Flux-pinning-related defect structures in melt-processed YBa2Cu3O7-x

1993 ◽  
Vol 51 ◽  
pp. 936-937
Author(s):  
Z. L. Wang ◽  
R. Kontra ◽  
A. Goyal ◽  
D. M. Kroeger ◽  
L.F. Allard
Keyword(s):  
Volume Fraction ◽  
Local Density ◽  
Stacking Faults ◽  
Image Resolution ◽  
Defect Structures ◽  
Atomic Structures ◽  
Transmission Electron ◽  
Point Image ◽  
Related Defect ◽  
Point To Point

Previous studies of Y2BaCuO5/YBa2Cu3O7-δ(Y211/Y123) interfaces in melt-processed and quench-melt-growth processed YBa2Cu3O7-δ using high resolution transmission electron microscopy (HRTEM) and energy dispersive X-ray spectroscopy (EDS) have revealed a high local density of stacking faults in Y123, near the Y211/Y123 interfaces. Calculations made using simple energy considerations suggested that these stacking faults may act as effective flux-pinners and may explain the observations of increased Jc with increasing volume fraction of Y211. The present paper is intended to determine the atomic structures of the observed defects. HRTEM imaging was performed using a Philips CM30 (300 kV) TEM with a point-to-point image resolution of 2.3 Å. Nano-probe EDS analysis was performed using a Philips EM400 TEM/STEM (100 kV) equipped with a field emission gun (FEG), which generated an electron probe of less than 20 Å in diameter.Stacking faults produced by excess single Cu-O layers: Figure 1 shows a HRTEM image of a Y123 film viewed along [100] (or [010]).

Defects in Germanium Nanocrystals Produced by Ion Implantation

2013 ◽  
Vol 709 ◽  
pp. 148-152
Author(s):  
Yu Juan Zhang ◽  
Lei Shang
Keyword(s):  
Electron Microscopy ◽  
Light Emission ◽  
Stacking Faults ◽  
Implantation Dose ◽  
Defect Structures ◽  
High Temperature Annealing ◽  
Planar Defects ◽  
Transmission Electron ◽  
Microstructural Defects ◽  
Germanium Nanocrystals

Germanium nanocrystals (Ge-nc) were produced by the implantation of Ge+ into a SiO2 film deposited on (100) Si, followed by a high-temperature annealing. High-resolution transmission electron microscopy (HRTEM) has been used to investigate the defect structures inside the Ge-nc produced by different implantation doses (1×1016, 2×1016, 4×1016 and 8×1016 cm-2). It has been found that the planar defects such as nanotwins and stacking faults (SFs) are dominant in Ge-nc (60%) for the samples with implantation doses higher than 2×1016 cm-2, while for the sample with an implantation dose lower than 1×1016 cm-2, fewer planar defects are observed in the Ge-nc (20%). The percentages of nanotwins in the planar defects are 87%, 77%, 67% and 60% in four samples, respectively. The twinning structures include single twins, double twins and multiple twins. We also found that there are only SFs in some nanocrystals, and in others the SFs coexist with twins. These microstructural defects are expected to play an important role in the light emission from the Ge-nc.

The Microstructure of “Triple Beam” Ion Irradiated Fe-10% Cr

1981 ◽  
Vol 39 ◽  
pp. 326-327
Author(s):  
L. L. Horton ◽  
J. Bentley ◽  
W. A. Jesser
Keyword(s):  
Volume Fraction ◽  
Computer Code ◽  
Objective Lens ◽  
Defect Structures ◽  
Depth Profiles ◽  
Transmission Electron ◽  
Iron Specimen ◽  
Deposited Energy ◽  
Damage Depth ◽  
Accelerator System

Defect structures which result from fusion environment irradiation of Fe-10%Cr have been studied by transmission electron microscopy (TEM) at 120 kV in a JEM 120C equipped with a special objective lens pole piece for the observation of magnetic materials (AMG). High-purity Fe and Fe-10% Cr disk specimens (3 mm diameter) were bombarded in the ORNL dual Van de Graaff accelerator system at 725, 775, 800, 850, 900, and 950 K. A “triple beam” of He+, D2+, and 4 MeV Fe++ ions was used to achieve 10 dpa with 100 appm He and 410 appm D. In preparing specimens for TEM, the controlled removal or “sectioning” of the damaged region to a predetermined depth was followed by “back-thinning.” A sectioning depth of 0.9 μm was selected, based on the damage-depth profile for a cross section of an electroplated iron specimen (Fig. 1). The maximum cavity volume fraction occurred at ∼1 μm and the maximum dislocation density at ∼1.5 μm. These results do not correspond to the deposited energy and deposited iron depth profiles calculated by the E-DEP-1 computer code.

Atomic Structures and Defects of As-Grown Nb1+αS2 Platelets on Nb Substrates

1992 ◽  
Vol 295 ◽  
Author(s):  
Chuxin Zhou ◽  
L. W. Hobbs
Keyword(s):  
Crystal Structure ◽  
Grain Boundaries ◽  
Diffraction Pattern ◽  
Atomic Structure ◽  
Stacking Faults ◽  
Planar Defect ◽  
Defect Structures ◽  
Planar Defects ◽  
Atomic Structures ◽  
Octahedral Sites

AbstractThe interlocking of Nb1+αS2 platelets developed during sulfidation of Nb results in formation of a compact scale. The atomic structure and defects of these platelets were investigated using HREM. The resulting microstructure is very different from conventional microstructure consisting of polygonal grains and polyhedral grain boundaries because of the anisotropy of the crystal structure. The principal phase was identified as 3R-Nb2+αS2 intergrown with 2H-Nb1+αS2, or with some other arrangement of S-Nb-S slabs. The -S6- octahedral sites between two S-Nb-S slabs provide accommodation for extra Nb or foreign atoms and the large non-stoichiometry of Nb1+αS2. Stacking faults along the c axis account for the high density of planar defect structures observed within almost every platelet. Axial lattice fringe images and streaking in the diffraction pattern indicate that the planar defects are normal to the c direction.

Formation of Defect Structures during Annealing of Cold-deformed L10-ordered equiatomic FePd Intermetallics

2004 ◽  
Vol 842 ◽  
Author(s):  
Anirudha R. Deshpande ◽  
Jörg M.K. Wiezorek
Keyword(s):  
Defect Formation ◽  
Driving Forces ◽  
Cold Deformation ◽  
Stacking Faults ◽  
Formation Mechanisms ◽  
Defect Structures ◽  
Antiphase Boundaries ◽  
Planar Defects ◽  
Fcc Metals ◽  
Transmission Electron

ABSTRACTPlanar defects produced in L10-ordered FePd during annealing after cold-deformation in the disordered cubic state have been characterized by transmission electron microscopy (TEM). The defects evolving during annealing include arrays of overlapping stacking faults (SF's), {111}-conjugated microtwins (μT's) and thermal antiphase boundaries (APB's). The defect formation mechanisms proposed here are similar to twinning mechanism reported for FCC-metals during annealing. Thus, SF arrays and faulted μT's in the L10-ordered FePd appear to form during the early stages of annealing by atomic attachment faulting on {111}-facets of the transformation interfaces. During later stages of annealing the reduced amount and the change in nature of the driving forces for the microstructural rearrangement result in changes in the predominant defect formation mechanism. The features of the defect genesis in L10-FePd are discussed with respect to solid-state transformations during processing of these ferromagnetic intermetallics.

Defect structures of the Cr2O3(11-20) surface: Effect of electron beam irradiation

2021 ◽  
Author(s):  
Wandong Xing ◽  
Haozhi Sha ◽  
Fanyan Meng ◽  
Rong Yu
Keyword(s):  
Electron Microscopy ◽  
First Principles ◽  
Electron Beam Irradiation ◽  
Surface Effect ◽  
Defect Structures ◽  
First Principles Calculations ◽  
Beam Irradiation ◽  
Atomic Structures ◽  
Transmission Electron ◽  
Aberration Corrected

We have revealed the atomic structures and stability of the (11-20) surface of single crystal Cr2O3 combining aberration corrected transmission electron microscopy and first-principles calculations. It is found that the...

High-resolution tem of transformation interfaces in metals

1987 ◽  
Vol 45 ◽  
pp. 284-287
Author(s):  
J. M. Howe
Keyword(s):  
High Resolution ◽  
Physical And Mechanical Properties ◽  
Al Alloys ◽  
Microstructural Development ◽  
Atomic Structures ◽  
Transmission Electron ◽  
High Resolution Tem ◽  
Interphase Boundaries ◽  
Electron Microscopes ◽  
Point To Point

The advent of medium and high-voltage transmission electron microscopes with point-to-point resolutions below 0.2 nm has made it possible to study transformation interfaces in metals at the atomic level. Understanding the atomic structures of these interfaces is critical to understanding microstructural development and the resulting physical and mechanical properties of metals. One area of transformation interfaces in metals that has been investigated by high- resolution transmission electron microscopy (HRTEM), is the structures of interphase boundaries of metastable aging precipitates in Al alloys. The presence of these precipitates is largely responsible for the high strengths of many Al alloys and the low atomic number of Al alloys makes them ideally suited for study by HRTEM. The results from HRTEM Investigations of transformation Interfaces in Al-2%LI-1%Cu and Al-4%Ag alloys which follow, illustrate the wealth of information that HRTEM can provide about transformation interfaces in metals.

The Defect Structures of Fe9S10

1983 ◽  
Vol 31 ◽  
Author(s):  
Thao A. Nguyen ◽  
Linn W. Hobbs
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Stacking Faults ◽  
Defect Structures ◽  
Transmission Electron ◽  
Vacancy Ordering ◽  
Different Types ◽  
Lattice Images ◽  
Antiphase Domains ◽  
Complex Features

ABSTRACTThe defect structures of Fe9S10 have been studied by high-resolution transmission electron microscopy. Lattice images of the 3C and 4C superstructures and at least one other phase, which has not been previously reported, were observed. It has been found that the 4C superstructure transforms into the 3C superstructure rather than the MC phase as previously suggested. Intrinsic stacking faults in the sulfur sublattice and two different types of vacancy-ordering antiphase domains were also observed. Evidence from optical diffratograms of areas containing these defects suggests that complex features in the electron diffraction pattern may be artifactual.

MICROSTRUCTURE AND PROPERTIES OF FERROELECTRIC Bi4Ti3O12 THIN FILMS

1999 ◽  
Vol 13 (26) ◽  
pp. 933-945 ◽  
Author(s):  
B. JIANG ◽  
J. L. PENG ◽  
L. A. BURSILL ◽  
H. WANG
Keyword(s):  
Electron Microscopy ◽  
Thin Films ◽  
Transmission Electron Microscopy ◽  
Defect Structure ◽  
Bismuth Titanate ◽  
Stacking Faults ◽  
Film Morphology ◽  
Defect Structures ◽  
Transmission Electron ◽  
Simulated Images

The film morphology and defect structure of ferroelectric bismuth titanate thin films are studied by high resolution transmission electron microscopy. As-grown and RTA-processed thin films have similar defect structures, consisting of stacking faults and complex intergrowth defect structures. The as-grown specimens prepared at low temperature had smaller particle size with higher density of these defects compared to RTA-processed samples. Detailed atomic structure models for the stacking faults and intergrowth defect structures are proposed and the computer-simulated images are compared with experiment.

Finding the Right Problems: Some HREM Applications to Interfaces

1984 ◽  
Vol 42 ◽  
pp. 376-379
Author(s):  
D. Cherns
Keyword(s):  
Grain Boundaries ◽  
High Resolution Electron Microscopy ◽  
Boundary Structure ◽  
Atomic Structures ◽  
Grain Boundary Structure ◽  
Resolution Electron ◽  
Point To Point ◽  
The Right ◽  
New Generation ◽  
Better Than

The use of high resolution electron microscopy (HREM) to determine the atomic structure of grain boundaries and interfaces is a topic of great current interest. Grain boundary structure has been considered for many years as central to an understanding of the mechanical and transport properties of materials. Some more recent attention has focussed on the atomic structures of metalsemiconductor interfaces which are believed to control electrical properties of contacts. The atomic structures of interfaces in semiconductor or metal multilayers is an area of growing interest for understanding the unusual electrical or mechanical properties which these new materials possess. However, although the point-to-point resolutions of currently available HREMs, ∼2-3Å, appear sufficient to solve many of these problems, few atomic models of grain boundaries and interfaces have been derived. Moreover, with a new generation of 300-400kV instruments promising resolutions in the 1.6-2.0 Å range, and resolutions better than 1.5Å expected from specialist instruments, it is an appropriate time to consider the usefulness of HREM for interface studies.

In situ REM imaging of surface processes on ceramic bulk crystals from 300 to 1670 K in a conventional TEM

1991 ◽  
Vol 49 ◽  
pp. 660-661
Author(s):  
Z. L. Wang ◽  
J. Bentley
Keyword(s):  
High Temperatures ◽  
Image Resolution ◽  
Atomic Processes ◽  
Crystal Surfaces ◽  
Beam Radiation ◽  
Surface Areas ◽  
Transmission Electron ◽  
Reflection Electron Microscopy ◽  
Gas Reactions

Studying the behavior of surfaces at high temperatures is of great importance for understanding the properties of ceramics and associated surface-gas reactions. Atomic processes occurring on bulk crystal surfaces at high temperatures can be recorded by reflection electron microscopy (REM) in a conventional transmission electron microscope (TEM) with relatively high resolution, because REM is especially sensitive to atomic-height steps.Improved REM image resolution with a FEG: Cleaved surfaces of a-alumina (012) exhibit atomic flatness with steps of height about 5 Å, determined by reference to a screw (or near screw) dislocation with a presumed Burgers vector of b = (1/3)<012> (see Fig. 1). Steps of heights less than about 0.8 Å can be clearly resolved only with a field emission gun (FEG) (Fig. 2). The small steps are formed by the surface oscillating between the closely packed O and Al stacking layers. The bands of dark contrast (Fig. 2b) are the result of beam radiation damage to surface areas initially terminated with O ions.

Sign in / Sign up

Export Citation Format

Share Document