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%).

Structure determination of a new polymorph of TiO2 by high-resolution electron microscopy and computer simulations

1989 ◽  
Vol 47 ◽  
pp. 416-417
Author(s):  
Jillian F. Banfield ◽  
David R. Veblen ◽  
David J. Smith
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Electron Diffraction ◽  
Computer Simulations ◽  
High Resolution Electron Microscopy ◽  
X Ray Diffraction ◽  
X Ray ◽  
Naturally Occurring ◽  
Resolution Electron

A new, naturally occurring polymorph of TiO2 has been identified. This mineral forms lamellae generally only a few nanometers wide in anatase from two localities near Bintal Valais, Switzerland. The abundance of this mineral in anatase is too low to allow investigation by X-ray diffraction. The unit cell determined by electron diffraction is triclinic, with a = 0.754 nm, b = 0.448 nm, c = 0.616 nm, α = 78.90°, β = 124.55°, γ = 96.54°. The coherently intergrown lamellae are oriented with b parallel to a of anatase; the interface is parallel to (103) anatase.

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.

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.

Interfacial reaction products and film orientation in YBa2Cu3O7−x on zirconia substrates with and without CeO2 buffer layers

1993 ◽  
Vol 8 (11) ◽  
pp. 2785-2798 ◽  
Author(s):  
G.L. Skofronick ◽  
A.H. Carim ◽  
S.R. Foltyn ◽  
R.E. Muenchausen
Keyword(s):  
Interfacial Reaction ◽  
High Resolution Electron Microscopy ◽  
Buffer Layers ◽  
Reaction Products ◽  
X Ray Diffraction ◽  
Orientation Relationships ◽  
X Ray ◽  
Resolution Electron ◽  
Ybco Superconductors ◽  
Diffraction Patterns

Thick film (1.2 μm) YBCO superconductors grown by pulsed laser deposition on unbuffered and CeO2-buffered single crystal (001)-oriented yttria-stabilized zirconia (YSZ) substrates have been investigated. YBCO and YSZ react to form BaZrO3 (BZO), whereas YBCO and CeO2 react to form BaCeO3. Reaction phases were examined by θ-2θ and four-circle x-ray diffraction and high resolution electron microscopy. Three orientation relationships identified for the unbuffered films were (i) (001)YBCO ‖ (011)BZO ‖ (001)YSZ with [110]YBCO ‖ [100]BZO ‖ [100]YSZ, (ii) (001)YBCO ‖ (001)BZO ‖ (001)YSZ with [110]YBCO ‖ [100]BZO ‖ [100]YSZ, and (iii) (001)YBCO ‖ (001)BZO ‖ (001)YSZ with [100]YBCO ‖ [100]BZO ‖ [100]YSZ. The results suggest that for films grown at typical deposition temperatures, YBCO epitaxy is established before the interfacial reaction occurs. The presence of BaCeO3 in buffered films grown at high temperatures (790 °C) was confirmed by θ-2θ scans and selected area diffraction patterns.

Incommensurate modulated disorder in Ba0.85Ca2.15In6O12

1996 ◽  
Vol 52 (5) ◽  
pp. 780-789 ◽  
Author(s):  
G. Baldinozzi ◽  
F. Goutenoire ◽  
M. Hervieu ◽  
E. Suard ◽  
D. Grebille
Keyword(s):  
High Resolution Electron Microscopy ◽  
Microscopy Study ◽  
Electron Microscopy Study ◽  
X Ray ◽  
Incommensurate Structure ◽  
Resolution Electron ◽  
Complete Determination ◽  
Incommensurate Modulation ◽  
Diffraction Patterns

The tunnel structure of the oxide Ba0.85Ca2.15In6O12 has been revisited. A mono-incommensurate modulation has been evidenced by electron diffraction. The simultaneous refinement of X-ray and neutron powder diffraction patterns has allowed a complete determination of the incommensurate structure [P3({{1}\over{3}} {{1}\over{3}}γ)]. The existence of a modulated disorder, affecting Ba and Ca atoms, has been pointed out. The occupancy modulation concerning Ba and Ca atoms located on the hexagonal tunnel axis induces a modulation of the Ba—O bond lengths. The high-resolution electron microscopy study has shown the existence of twinning domains and of crystal regions possessing a defective arrangement of the modulation.

Ordered structure formation in the flux-grown Ba(Mg1/3Ta2/3)O3 single crystals

2001 ◽  
Vol 16 (6) ◽  
pp. 1593-1599 ◽  
Author(s):  
Yu-Chang Lee ◽  
Chen-Chia Chou ◽  
Dah-Shyang Tsai
Keyword(s):  
Electron Diffraction ◽  
Single Crystals ◽  
Annealing Time ◽  
High Resolution Electron Microscopy ◽  
Maximum Intensity ◽  
Ordered Structure ◽  
X Ray Diffraction ◽  
Resolution Electron ◽  
Higher Temperature ◽  
Diffraction Patterns

Formation of ordered structure in flux-grown Ba(Mg1/3Ta2/3)O3(BMT) single crystals was studied using x-ray diffraction, electron diffraction, and high-resolution electron microscopy. The low-temperature-grown crystals exhibited no sign of B-site ordering. Annealing at 1500 °C induced the 1:2 ordered phase, and its content increased with the annealing time. The superlattice diffraction peaks were broad initially; they sharpened rapidly with the annealing time. Diffuse superlattice reflections were found in electron diffraction patterns of 1500 °C annealed BMT; they turned into sharp reflections under long annealing time or higher temperature, 1600 °C. The intensity of diffuse reflections was sparsely distributed, but the maximum intensity location was determined in the digitized recording of image plate. The maximum intensity sites of two diffuse reflections in the 〈111〉 direction deviated from the presumed 1/3 and 2/3 positions and shifted towards the center. The diffuse reflection and the deviation from regular positions were interpreted as the composition modulation during B-site cation diffusion.

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.

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.

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.

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