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Title: Electron diffraction study of lizardite 1T with stacking faults

Abstract

The stacking faults observed in the structure of the mineral lizardite 1T belonging to the polytype group A are investigated using the digital oblique-texture electron diffraction patterns, difference Fourier-potential maps, and model diffraction patterns obtained for this compound. Numerical simulation of the diffraction profiles along the first (the 02l and 11l reflections) and second (the 20l and 13l reflections) ellipses in the oblique-texture electron diffraction patterns is performed for finite sequences of ten layers with the use of the Markovian statistical model in the quasi-homogeneous approximation. The specific features of the intensity distributions along the first and second ellipses are associated with the manifestation of translational (displacements of the layers by {+-}b/3) and orientational (rotations of the layers through an angle of 180{sup o}) defects of the layer stacking, respectively. For both ellipses, the experimentally observed intensity distributions are in the best agreement with the diffraction profiles calculated for stacking faults at a content of approximately 25%, the short-range order parameter S = 1, and the maximum degree of ordering in the layer alternation. It is demonstrated that the irregularities revealed in the layer alternation in the structure of lizardite 1T (which is characterized by an identical orientation of themore » adjacent layers) arise from layer displacements by {+-}b/3 and, to a considerable extent, from the formation of sequences with opposite orientations of the adjacent layers. As a result, the structure of lizardite 1T nanocrystals involves a combination of layer sequences that are typical of structures belonging to the polytype groups A and D.« less

Authors:
 [1]
  1. Russian Academy of Sciences, Institute of Geology of Ore Deposits, Petrography, Mineralogy, and Geochemistry (Russian Federation), E-mail: anzhu@igem.ru
Publication Date:
OSTI Identifier:
21090954
Resource Type:
Journal Article
Resource Relation:
Journal Name: Crystallography Reports; Journal Volume: 52; Journal Issue: 2; Other Information: DOI: 10.1134/S1063774507020071; Copyright (c) 2007 Nauka/Interperiodica; Article Copyright (c) 2007 Pleiades Publishing, Inc; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; APPROXIMATIONS; ELECTRON DIFFRACTION; LAYERS; MARKOV PROCESS; MINERALS; NANOSTRUCTURES; SIMULATION; STACKING FAULTS; STATISTICAL MODELS

Citation Formats

Zhukhlistov, A. P. Electron diffraction study of lizardite 1T with stacking faults. United States: N. p., 2007. Web. doi:10.1134/S1063774507020071.
Zhukhlistov, A. P. Electron diffraction study of lizardite 1T with stacking faults. United States. doi:10.1134/S1063774507020071.
Zhukhlistov, A. P. Thu . "Electron diffraction study of lizardite 1T with stacking faults". United States. doi:10.1134/S1063774507020071.
@article{osti_21090954,
title = {Electron diffraction study of lizardite 1T with stacking faults},
author = {Zhukhlistov, A. P.},
abstractNote = {The stacking faults observed in the structure of the mineral lizardite 1T belonging to the polytype group A are investigated using the digital oblique-texture electron diffraction patterns, difference Fourier-potential maps, and model diffraction patterns obtained for this compound. Numerical simulation of the diffraction profiles along the first (the 02l and 11l reflections) and second (the 20l and 13l reflections) ellipses in the oblique-texture electron diffraction patterns is performed for finite sequences of ten layers with the use of the Markovian statistical model in the quasi-homogeneous approximation. The specific features of the intensity distributions along the first and second ellipses are associated with the manifestation of translational (displacements of the layers by {+-}b/3) and orientational (rotations of the layers through an angle of 180{sup o}) defects of the layer stacking, respectively. For both ellipses, the experimentally observed intensity distributions are in the best agreement with the diffraction profiles calculated for stacking faults at a content of approximately 25%, the short-range order parameter S = 1, and the maximum degree of ordering in the layer alternation. It is demonstrated that the irregularities revealed in the layer alternation in the structure of lizardite 1T (which is characterized by an identical orientation of the adjacent layers) arise from layer displacements by {+-}b/3 and, to a considerable extent, from the formation of sequences with opposite orientations of the adjacent layers. As a result, the structure of lizardite 1T nanocrystals involves a combination of layer sequences that are typical of structures belonging to the polytype groups A and D.},
doi = {10.1134/S1063774507020071},
journal = {Crystallography Reports},
number = 2,
volume = 52,
place = {United States},
year = {Thu Mar 15 00:00:00 EDT 2007},
month = {Thu Mar 15 00:00:00 EDT 2007}
}
  • Stacking faults in lizardites 1T (polytype group A) have been studied by analyzing the oblique-texture electron diffraction patterns in combination with a numerical simulation of diffraction patterns. The simulation of diffraction profiles was performed for finite (10-layer) sequences using the statistical Markov model in the quasi-homogeneous approximation. Diffraction criteria are revealed, which indicate the presence of defects in lizardite 1T; these defects are related to the change in the layer orientation by 180 Degree-Sign and displacements of adjacent layers by a/3. It is shown that in the case of the statistical distribution of defects, along with pairs of adjacent layersmore » with layer packing features typical of polytype groups D and B, there are also sequences of layers 1T(A), correspondingly rotated by 180 Degree-Sign or displaced by a/3 and 2a/3 with respect to the layers in the 1T matrix. The data obtained give deeper insight into the variations in layer packing in lizardites 1T.« less
  • The temperature dependence of the structure of the high-T{sub c} superconductor Y{sub 2}Ba{sub 4}Cu{sub 7}O{sub 15-{delta}} (Y-247) has been studied by high-resolution neutron power diffraction. This structure can be described as alternating single CuO chain (123) and double CuO chain (124) blocks. Two fully oxidized polycrystalline Y-247 samples with T{sub c, onset} = 94.8 and 89.3 K, prepared by a sol-gel technique at 1 atm oxygen pressure, were investigated in the temperature range from 5 to 100 K, and the structural changes were determined by Rietveld analysis. The oxygen content was found to be equal in both samples but themore » unit cell parameters and interatomic bond distances differed significantly. The structural changes with temperature in the compound with T{sub c, onset} {approx} 95 K showed that the displacements of the apical oxygen in the 123 and 124 blocks are different. In agreement with the decreased coherence length along the c axis detected by neutron diffraction, electron diffraction. In agreement with the decreased coherence length along the c axis detected by neutron diffraction, electron diffraction studies showed considerable streaking in the sample with T{sub c} = 89 K whereas the sample with T{sub c} = 95 K was more ordered. High-resolution electron microscopy studies indicated that the reason for streaking are stacking faults in the -123-124-123-124-sequence that build the structure.« less
  • Aspects of the growth of decorated stacking faults in a nickel base alloy are investigated by HVEM. The first stages of precipitation occur on perfect loops and that causes their dissociation into outer Frank and inner Shockley partials. Further expansion of Frank loops leads to two types of extrinsic decorated stacking faults. In the first type, the fault is covered with a thin homogeneous layer of precipitate and bounded by sessile dissociated Frank segments. The second type consists of small spherical precipitates spread on the faulted area; in this case, up-climb of the undissociated bounding Frank loop can occasionally bemore » observed.« less
  • In Mg–2 at.% Y–1 at.% Zn alloys, the LPSO (Long Period Stacking Ordered) phase is important to improve mechanical properties of the material. The aim of this paper is to present a study on the phase boundary character in these two-phase alloys. Using EBSD pattern analysis it was found that the 24R structure is the dominant LPSO phase structure in the current alloy. The phase boundary character between the Mg matrix and the LPSO phase was investigated using an improved pseudo-3D EBSD (electron backscatter diffraction) technique in combination with BSE or SE (backscatter or secondary electron) imaging. A large amountmore » of very low-angle phase boundaries was detected. The (0 0 0 2) plane in the Mg matrix which is parallel to the (0 0 0 24) plane in the LPSO phase was found to be the most frequent plane for these phase boundaries. This plane is supposed to be the habit plane of the eutectic co-solidification of the Mg matrix and the LPSO phase. - Highlights: • It is shown that for the investigated alloy the LPSO phase has mainly 24R crystal structure. • A new method is presented which allows accurate determination of the 5-parameter grain or phase boundary character. • It is found that the low-angle phase boundaries appearing in the alloy all have basal phase boundary planes.« less