X-ray powder diffraction study of K2MSiO4, M=Mg, Zn, Co, Cd

1996 ◽  
Vol 11 (1) ◽  
pp. 51-55 ◽  
Author(s):  
W. A. Dollase
Keyword(s):  
Powder Diffraction ◽  
Diffraction Data ◽  
Rietveld Method ◽  
Site Occupancy ◽  
Cubic Phase ◽  
Variable Degree ◽  
Cubic Symmetry ◽  
X Ray ◽  
Constrained Model ◽  
Diffraction Patterns

The title materials are stuffed cristobalites possessing moderate to extreme pseudosymmetry. On the bases of their X-ray powder diffraction patterns, the Mg, Zn, and Cd compounds had been previously reported as cubic and, more recently, the Zn phase as orthorhombic. Newly measured X-ray powder diffraction data demonstrate that all (including the hitherto unknown Co analog) have the Pca21 structure of Na2BeSiO4 at room temperature, but with a widely variable degree of cubic pseudosymmetry. Observed X-ray diffraction data are in good agreement with those calculated by the Rietveld method using a constrained model with Pca21 M2+/Si site occupancy and pseudocentrosymmetric Pcab atom locations. For the most nearly cubic phase, the Cd compound, there is too little deviation in the pattern from cubic symmetry to support atom coordinate refinement even with the constrained model. In these derivatives of the stuffed cristobalite structure family, M2+ and Si atoms form an ordered tetrahedral array which avoids M2+–O–M2+ connections. Potassium atoms fill all of the intervening large cavity sites.

X-Ray Powder Diffraction Data and Crystal Refinement of a New Compound AlCrNi3Pr

2016 ◽  
Vol 850 ◽  
pp. 3-7
Author(s):  
Shu Hui Liu ◽  
Liu Qing Liang ◽  
Chang Sheng Qin ◽  
De Gui Li ◽  
Ling Min Zeng ◽  
...  
Keyword(s):  
Powder Diffraction ◽  
Diffraction Data ◽  
Rietveld Method ◽  
Structure Refinement ◽  
Structure Type ◽  
Hexagonal Structure ◽  
Powder Diffraction Data ◽  
Tungsten Electrode ◽  
X Ray ◽  
Diffraction Patterns

Rare earth-transition metal (R-T) intermetallics have been well used because of their excellent properties. The X-ray diffraction patterns of many new phases in the R-T system have not been extensively studied. A new compound AlCrNi3Pr was prepared by arc melting using non-consumable tungsten electrode under argon atmosphere, and then annealed at 1023K for 30 days. The X-ray powder diffraction data of AlCrNi3Pr was collected on a Rigaku SmartLab X-ray powder diffractometer. The powder patterns of the compound were indexed, and the structure refinement by using Rietveld method indicated that the AlCrNi3Pr compound crystallized in the hexagonal structure, space group P6/mmm (No.191) with PrNi5 structure type, a=b=5.0553(9) Ǻ, c=4.0763(6) Ǻ, V=90.22Ǻ3, Z=1, ρx=7.288g cm-3, the Smith–Snyder FOM F30=279.1(0.0044, 32) and the intensity ratio RIR=1.23.

Synthesis and Rietveld refinement of skutterudite-related phase CoSn1.5Te1.5

2008 ◽  
Vol 23 (1) ◽  
pp. 15-19 ◽  
Author(s):  
F. Laufek ◽  
J. Návrátil ◽  
V. Goliáš
Keyword(s):  
Crystal Structure ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Title Compound ◽  
Rietveld Method ◽  
Powder Diffraction Data ◽  
Cubic Symmetry ◽  
X Ray ◽  
Long Range Ordering ◽  
Related Phase

Crystal structure of the skutterudite-related phase has been refined by the Rietveld method from X-ray powder diffraction data. Refined crystallographic data for CoSn1.5Te1.5 are a=12.9063(2) Å, c=15.7837(3) Å, V=2276.89(4) Å3, space group R3 (No. 148), Z=24, and Dx=7.50 g/cm3. The crystal structure of the title compound can be viewed as a modification of the skutterudite structure (CoAs3)—it is isostructural with CoGe1.5Te1.5 and IrSn1.5Te1.5. In the structure of CoSn1.5Te1.5, the Sn and Te atoms exhibit long-range ordering, which results in lowering of the original cubic symmetry of the skutterudite structure to the trigonal one.

Crystallographic study of ternary ordered skutterudite IrGe1.5Se1.5

2010 ◽  
Vol 25 (3) ◽  
pp. 247-252 ◽  
Author(s):  
F. Laufek ◽  
J. Návrátil
Keyword(s):  
Crystal Structure ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Rietveld Method ◽  
Crystallographic Data ◽  
Powder Diffraction Data ◽  
X Ray ◽  
Crystallographic Study ◽  
Related Phase ◽  
The Ideal

The crystal structure of skutterudite-related phase IrGe1.5Se1.5 has been refined by the Rietveld method from laboratory X-ray powder diffraction data. Refined crystallographic data for IrGe1.5Se1.5 are a=12.0890(2) Å, c=14.8796(3) Å, V=1883.23(6) Å3, space group R3 (No. 148), Z=24, and Dc=8.87 g/cm3. Its crystal structure can be derived from the ideal skutterudite structure (CoAs3), where Se and Ge atoms are ordered in layers perpendicular to the [111] direction of the original skutterudite cell. Weak distortions of the anion and cation sublattices were also observed.

Rietveld Refinement of the BaTiO3 from X-Ray Powder Diffraction

2009 ◽  
Vol 79-82 ◽  
pp. 593-596
Author(s):  
Feng Sun ◽  
Yan Sheng Yin
Keyword(s):  
Rietveld Refinement ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Rietveld Method ◽  
Structural Parameters ◽  
Ferroelectric Ceramic ◽  
Powder Diffraction Data ◽  
Ceramic Powders ◽  
Space Group ◽  
X Ray

The ferroelectric ceramic BaTiO3 was synthesized at 1000 °C for 5 h. The structure of the system under study was refined on the basis of X-ray powder diffraction data using the Rietveld method. The system crystallizes in the space group P4mm（99）. The refinement of instrumental and structural parameters led to reliable values for the Rp, Rwp and Rexp.We use the TOPAS software of Bruker AXS to refine this ceramic powders and show its conformation

Structure Refinements of the Layered Intergrowth Phases SbIIISbV x A 1−x TiO6 (x≃0, A = Ta, Nb) Using Synchrotron X-ray Powder Diffraction Data

1997 ◽  
Vol 53 (6) ◽  
pp. 861-869 ◽  
Author(s):  
C. D. Ling ◽  
J. G. Thompson ◽  
S. Schmid ◽  
D. J. Cookson ◽  
R. L. Withers
Keyword(s):  
Single Crystal ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Homologous Series ◽  
Rietveld Method ◽  
Powder Diffraction Data ◽  
X Ray Diffraction ◽  
Synchrotron Source ◽  
X Ray ◽  
The Family

The structures of the layered intergrowth phases SbIIISb^{\rm V}_xAl-xTiO6 (x \simeq 0, A = Ta, Nb) have been refined by the Rietveld method, using X-ray diffraction data obtained using a synchrotron source. The starting models for these structures were derived from those of Sb^{\rm III}_3Sb^{\rm V}_xA 3−xTiO14 (x = 1.26, A = Ta and x = 0.89, A = Nb), previously solved by single-crystal X-ray diffraction. There were no significant differences between the derived models and the final structures, validating the approach used to obtain the models and confirming that the n = 1 and n = 3 members of the family, Sb^{\rm III}_nSb^{\rm V}_xA n−xTiO4n+2 are part of a structurally homologous series.

The X-Ray Powder Diffraction Patterns and Crystal Structure for Al2M3Y(M=Cu, Ni)

2014 ◽  
Vol 950 ◽  
pp. 48-52
Author(s):  
De Gui Li ◽  
Ming Qin ◽  
Liu Qing Liang ◽  
Zhao Lu ◽  
Shu Hui Liu ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Hexagonal Structure ◽  
Argon Atmosphere ◽  
X Ray Diffraction ◽  
High Quality ◽  
X Ray ◽  
Arc Melting ◽  
Diffraction Patterns

The Al2M3Y(M=Cu, Ni) compound was synthesized by arc melting under argon atmosphere. The high-quality powder X-ray diffraction data of Al2M3Y have been presented. The refinement of the X-ray diffraction patterns for the Al2M3Y compound show that the Al2M3Y has hexagonal structure, space groupP6/mmm(No.191), with a = b = 5.1618(2) Å, c = 4.1434(1) Å,V= 95.6 Å3,Z= 1,ڑx= 5.7922 g/cm3,F30= 155.5(0.0057, 34), RIR = 2.31 for Al2Cu3Y, and with a = b = 5.0399(1) Å, c = 4.0726(1) Å,V= 89.59 Å3,Z= 1,ڑx= 5.9118 g/cm3,F30= 135.7(0.0072, 30), RIR = 2.54 for Al2Ni3Y.

scholarly journals Pressing the Limits of Rietveld Refinement

1988 ◽  
Vol 41 (2) ◽  
pp. 297 ◽  
Author(s):  
RA Young
Keyword(s):  
Powder Diffraction ◽  
Diffraction Data ◽  
Structure Refinement ◽  
Site Occupancy ◽  
The Other ◽  
Powder Diffraction Data ◽  
X Ray ◽  
Neutron Powder Diffraction Data ◽  
Refinement Method

Two examples are given, one with X-ray data and one with netltron data, of the determination of structural detail which appear to be at the edge of current possibility for the Rietveld structure-refinement method. In the first example, 2�2 wt% Sb substituted in CalO(P04)6F2 was located. X-ray powder diffraction data collected with special attention to intensity precision and scale constancy were used. The problem was solved through comparison of intra-sample site-occupancy ratios between Sb-doped and undoped samples. In the second example, high quality, high resolution neutron powder diffraction data were required. The problem was to distinguish between two subtly different models of kaolinite for which the R-weighted-pattern values differed only by 2 or 3 units in the third digit and, particularly, to understand the basis for the consistent programmatic choice of one of the models (PI) over the other. The answer was found in the calculated and 'observed' intensities for (h+ k)-odd reflections; although they were very small, less than 1% of the intensities of the main reflections, many of them were distinctly nonzero. Even though these reflections were not separately observable, because of overlap and small size, they nonetheless correlated with one model sufficiently better than the other to produce the consistent choice.

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.

Structure Refinement of High-Density Polyethylene Using X-Ray Powder Diffraction Data and the Rietveld Method

1995 ◽  
Vol 39 ◽  
pp. 515-521
Author(s):  
Kenneth B. Schwartz ◽  
Robert B. Von Dreele
Keyword(s):  
Powder Diffraction ◽  
Diffraction Data ◽  
High Density Polyethylene ◽  
Rietveld Method ◽  
Structure Refinement ◽  
High Density ◽  
Powder Diffraction Data ◽  
X Ray ◽  
Voigt Profile ◽  
Full Structure

A full structure analysis of a completely crystallized sample of high-density polyethylene (HDPE) has been achieved using x-ray powder diffraction data collected on a laboratory-based powder diffractometer. The structure refinement is performed using the Rietveld method and includes refinement of the carbon and hydrogen atomic positions and temperature factors. The C-C and C-H bond distances and the C-C-C bond angle along the polyethylene chain have been calculated from the refined atomic positions and are in very good agreement with previous experimental and modelling determinations. Evaluations of the pseudo-Voigt profile parameters for Lorentzian strain broadening and me Scherrer coefficient for Gaussian broadening yield reasonable values for microstrain and particle size for this sample. Refinement of the preferred orientation parameter indicates that the HDPE flakes consist of platy crystals or lamellae that are packed normal to the diffraction vector.

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