Rietveld Analysis and Pair Wise Substitutional Alloys

1991 ◽  
Vol 35 (A) ◽  
pp. 63-68
Author(s):  
Wayne D. Kaplan ◽  
Giora Kimmel
Keyword(s):  
Solid Solution ◽  
Rare Earth ◽  
Powder Diffraction ◽  
Rietveld Analysis ◽  
Comprehensive Model ◽  
Powder Diffraction Data ◽  
Unique Role ◽  
X Ray ◽  
Substitutional Alloys

AbstractRietveld Analysis on X-Ray powder diffraction data was used to build a comprehensive model of the structures in gallmm rich R-Ga systems (R is a rare earth between La and Gd). The ability to refine occupation factors as well as atomic positions allowed for the analysis of the e solid solution, its structural relation to the ordered ∊′ phase, and the unique role of the Ga-Ga pairs in these systems.

X-RAY DIFFRACTION STUDY ON THE CRYSTAL STRUCTURE OF Sm1+xBa2−xCu3O7−y

1988 ◽  
Vol 02 (02) ◽  
pp. 583-588 ◽  
Author(s):  
H. ASANO ◽  
Y. YOKOYAMA ◽  
M. NISHINO ◽  
H. KATOH ◽  
H. AKINAGA ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Solid Solution ◽  
Diffraction Study ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Rietveld Analysis ◽  
Powder Diffraction Data ◽  
X Ray Diffraction ◽  
X Ray ◽  
Structure Changes

Crystal structures in solid solution of Sm 1+x Ba 2−x Cu 3 O 7−y (X = 0 - 0.4) have been investigated by Rietveld analysis of X-ray powder diffraction data. The structure changes from orthorhombic to tetragonal at x=0.2. With the increase of x, Tc decreases monotonically from 90 K and the compound becomes semiconducting at x=0.4.

scholarly journals Role of chemical substitution in the photoluminescence properties of cerium samarium tungstates Ce(2-x)Smx (WO4)3 (0≤x≤0.3)

2020 ◽  
Vol 225 ◽  
pp. 01013
Author(s):  
K. Derraji ◽  
C. Favotto ◽  
J-C Valmalette ◽  
S. Villain ◽  
J-R. Gavarri ◽  
...  
Keyword(s):  
Solid Solution ◽  
Rietveld Analysis ◽  
Excitation Energies ◽  
Diffraction Profile ◽  
Vacancy Defects ◽  
X Ray ◽  
Cell Parameters ◽  
Structural Distortions ◽  
Ir Emission

In the general framework of the development of materials with tunable photoluminescence, a series of cerium samarium tungstates Ce(2-x)Smx(WO4)3 with x≤0.3 was synthesized by a coprecipitation method followed by thermal treatment at 1000 °C. The polycrystalline compounds were characterized by X-ray diffraction, scanning electron microscopy and photoluminescence experiments. In the present work, the objective would be to determine the role of PL emitting centers in the variations of PL intensities. Firstly, Rietveld analysis showed a decrease of cell parameters and confirmed that a solid solution was obtained. Diffraction profile analyses showed that structural distortions increasing with composition x were observed: they were ascribed to difference in cation sizes of Ce3+ and Sm3+, and to defects generated during crystal growth. The photoluminescence (PL) spectra were obtained under X-Ray (45 kV-35 mA) and UV (364.5 nm) excitations. Two PL emissions of Ce3+ were observed only under UV excitation. Four PL emissions of Sm3+ were observed under UV and X-ray excitations, and their intensities decreased with increasing composition x. Two additional transitions were observed under UV and X-ray excitations: they were attributed to oxygen vacancy defects. In the range 800 to 1000 nm, an increasing IR emission is observed: it was ascribed to emissions due to other oxygen vacancies. The main results are reported in Table 1. The chromaticity diagram (see Figure 1) showed that the colors associated with PL responses vary with Sm composition and excitation energies. This offers the opportunity to develop materials with tunable PL. To better understand this complex behavior, now, we plan to study the solid solution in the composition range x>0.3.

scholarly journals Quantitative Phase Analysis of Skarn Rocks by the Rietveld Method Using X-ray Powder Diffraction Data

Minerals ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 894
Author(s):  
Yana Tzvetanova ◽  
Ognyan Petrov ◽  
Thomas Kerestedjian ◽  
Mihail Tarassov
Keyword(s):  
Powder Diffraction ◽  
Diffraction Data ◽  
Rietveld Method ◽  
Rietveld Analysis ◽  
Quantitative Phase Analysis ◽  
Chemical Compositions ◽  
Powder Diffraction Data ◽  
X Ray ◽  
Fine Grained ◽  
Variable Chemical

The Rietveld method using X-ray powder diffraction data was applied to selected skarn samples for quantitative determination of the present minerals. The specimens include garnet, clinopyroxene–garnet, plagioclase–clinopyroxene–wollastonite–garnet, plagioclase–clinopyroxene–wollastonite, plagioclase–clinopyroxene–wollastonite–epidote, and plagioclase–clinopyroxene skarns. The rocks are coarse- to fine-grained and characterized by an uneven distribution of the constituent minerals. The traditional methods for quantitative analysis (point-counting and norm calculations) are not applicable for such inhomogeneous samples containing minerals with highly variable chemical compositions. Up to eight individual mineral phases have been measured in each sample. To obtain the mineral quantities in the skarn rocks preliminary optical microscopy and chemical investigation by electron probe microanalysis (EPMA) were performed for the identification of some starting components for the Rietveld analysis and to make comparison with the Rietveld X-ray powder diffraction results. All of the refinements are acceptable, as can be judged by the standard indices of agreement and by the visual fits of the observed and calculated diffraction profiles. A good correlation between the refined mineral compositions and the data of the EPMA measurements was achieved.

Update in a Rietveld analysis program for x-ray powder spectro-diffractometry

2003 ◽  
Vol 18 (1) ◽  
pp. 32-35 ◽  
Author(s):  
Yanan Xiao ◽  
Fujio Izumi ◽  
Timothy Graber ◽  
P. James Viccaro ◽  
Dale E. Wittmer
Keyword(s):  
Computer Program ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Rietveld Analysis ◽  
Anomalous Scattering ◽  
Analysis Program ◽  
Powder Diffraction Data ◽  
X Ray ◽  
Synchrotron Light ◽  
Diffraction Patterns

A computer program for refining anomalous scattering factors using x-ray powder diffraction data was revised on the basis of the latest version of a versatile pattern-fitting system, RIETAN-2000. The effectiveness of the resulting program was confirmed by applying it to simulated and measured powder-diffraction patterns of Mn3O4 taken at a synchrotron light source.

Element-selective charge density visualization of endohedral metallofullerenes using synchrotron X-ray multi-wavelength anomalous powder diffraction data

2013 ◽  
Vol 46 (3) ◽  
pp. 649-655 ◽  
Author(s):  
Sachiko Maki ◽  
Eiji Nishibori ◽  
Daisuke Kawaguchi ◽  
Makoto Sakata ◽  
Masaki Takata ◽  
...  
Keyword(s):  
Charge Density ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Rietveld Analysis ◽  
Entropy Method ◽  
Powder Diffraction Data ◽  
X Ray ◽  
Density Maps ◽  
Medium Resolution ◽  
Multi Wavelength

An algorithm for determining the element-selective charge density has been developed using the maximum entropy method (MEM), Rietveld analysis and synchrotron X-ray multi-wavelength anomalous powder diffraction data. This article describes in detail both experimental and analytical aspects of the developed method. A structural study of yttrium mono-metallofullerene, Y@C82, 1:1 co-crystallized with toluene using the present technique is reported in order to demonstrate the applicability of the method even when only medium resolution data are available (d> 1.32 Å). Element-selective MEM charge density maps, computed from synchrotron X-ray powder diffraction data collected at three distinct wavelengths around the yttriumK-absorption edge (∼0.727 A), are employed for determining three crystallographic sites of the disordered yttrium.

scholarly journals RbCa2Nb3O10from X-ray powder data

2009 ◽  
Vol 65 (6) ◽  
pp. i44-i44 ◽  
Author(s):  
Zhen-Hua Liang ◽  
Kai-Bin Tang ◽  
Qian-Wang Chen ◽  
Hua-Gui Zheng
Keyword(s):  
Crystal Structure ◽  
Solid State ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Solid State Reaction ◽  
Perovskite Structure ◽  
Three Dimensional ◽  
Rietveld Analysis ◽  
Powder Diffraction Data ◽  
X Ray

Rubidium dicalcium triniobate(V), RbCa2Nb3O10, has been synthesized by solid-state reaction and its crystal structure refined from X-ray powder diffraction data using Rietveld analysis. The compound is a three-layer perovskite Dion–Jacobson phase with the perovskite-like slabs derived by termination of the three-dimensional CaNbO3perovskite structure along theabplane. The rubidium ions (4/mmmsymmetry) are located in the interstitial space.

scholarly journals Structural Chemistry of Some Phases in The YC-Ni-B System

1994 ◽  
Vol 376 ◽  
Author(s):  
B. C. Chakoumakos
Keyword(s):  
Powder Diffraction ◽  
Single Phase ◽  
Rietveld Analysis ◽  
Neutron Powder Diffraction ◽  
The Other ◽  
Powder Diffraction Data ◽  
X Ray ◽  
Neutron Powder Diffraction Data ◽  
Arc Melting ◽  
Phase Pure

ABSTRACTNiB, monoclinic Ni4B3, Ni2B and Ni3B were prepared by arc-melting and their roomtemperature crystal structures were refined by Rietveld analysis of neutron powder diffraction data. The NiB refinement is altogether new data. Although the B atoms in NiB form characteristic zigzag chains, the primary coordination of each atom by atoms of the other kind is similar and distinctively sevenfold, with one short (2.117 Å), two intermediate (2.152 Å), and four long (2.163 Å) bonds. Other samples with stoichiometries (YC)nNi2B2, n = 3, 4, did not yield single-phase material, but both x-ray and neutron powder diffraction suggest that the n = 4 structure is present in both of these samples. Phase-pure samples of these homologues may require non-stoichiometry and a more controlled thermal history than is attainable by arc melting.

Drastic Decrease of the Curie Temperature in the Solid Solution GdRuxCd1–x

2009 ◽  
Vol 64 (3) ◽  
pp. 356-360 ◽  
Author(s):  
Frank Tappe ◽  
Falko M. Schappacher ◽  
Wilfried Hermes ◽  
Matthias Eul ◽  
Rainer Pöttgen
Keyword(s):  
Solid Solution ◽  
Magnetic Properties ◽  
Curie Temperature ◽  
Powder Diffraction ◽  
Solid Solutions ◽  
Induction Melting ◽  
Powder Diffraction Data ◽  
X Ray ◽  
Drastic Effect ◽  
Cscl Structure

Five samples of solid solutions GdRuxCd1−x extending up to x ≈ 0.25 were synthesized by induction-melting of the elements in sealed tantalum tubes. According to X-ray powder diffraction data, the GdRuxCd1−x samples crystallize with the cubic CsCl structure. The structures of two crystals were refined from diffractometer data: Pm3̄m, a = 372.41(4) pm, wR2 = 0.0363, 45 F2, 5 variables for GdRu0.10(1)Cd0.90(1) and a = 367.70(4) pm, wR2 = 0.0301, 39 F2, 5 variables for GdRu0.20(1)Cd0.80(1). The cadmium-ruthenium substitution has a drastic effect on the magnetic properties. All samples order ferromagnetically, however, the Curie temperature decreases drastically from 258 K for GdCd to 63.6 K for GdRu0.20Cd0.80 with a Vegard-type behavior.

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