Structural imaging of polytypoids in high Tc oxide superconductors

1989 ◽  
Vol 47 ◽  
pp. 156-157
Author(s):  
R. Ramesh ◽  
E. Wang ◽  
J.M. Tarascon ◽  
G. Thomas
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Liquid Nitrogen Temperature ◽  
High Resolution Electron Microscopy ◽  
Oxide Superconductors ◽  
Ion Milling ◽  
Resolution Electron ◽  
The Matrix ◽  
Diffraction Patterns ◽  
Processing Techniques

The structure of the superconducting polytypoid in the newly discovered high Tc super conducting system, Pb2Sr2Cu2Oy has been examined by high resolution electron microscopy, electron diffraction and xray microanalysis. High resolution imaging has shown the presence of the Pb2Sr2Cu2Oy at the grain boundaries. In analogy to the Bi-Ca-Sr-Cu-O(BCSCO)system, it is suggested that this polytypoid could have a lower transition temperature compared to the matrix. This may explain the steps in the resistivity plot. It is also shown that complex cationic ordering, such as replacement of Sr by Ca and/or Y, could lead to extra reflections in the diffraction patterns.Pb-Sr-(Ca-RE)-Cu-O sintered samples were prepared by standard solid state processing techniques. Samples were prepared under 1% flowing oxygen. Samples for electron microscopy were prepared by argon ion milling at liquid nitrogen temperature at 6kV. High resolution electron microscopy was carried out in the Berkeley Atomic Resolution Microscope at 800kV.

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.

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.

Hrem on Grain Boundaries in Oxide Superconductors

1989 ◽  
Vol 156 ◽  
Author(s):  
H.W. Zandbergenl ◽  
G. van Tendeloo
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Grain Boundaries ◽  
Amorphous Material ◽  
High Resolution Electron Microscopy ◽  
Critical Currents ◽  
Polycrystalline Materials ◽  
Oxide Superconductors ◽  
Resolution Electron ◽  
Superconducting Oxides

ABSTRACTHigh resolution electron microscopy has been carried out on grain boundaries in a number of superconducting oxides: YBa2Cu3O77−∂, LaCaBaCu3O7−∂, Bi2Sr2CanCun+1O2n+6+∂, and Pb2(Sr, Ca)3−xAxCu2+nO6+2n+∂. In general no amorphous material or another phase is observed at the grain boundaries. It is argued that the low critical currents in these polycrystalline materials are caused by the atomic structure of (001) interfaces at grain boundaries and concerning YBa2Cu3O7 and LaCaBaCu3O7−∂ by the intercalation of CuO layers starting from the grain boundaries.

On the interpretation of electron diffraction patterns from materials containing planar boundaries: the intergrowth tungsten bronzes

1990 ◽  
Vol 429 (1876) ◽  
pp. 91-117 ◽  
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Electron Diffraction ◽  
High Resolution Electron Microscopy ◽  
Optical Diffraction ◽  
General Interest ◽  
Transmission Electron ◽  
Resolution Electron ◽  
Resolution Imaging ◽  
Diffraction Patterns

Materials containing planar boundaries are of general interest and complete understanding of their structures is important. When direct imaging of the boundaries by, for instance, high-resolution electron microscopy, is impracticable, details of their structure and arrangement may be obtained from electron diffraction patterns. Such patterns are discussed in terms of those from intergrowth tungsten bronzes as specific examples. Fourier-transform calculations for proposed structures have been made to establish, in conjunction with optical-diffraction analogues, the features of the far-field diffraction patterns. These results have been compared with diffraction patterns obtained experimentally by transmission electron microscopy. The aim of the study, to show that the arrangement of the boundaries in these complicated phases can be deduced from their diffraction patterns without the need for high-resolution imaging, has been achieved. The steps to be taken to make these deductions are set out.

Application of the imaging plate to quantitative analysis of electron-diffraction and high-resolution electron microscopy

1989 ◽  
Vol 47 ◽  
pp. 666-667
Author(s):  
K. Hiraga ◽  
D. Shindo ◽  
M. Hirabayashi ◽  
T. Oikawa ◽  
N. Mori ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Quantitative Analysis ◽  
High Resolution ◽  
Electron Diffraction ◽  
Electron Micrographs ◽  
High Resolution Electron Microscopy ◽  
Imaging Plate ◽  
Resolution Electron ◽  
Diffraction Patterns ◽  
High Resolution Electron Micrographs

The “Imaging Plate” (IP) has three superior characteristics, i.e., high sensitivity to the electron beam, and a wide dynamic range and good linearity for electron dose compared with conventional EM films. The use of the IP is expected to lead to quantitative analysis of electron microscopy. The purpose of the present work is to examine the possibility of application of the IP to the quantitative analysis of electron diffraction and high-resolution electron microscopy.By using the TEM-IP System developed by Oikawa et al., which is published in this conference, electron diffraction patterns and high-resolution electron micrographs taken on the IP with an effective size of 102 х 77 mm2 were convertedinto digital data of 2048 х 1536 pixels with 4096 gray levels. Observations of electron diffraction patterns and high-resolution electron micrographs were made with a 200 kV (JEM-2000FX) and a 400 kV (JEM-4000EX) electron microscope, respectively.

Ordered Structures in Gd2CuO4 and isostructural cuprates

1989 ◽  
Vol 47 ◽  
pp. 160-161
Author(s):  
T. E. Mitchell ◽  
T. Roy ◽  
Z. Fisk ◽  
S-W Cheong ◽  
J. D. Thompson ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Single Crystals ◽  
Liquid Nitrogen ◽  
High Resolution Electron Microscopy ◽  
Ion Milling ◽  
Ordered Structures ◽  
Resolution Electron

INTRODUCTION.The lanthanide cuprates Ln2CuO4 (Ln = Pr, Nd, Eu, Gd, etc.), have a a triple perovskite unit cell.The structure is tetragonal, 14/mmm, a ∼ 0.39nm, c ∼1.19nm, with layered nets of [CuO4] squares. By contrast, the structure of La2CuO4, which also has a triple perovskite cell, contains layers of [CuO6] octahedra. La2CuO4 becomes superconducting by doping with SrO while Ln2CuO4 becomes superconducting by doping with CeO2 for Ln = Pr, Nd and Sm. Both La2CuO4 and YBa2Cu3O7 have a tetragonal-to-orthorhombic transformation while Ln2CuO4 remains tetragonal.The present study was undertaken to investigate microstructures in the lanthanide cuprates.EXPERIMENTAL. The Ln2CuO4 single crystals were grown as plates from a PbO or CuO flux. Specimens for TEM were prepared by ion milling using a liquid nitrogen specimen cooler. High resolution electron microscopy (HREM) was performed on either a Philips CM3OST at 300kV or a JEM4000FX at 400kV.

Characterization of Dislocations and Interfaces in Semiconductors by High Resolution Electron Microscopy

1980 ◽  
Vol 2 ◽  
Author(s):  
J.C.H. Spence ◽  
A. Olsen
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
High Resolution Electron Microscopy ◽  
Local Symmetry ◽  
Partial Dislocations ◽  
Resolution Electron ◽  
Lattice Images ◽  
Diffraction Patterns ◽  
The Individual

ABSTRACTIt is not presently possible to resolve the individual atoms in any semiconductor by high resolution electron microscopy (HREM). However symmetry arguments may be used to allow near-atomic resolution lattice images to be interpreted in rare favorable cases. This method is applied to the problem of distinguishing shuffle and glide set partial dislocations in silicon. It is also proposed that two dimensional characteristic loss energy selected diffraction patterns be used to reveal the local symmetry about selected substitutional species implanted in semiconductor lattices.

Effect of One-Step and Two-Step Aging Treatments on Microstructure and Properties of an Al-9.0Zn-2.0Mg-2.0Cu Alloy

2018 ◽  
Vol 941 ◽  
pp. 949-954 ◽  
Author(s):  
Kai Wen ◽  
Bai Qing Xiong ◽  
Yong An Zhang ◽  
Zhi Hui Li ◽  
Xi Wu Li ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Aging Treatment ◽  
High Strength ◽  
High Resolution Electron Microscopy ◽  
Slow Increase ◽  
Microstructure Observation ◽  
Resolution Electron ◽  
The Matrix ◽  
One Step ◽  
Diffraction Patterns

Aging treatments of an Al-9.0Zn-2.0Mg-2.0Cu alloy, which belongs to high strength aluminum alloy widely used in aerospace industry, are investigated by various techniques, including hardness, electrical conductivity, mechanical properties, transmission electron microscopy (TEM) and high-resolution electron microscopy (HREM). The result shows that hardness and conductivity for one-step aging treatment increase with aging time prolongs while those for two-step aging treatment exhibit increment and decrement, respectively. Besides, the ultimate tensile strength (UTS) and yield strength (YS) for one-step and two-step aging treatments show slow increase and obvious decrease, respectively. Based on these, typical T6 and T76 aging regimes are extracted for microstructure observation. The matrix precipitates for the T6 alloy have small size and dispersive distribution while that for the T76 alloy has big size and sparse distribution. The grain boundary precipitates for both exhibit discontinuous distribution and the T76 alloy has larger size and broader precipitate free zones. The selected area diffraction patterns and HREM observations reveal that main precipitates for the T6 alloy are GPI zone, GPII zone and η' phase while for the T76 alloy are η' phase and η phase.

Plan-view microstructures of Co/Ru bilayers

1995 ◽  
Vol 10 (6) ◽  
pp. 1539-1545 ◽  
Author(s):  
G.Z. Pan ◽  
A. Michel ◽  
V. Pierron-Bohnes ◽  
P. Vennéguès ◽  
M.C. Cadeville
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Electron Diffraction ◽  
High Resolution Electron Microscopy ◽  
Image Contrast ◽  
Misfit Dislocations ◽  
Double Diffraction ◽  
Plan View ◽  
Resolution Electron ◽  
Diffraction Patterns

Plan-view microstructures of two Co/Ru bilayers with a composition of [Co12ÅRu45Å]2 and [Co40ÅRu35Å]2 have been studied by conventional and high resolution electron microscopy. Large differences in electron diffraction and image contrast between the two bilayers were observed, which are recognized as the microstructural variations during the relaxation of large coherent planar strains when the Co layers wet coherently or semicoherently the Ru layers. For the [Co12ÅRu45Å]2 bilayer, the Co layers are unrelaxed from the Ru layers; only one set of electron diffraction patterns was observed, and the image consists of three types of contrasts which are closely related with either the generation and movement of misfit dislocations or large coherent strains. For the [Co40ÅRu35Å]2 bilayer, the Co layers are relaxed basically from the Ru layers; two sets of electron diffraction patterns with double diffraction spots were observed, and the image consists of small irregular areas with moiré fringe dots.

Metastable Precipitates and their Misfit Strains in a Cu-0.9wt%Be Single Crystal

2007 ◽  
Vol 561-565 ◽  
pp. 2297-2300 ◽  
Author(s):  
Ryoichi Monzen ◽  
Toshiro Sakai ◽  
Chihiro Watanabe
Keyword(s):  
Electron Microscopy ◽  
Phase Transformation ◽  
High Resolution ◽  
Single Crystal ◽  
High Resolution Electron Microscopy ◽  
Length Change ◽  
Misfit Dislocations ◽  
Absolute Value ◽  
Resolution Electron ◽  
The Matrix

The precipitation processes from G.P. zones to γ’ in a Cu−0.9wt%Be alloy single crystal containing only the G.P. zones parallel to the matrix (001)α plane are investigated by high-resolution electron microscopy. The precipitate phases follow a G.P. zone → γ” → γI + γ’ sequence. The G.P. zone to γI phase transformation occurs successively via γ” during aging, while the γ’ phase heterogeneously precipitates on the γI phase. From length-change measurements during aging, the misfit strains of γ’ precipitates in directions perpendicular and parallel to [001]α are estimated as ε11 =ε22 = −0.03 and ε33 = −0.09, respectively. The observation that the estimated absolute value of ε33 is much smaller than that of ε33 = −0.25 calculated using lattice parameters of the γ’ phase and Cu matrix is understood in terms of the relaxation of ε33 by interfacial misfit dislocations.

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