scholarly journals Non-ambient X-ray and neutron diffraction of novel relaxor ferroelectric xBi2(Zn2/3,Nb1/3)O3–(1 – x)BaTiO3

2021 ◽  
Vol 54 (5) ◽  
Author(s):  
Jessica Marshall ◽  
David Walker ◽  
Pamela Thomas
Keyword(s):  
Neutron Diffraction ◽  
Lattice Parameter ◽  
The Novel ◽  
Temperature Dependent ◽  
Low Loss ◽  
Neutron Data ◽  
Ferroelectric Relaxor ◽  
X Ray ◽  
Unit Cells

The first determination of the phase diagram of the novel ferroelectric relaxor xBi(Zn2/3Nb1/3)O3–(1 − x)BaTiO3 (BZN-BT) has been achieved with a combination of high-resolution X-ray and neutron diffraction up to the miscibility limit near x(BZN) = 20.0% over a temperature range 20 < T < 400 K. The combined X-ray and neutron data show that the instability within the xBZN-(1−x)BT system reaches a maximum at x = 3.9% and is driven by B-site displacement and distortion of the oxygen octahedra in the polar phases. Composition-dependent effects include a narrow Amm2-dominated region focused at x = 3.9%, significant convergence of the lattice parameters in both P4mm and Amm2 phases, and sharp maxima in piezoelectric coefficient d 33 and maximum polarization P max. Lattice parameter dilation at x ≥ 4.0% was observed for both P4mm and Amm2 unit cells, alongside the first appearance of Pm 3 m at 295 K and the onset of significant dielectric relaxation. Low-temperature neutron diffraction indicated a weak or non-existent temperature dependence on the transition from ferroelectric at x = 3.9% to ferroelectric relaxor at x = 4.0%. Temperature-dependent phase transitions were eliminated near x = 3.0%, with the ferroelectric limit observed at x = 5.0% and a transition to a low-loss relaxor dielectric near x = 8.0%.

Unambiguous determination of H-atom positions: comparing results from neutron and high-resolution X-ray crystallography

2010 ◽  
Vol 66 (5) ◽  
pp. 558-567 ◽  
Author(s):  
Anna S. Gardberg ◽  
Alexis Rae Del Castillo ◽  
Kevin L. Weiss ◽  
Flora Meilleur ◽  
Matthew P. Blakeley ◽  
...  
Keyword(s):  
Neutron Diffraction ◽  
Electron Density ◽  
Pyrococcus Furiosus ◽  
X Ray Diffraction ◽  
Neutron Data ◽  
X Ray ◽  
X Ray Crystallography ◽  
Density Maps ◽  
Improved Model

The locations of H atoms in biological structures can be difficult to determine using X-ray diffraction methods. Neutron diffraction offers a relatively greater scattering magnitude from H and D atoms. Here, 1.65 Å resolution neutron diffraction studies of fully perdeuterated and selectively CH3-protonated perdeuterated crystals ofPyrococcus furiosusrubredoxin (D-rubredoxin and HD-rubredoxin, respectively) at room temperature (RT) are described, as well as 1.1 Å resolution X-ray diffraction studies of the same protein at both RT and 100 K. The two techniques are quantitatively compared in terms of their power to directly provide atomic positions for D atoms and analyze the role played by atomic thermal motion by computing the σ level at the D-atom coordinate in simulated-annealing composite D-OMIT maps. It is shown that 1.65 Å resolution RT neutron data for perdeuterated rubredoxin are ∼8 times more likely overall to provide high-confidence positions for D atoms than 1.1 Å resolution X-ray data at 100 K or RT. At or above the 1.0σ level, the joint X-ray/neutron (XN) structures define 342/378 (90%) and 291/365 (80%) of the D-atom positions for D-rubredoxin and HD-rubredoxin, respectively. The X-ray-only 1.1 Å resolution 100 K structures determine only 19/388 (5%) and 8/388 (2%) of the D-atom positions above the 1.0σ level for D-rubredoxin and HD-rubredoxin, respectively. Furthermore, the improved model obtained from joint XN refinement yielded improved electron-density maps, permitting the location of more D atoms than electron-density maps from models refined against X-ray data only.

Determination Of Temperature Dependent Unstressed Lattice Spacings In Crystalline Thin Films On Substrates

1997 ◽  
Vol 505 ◽  
Author(s):  
G. Cornella ◽  
S. Lee ◽  
O. Kraft ◽  
W. D. Nix ◽  
J. C. Bravman
Keyword(s):  
Thin Films ◽  
Thermal Expansion ◽  
Coefficient Of Thermal Expansion ◽  
Strain Analysis ◽  
Lattice Parameter ◽  
Gold Films ◽  
Sample Material ◽  
Temperature Dependent ◽  
X Ray

ABSTRACTX-ray strain analysis via Generalized Focusing Diffractometry (GFD) [1], and the concurrent need for accurate values of the unstrained lattice parameter, are discussed. A new method for determining the unstrained lattice parameter without knowledge of the elastic constants of the sample material is described. Stress measurements at varying temperatures, and extraction of the coefficient of thermal expansion from these measurements, are demonstrated for aluminum and gold films.

scholarly journals Estimating temperature-dependent anisotropic hydrogen displacements with the invariom database and a new segmented rigid-body analysis program

2015 ◽  
Vol 48 (6) ◽  
pp. 1785-1793 ◽  
Author(s):  
Jens Lübben ◽  
Luc J. Bourhis ◽  
Birger Dittrich
Keyword(s):  
High Resolution ◽  
Neutron Diffraction ◽  
Rigid Body ◽  
Analysis Program ◽  
Temperature Dependent ◽  
Neutron Data ◽  
X Ray ◽  
Atomic Displacements ◽  
Atomic Vibrations ◽  
Anisotropic Displacement Parameters

Invariom partitioning and notation are used to estimate anisotropic hydrogen displacements for incorporation in crystallographic refinement models. Optimized structures of the generalized invariom database and their frequency computations provide the information required: frequencies are converted to internal atomic displacements and combined with the results of a TLS (translation–libration–screw) fit of experimental non-hydrogen anisotropic displacement parameters to estimate those of H atoms. Comparison with TLS+ONIOM and neutron diffraction results for four example structures where high-resolution X-ray and neutron data are available show that electron density transferability rules established in the invariom approach are also suitable for streamlining the transfer of atomic vibrations. A new segmented-body TLS analysis program calledAPD-Toolkithas been coded to overcome technical limitations of the established programTHMA. The influence of incorporating hydrogen anisotropic displacement parameters on conventional refinement is assessed.

scholarly journals Lower resolution Laue neutron data yield correct nanocluster formulations

2014 ◽  
Vol 70 (a1) ◽  
pp. C187-C187
Author(s):  
Alison Edwards
Keyword(s):  
Neutron Diffraction ◽  
Single Crystal ◽  
Diffraction Pattern ◽  
Precise Determination ◽  
Data Sets ◽  
X Rays ◽  
Low Resolution ◽  
Neutron Data ◽  
X Ray ◽  
Product Formulation

"The renaissance in Laue studies - at neutron sources - provides us with access to single crystal neutron diffraction data for synthetic compounds without requiring synthesis of prohibitively large amounts of compound or improbably large crystals. Such neutron diffraction studies provide vital data where proof of the presence or absence of hydrogen in particular locations is required and which cannot validly be proved by X-ray studies. Since the commissioning of KOALA at OPAL in 2009[1] we have obtained numerous data sets which demonstrate the vital importance of measuring data even where the extent of the diffraction pattern is at relatively low resolution - especially when compared to that obtainable for the same compound with X-rays. In the Laue experiment performed with a fixed radius detector, data reduction is only feasible for crystals in the ""goldilocks"" zone – where the unit cell is relatively large for the detector, a correspondingly low resolution diffraction pattern in which adjacent spots are less affected by overlap will yield more data against which a structure can be refined than a pattern of higher resolution – one where neighbouring spots overlap rendering both unusable (in our current methodology). Analogous application of powder neutron diffraction in such determinations is also considered. Single crystal neutron diffraction studies of several important compounds (up to 5KDa see figure below)[2] in which precise determination of hydride content by neutron diffraction was pivotal to the final formulation will be presented. The neutron data sets typically possess 20% or fewer unique data at substantially "lower resolution" than the corresponding X-ray data sets. Careful refinement clearly reveals chemical detail which is typically unexplored in related X-ray diffraction studies reporting high profile chemistry despite the synthetic route being one which hydride ought to be considered/excluded in product formulation."

Residual Stresses and Differential Deformation of Electroplated Structures

1989 ◽  
Vol 33 ◽  
pp. 161-169
Author(s):  
G. Sheikh ◽  
I. C. Noyan
Keyword(s):  
Residual Stresses ◽  
Lattice Parameter ◽  
Stress Profile ◽  
X Ray ◽  
Residual Stress Profile ◽  
Cyclic Loading And Unloading ◽  
Nickel Substrates ◽  
Loading And Unloading

AbstractWe report the results of a recent study where nickel substrates electroplated with chromium were loaded in-situ on an x-ray diffractometer. This technique allows determination of lattice spacings in the vicinity of the interface for both the film and the substrate as a function of the applied load. We used such lattice parameter data, SEM observations of the surface and x-ray peak breadth data to study the partitioning of deformation between the film and the substrate. The data indicates progressive loss of adhesion between the film and the substrate with increasing deformation. We observe significant effect of electroplating residual stresses on the mechanical behavior of the system. The loss of adhesion between the film and the substrate coupled with the initial residual stress profile causes an apparent 'negative Poisson's ratio' for the film during initial stages of the loading. This effect disappears with cyclic loading and unloading.

scholarly journals Neutron and X-ray powder diffraction study of skutterudite thermoelectrics

2016 ◽  
Vol 31 (1) ◽  
pp. 16-22
Author(s):  
H. Wang ◽  
M. J. Kirkham ◽  
T. R. Watkins ◽  
E. A. Payzant ◽  
J. R. Salvador ◽  
...  
Keyword(s):  
Neutron Diffraction ◽  
Melt Spinning ◽  
Lattice Parameter ◽  
Type Material ◽  
General Motors ◽  
X Ray Diffraction ◽  
Filling Fraction ◽  
Cubic Symmetry ◽  
X Ray ◽  
P Type

N- and p-type filled-skutterudite materials prepared for thermoelectric power generation modules were analyzed by neutron diffraction at the POWGEN beam line of the Spallation Neutron Source (SNS) and X-ray diffraction (XRD). The skutterudite powders were processed by melt spinning, followed by ball milling and annealing. The n-type material consists of Ba–Yb–Co–Sb and the p-type material consists of Di–Fe–Ni–Sb or Di–Fe–Co–Sb (Di = didymium, an alloy of Pr and Nd). Powders for prototype module fabrication from General Motors and Marlow Industries were analyzed in this study. XRD and neutron diffraction studies confirm that both the n- and p-type materials have cubic symmetry. Structural Rietveld refinements determined the lattice parameters and atomic parameters of the framework and filler atoms. The cage filling fraction was found to depend linearly on the lattice parameter, which in turn depends on the average framework atom size. This knowledge may allow the filling fraction of these skutterudite materials to be purposefully adjusted, thereby tuning the thermoelectric properties.

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