Microstructural analysis of nickel hydroxide: Anisotropic size versus stacking faults

2005 ◽  
Vol 20 (4) ◽  
pp. 334-344 ◽  
Author(s):  
Montse Casas-Cabanas ◽  
Maria Rosa Palacín ◽  
Juan Rodríguez-Carvajal
Keyword(s):  
Powder Diffraction ◽  
Nickel Hydroxide ◽  
Size Effects ◽  
Microstructural Analysis ◽  
Stacking Faults ◽  
Finite Size ◽  
Line Broadening ◽  
Peak Broadening ◽  
Transmission Electron ◽  
Microstructural Model

Two different approaches for studying sample’s contributions to diffraction-line broadening are analyzed by applying them to several nickel hydroxide samples. Both are based in the refinement of powder diffraction data but differ in the microstructural model used. The first one consists in the refinement of the powder diffraction pattern using the FAULTS program, a modification of DIFFaX, which assigns peak broadening mainly to the presence of stacking faults and treats finite size effects by convolution with a Voigt function. The second method makes use of the program FULLPROF, which allows the use of linear combinations of spherical harmonics to model peak broadening coming from anisotropic size effects. The complementary use of transmission electron microscopy has allowed us to evaluate the best approach for the Ni(OH)2 case. In addition, peak shifts, corresponding to reflections 10l (l≠0) were observed in defective nickel hydroxide samples that can be directly correlated with the degree of faulting.

Classification of stacking faults and their stepwise elimination during the disorder → order transformation of nickel hydroxide

2006 ◽  
Vol 62 (4) ◽  
pp. 530-536 ◽  
Author(s):  
T. N. Ramesh ◽  
P. Vishnu Kamath ◽  
C. Shivakumara
Keyword(s):  
Diffraction Pattern ◽  
Powder Diffraction ◽  
Nickel Hydroxide ◽  
Stacking Faults ◽  
X Ray ◽  
Local Structures ◽  
Different Types ◽  
Different Temperatures ◽  
Stacking Patterns

Nickel hydroxide samples obtained by strong alkali precipitation are replete with stacking faults. The local structures of the stacking faults resemble the stacking patterns of different polytypic modifications that are theoretically possible among the layered hydroxides. This resemblance becomes a basis for the classification of stacking faults into different types. Each type of stacking fault produces a characteristic non-uniform broadening of peaks in the X-ray powder diffraction pattern of nickel hydroxide. DIFFaX simulations aid the classification and quantification of stacking faults. Hydrothermal treatment of a poorly ordered nickel hydroxide slurry at different temperatures (338–473 K) and different durations (5–48 h) shows that the stacking faults are removed in a stepwise manner. The as-precipitated sample has 17–20% stacking faults of the 3R 2 variety, which evolve into the 2H 2 type at 413 K. The 2H 2 stacking faults persist up to 443 K. The stacking faults are completely removed only at 473 K. At this temperature an ordered β-Ni(OH)2 phase is observed.

A correction for anisotropic line broadening due to structural defects in powder diffraction structure analysis

2000 ◽  
Vol 33 (2) ◽  
pp. 338-343 ◽  
Author(s):  
Leonid A. Solovyov
Keyword(s):  
Structure Analysis ◽  
Powder Diffraction ◽  
Structural Defects ◽  
Line Broadening ◽  
Peak Broadening ◽  
Statistical Consideration ◽  
Unit Cells ◽  
Full Profile ◽  
Consistent Information ◽  
Structure Investigations

An anisotropic line-broadening correction allowing for the presence of structural defects in crystals is developed for powder diffraction full-profile structure analysis. The approach is based on the statistical consideration of diffraction from a crystal composed of two types of unit cells differing in atomic arrangement and/or content, but not in shape and size. The correction is incorporated into a computer program for powder diffraction structural analysis. The application of this correction in crystal structure investigations oftrans- and β-trans-[Pd(NH3)2X2] (X= Cl, Br, I) overcame the problem of selective anisotropic peak broadening and allowed precise and self-consistent information about the structure and the microstructure of these compounds to be obtained.

scholarly journals KSm(MoO4)2, an incommensurately modulated and partially disordered scheelite-like structure

2008 ◽  
Vol 64 (2) ◽  
pp. 160-171 ◽  
Author(s):  
Alla Arakcheeva ◽  
Philip Pattison ◽  
Gervais Chapuis ◽  
Marta Rossell ◽  
Andrey Filaretov ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Synchrotron Radiation ◽  
Powder Diffraction ◽  
Rietveld Method ◽  
Cation Ordering ◽  
Powder Diffraction Data ◽  
Line Broadening ◽  
Transmission Electron ◽  
Wave Distribution

The incommensurately modulated scheelite-like KSm(MoO4)2 structure has been refined in the monoclinic superspace group I2/b(αβ0)00 by the Rietveld method on the basis of synchrotron radiation powder diffraction data. The systematic broadening of satellite reflections has been accounted for by applying anisotropic microstrain line-broadening. The microstructure has been studied by transmission electron microscopy (TEM). The partial disorder of the K and Sm cations in the A position is best approximated by a combination of harmonic and complex crenel functions with (0.952Sm + 0.048K) and (0.952K + 0.048Sm) atomic domains. This combination yields a compositional wave distribution from {KMoO4} to {SmMoO4} observed in the ab structure projection along q. The specific features of KSm(MoO4)2 and degree of the A-cation ordering are discussed in comparison with the previously reported structure of KNd(MoO4)2.

A Survey of Diverse Approximations for Microstructural Characterization using Powder Diffraction Data: β-Ni(OH)2, a Case Study

2006 ◽  
Vol 972 ◽  
Author(s):  
Monste Casas-Cabanas ◽  
Juan Rodriguez-Carvajal ◽  
Judith Oro-Sole ◽  
M. Rosa Palacin
Keyword(s):  
Rietveld Refinement ◽  
Microstructural Characterization ◽  
Diffraction Peak ◽  
Powder Diffraction Data ◽  
Line Broadening ◽  
X Ray Diffraction ◽  
X Ray ◽  
Peak Broadening ◽  
Transmission Electron

AbstractThe microstructural features of diverse samples are studied by powder X-ray diffraction using different methods for the analysis of the diffraction peak broadening. The results obtained are thoroughly analyzed taking into account the assumptions and simplifications done in each of the chosen methods (Scherrer, Stokes and Wilson, Williamson-Hall and Rietveld refinement) and direct observation of the studied specimens by transmission electron microscopy is used in order to contrast the results obtained. Classic simple methods that consider only size effects (Scherrer, Stokes and Wilson) or the combined effects of size and strains (Williamson-Hall) provide a rapid overview of the origins of line-broadening but the most reliable results are obtained when the whole diffraction pattern is taken into account (Rietveld refinement).

Microstructural Analysis of SiO2-Al2O3 Glasses

1982 ◽  
Vol 40 ◽  
pp. 562-563
Author(s):  
C. M. Jantzen ◽  
D. G. Howitt
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Microstructural Analysis ◽  
Liquid Immiscibility ◽  
Metastable Region ◽  
Transmission Electron ◽  
Liquidus Temperatures

The mullite-SiO2 liquidus has been extensively studied, and it has been shown that the flattening of the liquidus is related to the existence of a metastable region of liquid immiscibility at sub-liquidus temperatures which is detectable by transmission electron microscopy (TEM) (Fig. 1).

Structure of stacking faults in pyrite using TEM techniques

1992 ◽  
Vol 50 (1) ◽  
pp. 358-359
Author(s):  
Raja Subramanian ◽  
Kenneth S. Vecchio
Keyword(s):  
Lattice Structure ◽  
Stacking Faults ◽  
Covalent Bond ◽  
Group Symmetry ◽  
Iron Pyrite ◽  
Dislocation Glide ◽  
Partial Dislocations ◽  
Transmission Electron ◽  
Contrast Analysis ◽  
Chlorine Ions

The structure of stacking faults and partial dislocations in iron pyrite (FeS2) have been studied using transmission electron microscopy. Pyrite has the NaCl structure in which the sodium ions are replaced by iron and chlorine ions by covalently-bonded pairs of sulfur ions. These sulfur pairs are oriented along the <111> direction. This covalent bond between sulfur atoms is the strongest bond in pyrite with Pa3 space group symmetry. These sulfur pairs are believed to move as a whole during dislocation glide. The lattice structure across these stacking faults is of interest as the presence of these stacking faults has been preliminarily linked to a higher sulfur reactivity in pyrite. Conventional TEM contrast analysis and high resolution lattice imaging of the faulted area in the TEM specimen has been carried out.

Atomic structure of stair rod misfit dislocations at the GaAs on Si(100) interface

1990 ◽  
Vol 48 (4) ◽  
pp. 342-343
Author(s):  
D. Gerthsen
Keyword(s):  
Lattice Constant ◽  
Atomic Structure ◽  
Spherical Aberration ◽  
Stacking Faults ◽  
Misfit Dislocations ◽  
Gaas On Si ◽  
Thermal Expansion Coefficients ◽  
Transmission Electron ◽  
Intersection Line ◽  
Oriented Parallel

The prospect of technical applications has induced a lot of interest in the atomic structure of the GaAs on Si(100) interface and the defects in its vicinity which are often studied by high resolution transmission electron microscopy. The interface structure is determined by the 4.1% lattice constant mismatch between GaAs and Si, the large difference between the thermal expansion coefficients and the polar/nonpolar nature of the GaAs on Si interface. The lattice constant mismatch is compensated by misfit dislocations which are characterized by a/2<110> Burgers vectors b which are oriented parallel or inclined on {111} planes with respect to the interface. Stacking faults are also frequently observed. They are terminated by partial dislocations with b = a/6<112> on {111} planes. In this report, the atomic structure of stair rod misfit dislocations is analysed which are located at the intersection line of two stacking faults at the interface.A very thin, discontinous film of GaAs has been grown by MBE on a Si(100) substrate. Fig.1.a. shows an interface section of a 27 nm wide GaAs island along [110] containing a stair rod dislocation. The image has been taken with a JEOL 2000EX with a spherical aberration constant Cs = 1 mm, a spread of focus Δz = 10 nm and an angle of beam convergence ϑ of 2 mrad.

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]).

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