Order and disorder in NMC layered materials: a FAULTS simulation analysis

The program FAULTS has been used to simulate the X-ray powder diffraction (XRD), neutron powder diffraction (NPD), and electron diffraction (ED) patterns of several structural models for LiNi1/3Mn1/3Co1/3O2, including different types of ordering of the transition metal (TM) cations in the TM slabs, different amounts of Li+/NiII+ cation mixing and different amounts of stacking faults. The results demonstrate the relevance of the structural information provided by NPD and ED data as compared with XRD to characterize the microstructure of NMC (LiNi1−y-zMnyCozO2) compounds.

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

Acta Crystallographica Section B Structural Science ◽

10.1107/s0108768106013188 ◽

2006 ◽

Vol 62 (4) ◽

pp. 530-536 ◽

Cited By ~ 26

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.

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Crystal structure solution for the A 6 B 2O17 (A = Zr, Hf; B = Nb, Ta) superstructure

Acta Crystallographica Section B Structural Science Crystal Engineering and Materials ◽

10.1107/s2052520619001963 ◽

2019 ◽

Vol 75 (2) ◽

pp. 227-234 ◽

Cited By ~ 4

Author(s):

Scott J. McCormack ◽

Waltraud M. Kriven

Keyword(s):

Crystal Structure ◽

Powder Diffraction ◽

Neutron Powder Diffraction ◽

X Ray ◽

Order And Disorder ◽

Solid Solution Range ◽

Structure Solution ◽

Compositional Variations ◽

Structural Mechanisms

Zr6Ta2O17, Hf6Nb2O17 and Hf6Ta2O17 crystal structure solutions have been solved using synchrotron X-ray powder diffraction and neutron powder diffraction in conjunction with simulated annealing, charge flipping and Rietveld refinement. These structures have been shown to be isomorphous with the Zr6Nb2O17 superstructure, leading to the classification of the A 6 B 2O17 (A = Zr, Hf; B = Nb, Ta) orthorhombic compound family with symmetry Ima2 (No. 46). The asymmetrical structural units of cation-centred oxygen polyhedra used to build the structure are as follows: (i) one set of symmetry-equivalent six-coordinated polyhedra, (ii) three sets of symmetry-equivalent seven-coordinated polyhedra and (iii) one set of symmetry-equivalent eight-coordinated polyhedra. The potential for cation order and disorder was discussed in terms of cation atomic number contrast in X-ray and neutron powder diffraction as well as the bond valence method. In addition, the structural mechanisms for experimentally observed compositional variations within the solid solution range can be attributed to the addition or removal of a set of symmetry-equivalent seven-coordinated polyhedra accompanied by corresponding oxygen tilts within the A 6 B 2O17 structure.

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Influence of planar defects on powder diffractograms of fcc metals

Powder Diffraction ◽

10.1154/1.1523080 ◽

2002 ◽

Vol 17 (4) ◽

pp. 270-277 ◽

Cited By ~ 10

Author(s):

A. I. Ustinov ◽

N. M. Budarina

Keyword(s):

Powder Diffraction ◽

Stacking Faults ◽

Diffraction Peak ◽

High Concentration ◽

Planar Defects ◽

X Ray ◽

Fcc Metals ◽

Different Types ◽

High Degree ◽

Kinematic Approach

X-ray powder diffractograms from fcc crystals containing high concentration (more than 1%) of planar defects [deformation stacking faults (SF), double deformation SF, twin boundaries (TB)] have been simulated by Monte Carlo method in kinematic approach. It was shown that the characteristics of powder diffraction peak profiles (except peaks with indexes H00) dependent nonmonotonically on PD concentration, during which peak maximums stay in Bragg positions. An addition point to emphasize is that an appearance of TB only in the crystal not affects on position of all peaks. Several types of PD to be occurred simultaneously in the crystal influence on powder diffractograms additively. Peculiarities of the powder diffraction pattern inherent in different types of PD have been revealed to permit predominant PD type to be found with a high degree of accuracy based on experimental data.

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