

The structure of Sb0.9V1.1O4, antimony vanadium oxide, has been studied by powder X-ray diffraction, electron diffraction and high-resolution electron microscopy (HREM). The X-ray powder diffraction pattern showed only basic rutile reflections [a r = 4.6085 (1), c r = 3.0867 (1) Å] and the basic rutile structure was refined using the Rietveld method. A rutile superstructure was revealed when the sample was studied by electron diffraction. The electron diffraction patterns were indexed on the unit cell a = 21/2 a r , b = 21/2 b r , c = 2c r . Its space group, I41 md, was determined by means of convergent-beam electron diffraction (CBED). A structural model based on alternating cation ordering along c in the chains of edge-sharing octahedra is proposed and its electron diffraction patterns and HREM image are calculated and matched with the experimental ones.

Atomic structure of YB56 studied by digital high-resolution electron microscopy and electron diffraction

2001 ◽  
Vol 16 (1) ◽  
pp. 101-107 ◽  
Author(s):  
Takeo Oku ◽  
Jan-Olov Bovin ◽  
Iwami Higashi ◽  
Takaho Tanaka ◽  
Yoshio Ishizawa
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Electron Diffraction ◽  
High Resolution Electron Microscopy ◽  
Charge Coupled Device ◽  
X Ray ◽  
Resolution Electron ◽  
High Resolution Images ◽  
Diffraction Patterns ◽  
Simulated Images

Atomic positions for Y atoms were determined by using high-resolution electron microscopy and electron diffraction. A slow-scan charge-coupled device camera which had high linearity and electron sensitivity was used to record high-resolution images and electron diffraction patterns digitally. Crystallographic image processing was applied for image analysis, which provided more accurate, averaged Y atom positions. In addition, atomic disordering positions in YB56 were detected from the differential images between observed and simulated images based on x-ray data, which were B24 clusters around the Y-holes. The present work indicates that the structure analysis combined with digital high-resolution electron microscopy, electron diffraction, and differential images is useful for the evaluation of atomic positions and disordering in the boron-based crystals.

Structure determination of inorganic structures by HREM, Cip, and electron diffraction

1993 ◽  
Vol 51 ◽  
pp. 1204-1205
Author(s):  
Xiaodong Zou ◽  
V.G. Zubkov ◽  
Gunnar Svensson ◽  
Sven Hovmöller
Keyword(s):  
Image Processing ◽  
Electron Diffraction ◽  
Ccd Camera ◽  
High Resolution Electron Microscopy ◽  
X Ray Diffraction ◽  
X Ray ◽  
Resolution Electron ◽  
Diffraction Patterns ◽  
The Fourier Transform

High resolution electron microscopy (HREM) combined with crystallographic image processing (CIP) is becoming a powerful technique for solving inorganic structures. With the image processing systems CRISP and ELD, running on a personal computer, this technique can be easily established in other laboratories. HREM images and electron diffraction patterns are digitized by a CCD camera and transferred into a PC. Phases and amplitudes are extracted from the Fourier transform of the HREM images. For thin crystals of metal oxides, the phases obtained by HREM and CIP inside the Scherzer resolution of the microscope are identical to the x-ray structure factor phases.Electron diffraction extends to much higher resolution than EM images (beyond 1 Å). The quality of the amplitudes is also higher than that from images, since ED data is not affected by the contract transfer function (CTF). Amplitudes extracted by ELD are close to x-ray diffraction amplitudes (within 30%).

HREM Studies of Some Phases in the ZrO2-Nb2O5 System

1990 ◽  
Vol 48 (1) ◽  
pp. 40-41
Author(s):  
Margareta Sundberg ◽  
Bengt-Olov Marinder
Keyword(s):  
Electron Diffraction ◽  
High Resolution Electron Microscopy ◽  
Structure Type ◽  
X Ray ◽  
Resolution Electron ◽  
Commensurate Phase ◽  
Crystal Fragment ◽  
Diffraction Patterns ◽  
Unit Cell Dimensions ◽  
Block Structures

High resolution electron microscopy and x ray powder diffraction techniques were used to study samples of various compositions in the Nb2O5-rich part of the ZrO2-Nb2O5 system at 1500°C. A large number of fragments were also characterized by electron diffraction in combination with EDS analysis. Some HREM results concerning block structures formed in the above region have previously been reported.The x ray powder pattern of a ZrO2.9Nb2O5 sample indicated a phase isotypic with T-Nb2O5. The micrograph in Fig. 1, of a thin crystal fragment from that sample, illustrates a phase related to the UVO5 (m=2) structure type. The electron diffraction patterns showed an ordered commensurate phase (m=8) with unit cell dimensions similar to those reported for T-Nb2O5 and Ta30W2O81. The structure models of these two compounds are rather similar and differ mainly in the oxygen content.

Identification of a new trace 114R SiC by HREM

1999 ◽  
Vol 55 (2) ◽  
pp. 255-257 ◽  
Author(s):  
X. Y. Yang ◽  
G. Y. Shi ◽  
X. M. Meng ◽  
H. L. Huang ◽  
Y. K. Wu
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Electron Diffraction ◽  
Matrix Model ◽  
High Resolution Electron Microscopy ◽  
Stacking Sequence ◽  
X Ray Diffraction ◽  
X Ray ◽  
Resolution Electron ◽  
Diffraction Patterns

Using electron diffraction patterns and high-resolution electron microscopy (HREM), a trace 114R SiC in commercial α-SiC powder (mainly 6H SiC according to X-ray diffraction) has been discovered. In a hexagonal unit cell its stacking sequence is [(33)4(34)2]3, the periodicity along the c axis is 286.14 Å and a = b = 3.073 Å. 114R belongs to the structure series of (33) n34(33) m34 predicted theoretically by Pandey & Krishna [Mater. Sci. Eng. (1975), 20, 243–249] on the basis of the faulted matrix model.

Anisotropic radiation damage of potassium tetracyano platinate (KCP)

1978 ◽  
Vol 36 (1) ◽  
pp. 392-393
Author(s):  
N. Uyeda ◽  
E. J. Kirkland ◽  
B. M. Siegel
Keyword(s):  
Electron Diffraction ◽  
Radiation Damage ◽  
Structural Changes ◽  
High Resolution Electron Microscopy ◽  
Radiation Sensitivity ◽  
Resolution Electron ◽  
Damage Process ◽  
Diffraction Patterns ◽  
Fading Rate

The direct observation of structural change by high resolution electron microscopy will be essential for the better understanding of the damage process and its mechanism. However, this approach still involves some difficulty in quantitative interpretation mostly being due to the quality of obtained images. Electron diffraction, using crystalline specimens, has been the method most frequently applied to obtain a comparison of radiation sensitivity of various materials on the quantitative base. If a series of single crystal patterns are obtained the fading rate of reflections during the damage process give good comparative measures. The electron diffraction patterns also render useful information concerning the structural changes in the crystal. In the present work, the radiation damage of potassium tetracyano-platinate was dealt with on the basis two dimensional observation of fading rates of diffraction spots. KCP is known as an ionic crystal which possesses “one dimensional” electronic properties and it would be of great interest to know if radiation damage proceeds in a strongly asymmetric manner.

scholarly journals Structures of pseudo-decagonal approximants in Al−Co−Ni

2012 ◽  
Vol 370 (1969) ◽  
pp. 2949-2959 ◽  
Author(s):  
Sven Hovmöller ◽  
Linus Hovmöller Zou ◽  
Xiaodong Zou ◽  
Benjamin Grushko
Keyword(s):  
High Resolution Electron Microscopy ◽  
Limited Information ◽  
X Ray ◽  
X Ray Crystallography ◽  
Resolution Electron ◽  
Cell Dimensions ◽  
Diffraction Patterns ◽  
Quasi Crystals ◽  
Unit Cell Dimensions ◽  
Microscopy Images

Quasi-crystals shocked the crystallographic world when they were reported in 1984. We now know that they are not a rare exception, and can be found in many alloy systems. One of the richer systems for quasi-crystals and their approximants is Al−Co−Ni. A large series of pseudo-decagonal (PD) approximants have been found. Only two of them, PD4 and PD8, have been solved by X-ray crystallography. We report here the structures of PD1, PD2, PD3 and PD5, solved from the limited information that is provided by electron diffraction patterns, unit cell dimensions and high-resolution electron microscopy images.

Study of the Metamict Transformation in α-Quartz Using High-Resolution Electron Microscopy and Convergent Beam Electron Diffraction

1981 ◽  
Vol 6 ◽  
Author(s):  
M. R. Pascucci ◽  
J. L. Hutchison ◽  
L. W. Hobbs
Keyword(s):  
Electron Microscopy ◽  
Electron Diffraction ◽  
High Resolution Electron Microscopy ◽  
Convergent Beam Electron Diffraction ◽  
Transformation Model ◽  
Beam Electron ◽  
Surrounding Matrix ◽  
Resolution Electron ◽  
Two Stages ◽  
Convergent Beam

ABSTRACTThe metamict transformation under electron irradiation has been studied in α-quartz using transmission electron microscopy (TEM) and convergent-beam electron diffraction (CBD). The transformation occurs in two stages: heterogeneous nucleation of discrete disordered inclusions and a slower homogeneous loss of crystalline order in the surrounding matrix. Both features are attributable to solidstate radiolysis, a mechanism for which is proposed. Ultrahigh resolution TEM structure images and information from zeroth and high order Laue zones in CBD confirm that shortrange correlations are the first to be lost and that longerrange correlations persist well into the metamict transformation. A transformation model is advanced in which progressive disorder evolves from small displacements of individual [SiO4] coordination units, made possible by lowered connectivity, within a framework of long-range ordered material.

A structural model for charoite

2009 ◽  
Vol 73 (5) ◽  
pp. 883-890 ◽  
Author(s):  
I. V. Rozhdestvenskaya ◽  
T. Kogure ◽  
E. Abe ◽  
V. A. Drits
Keyword(s):  
Structural Model ◽  
High Resolution Electron Microscopy ◽  
Tubular Structures ◽  
X Ray Diffraction ◽  
X Ray ◽  
Selected Area Electron Diffraction ◽  
Resolution Electron ◽  
Xrd Patterns ◽  
Silicon Oxygen ◽  
Monoclinic Cell

AbstractThe crystal structure of charoite was investigated mainly by using selected-area electron diffraction (SAED), X-ray diffraction (XRD) and high-resolution electron microscopy (HREM). SAED and XRD patterns indicate that the structure has a monoclinic cell: a = 32.296, b = 19.651, c = 7.16 Å, β = 96.3° and V = 4517 Å3. The space group inferred from systematic absences and HREM images is P21/m. A model of the charoite structure is proposed that is based on the features of related Ca-alkaline silicate structures and HREM images. The structure of charoite consists of three different silicon-oxygen radicals (polymerized SiO4 tetrahedra) which are located between Ca polyhedra. Two of these radicals form continuous tubular structures comprising pectolite-like tetrahedral chains. Calcium polyhedra are joined to form blocks, each of which consists of four columns sharing edges and apices. Potassium and H2O molecules are probably located inside the tubular silicate radicals. From these results, a general formula is derived: K6-7(Ca,Na)18[(Si6O17)(Si12O30)(Si18O45)](OH,F)2.nH2O with two formula units in the unit cell (Z = 2).

Energy Filtered Imaging and Convergent Beam Electron Diffraction (CBED) in the Transmission Electron Microscope (TEM)

1997 ◽  
Vol 3 (S2) ◽  
pp. 973-974
Author(s):  
A.G. Fox ◽  
E.S.K. Menon ◽  
M. Saunders
Keyword(s):  
Electron Diffraction ◽  
Form Factors ◽  
Zone Axis ◽  
X Ray ◽  
Elemental Imaging ◽  
Energy Filtering ◽  
Transmission Electron ◽  
Diffraction Patterns ◽  
Convergent Beam ◽  
Single Objective

Over the last ten years TEMs have been developed that are capable of HREM, EDX, PEELS and diffraction using a single objective pole piece. More recently these TEMs have been equipped with the capability of energy filtering the electron beam after it has passed through the sample so that energy filtered images and electron diffraction patterns can be obtained. In this work the use of a Topcon 002B TEM equipped with a GATAN PEELS imaging filter (GIF) to generate zero-loss energy filtered zone axis CBED patterns and elemental images from inelastically scattered electrons will be described. An analysis of this energy filtered data indicates that elemental imaging using the GIF is an informative, but semiquantitative technique, whereas zero-loss energy filtered zone axis CBED patterns can be accurately quantified so that the two lowest-angle x-ray form factors of cubic elements can be measured with errors of the order of 0.1% or less.

Small-Spot Illumination For High-Resolution Electron Microscopy of Beam-Sensitive Specimens

1985 ◽  
Vol 43 ◽  
pp. 320-321
Author(s):  
Kenneth H. Downing ◽  
Robert M. Glaeser
Keyword(s):  
Electron Microscopy ◽  
Electron Beam ◽  
High Resolution ◽  
Electron Diffraction ◽  
High Resolution Electron Microscopy ◽  
Photographic Emulsion ◽  
Lateral Motion ◽  
Small Spot ◽  
Resolution Electron ◽  
Diffraction Patterns

The contrast observed in images of beam-sensitive, crystalline specimens is found to be significantly less than one would predict based on observations of electron diffraction patterns of the specimens. Factors such as finite coherence, inelastic scattering, and the limited MTF of the photographic emulsion account for some decrease in contrast. It appears, however, that most of the loss in signal is caused by motion of the specimen during exposure to the electron beam. The introduction of point and other defects in the crystal, resulting from radiation damage, causes bending and lateral motion, which degrade the contrast in the image. We have therefore sought to determine whether the beam-induced specimen motion can be reduced by reducing the area of the specimen which is illuminated at any one time.

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