Rietveld refinement of the gadolinium strontium oxide SrGd2O4

2003 ◽  
Vol 18 (4) ◽  
pp. 288-292 ◽  
Author(s):  
H. Chaker ◽  
A. Kabadou ◽  
M. Toumi ◽  
R. Ben Hassen
Keyword(s):  
Rietveld Refinement ◽  
Rietveld Method ◽  
Lattice Parameters ◽  
Related Structure ◽  
Orthorhombic Symmetry ◽  
Strontium Oxide ◽  
X Ray Diffraction ◽  
X Ray ◽  
New Phase

Powder X-ray diffraction (XRD) data were collected for a new phase of SrGd2O4. Analysis using the Rietveld method was carried out and it was found that the sample crystallizes in the orthorhombic symmetry with CaFe2O4 related structure. The lattice parameters are found to be a=12.0521(2) Å, b=10.1327(2) Å, c=3.4757(4) Å and Z=4. For X-ray data RF=4.9%, RB=7.6%, RP=8.1% and χ2=1.51. The structure can be described as an assembly of bioctahedron [Gd2O10] which are linked together by O2− anions and of dodecahedron of SrO8.

Rietveld refinement X-ray powder data of Pr0.7Ba0.3MnO3

2003 ◽  
Vol 18 (1) ◽  
pp. 29-31
Author(s):  
M. Ellouze ◽  
W. Boujelben ◽  
H. Fuess
Keyword(s):  
Solid State ◽  
Rietveld Refinement ◽  
Solid State Reaction ◽  
Rietveld Method ◽  
Xrd Analysis ◽  
Orthorhombic Symmetry ◽  
X Ray Diffraction ◽  
Conventional Solid State Reaction ◽  
Space Group ◽  
X Ray

Powder X-ray diffraction (XRD) data were collected for Pr0.7Ba0.3MnO3. This sample was prepared using the conventional solid state reaction by mixing Pr6O11, Mn2O3, and BaCO3 up to 99.9% purity at 1400 °C in air for 60 h. XRD analysis using the Rietveld method was carried out and it was found that this manganite sample has orthorhombic symmetry with Pnma space group. The lattice parameters are found to be a=5.4900 Å, b=7.7578 Å, and c=5.5227 Å.

scholarly journals Dielectric and Raman studies of Ba0.06(Na1/2Bi1/2)0.94TiO3–NaNbO3 ceramics

2016 ◽  
Vol 34 (2) ◽  
pp. 437-445 ◽  
Author(s):  
Sumit K. Roy ◽  
S. Chaudhuri ◽  
R.K. Kotnala ◽  
D.K. Singh ◽  
B.P. Singh ◽  
...  
Keyword(s):  
Single Phase ◽  
Solid State Reaction Method ◽  
Lead Free ◽  
Orthorhombic Symmetry ◽  
Dielectric Studies ◽  
X Ray Diffraction ◽  
Reaction Method ◽  
X Ray ◽  
New Phase ◽  
Diffusivity Parameter

AbstractIn this work the X-ray diffraction, scanning electron microscopy, Raman and dielectric studies of lead free perovskite (1 – x)Ba0.06(Na1/2Bi1/2)0.94TiO3–xNaNbO3 (0 ⩽ x ⩽ 1.0) ceramics, prepared using a standard solid state reaction method, were investigated. X-ray diffraction studies of all the ceramics suggested the formation of single phase with crystal structure transforming from rhombohedral-tetragonal to orthorhombic symmetry with the increase in NaNbO3 content. Raman spectra also confirmed the formation of solid solution without any new phase. Dielectric studies showed that the phase transition is of diffusive character and diffusivity parameter decreases with increasing NaNbO3 content. The compositional fluctuation was considered to be the main cause of diffusivity.

Crystal structure and powder X-ray diffraction data for new Tb3CuAl3Ge2 compound

2015 ◽  
Vol 30 (1) ◽  
pp. 63-66 ◽  
Author(s):  
Chao Zeng ◽  
Guoqiang Lin ◽  
Weijing Zeng ◽  
Wei He
Keyword(s):  
Crystal Structure ◽  
Rietveld Refinement ◽  
Diffraction Data ◽  
Rietveld Method ◽  
Unit Cell ◽  
Type Structure ◽  
X Ray Diffraction ◽  
Quaternary Compound ◽  
Space Group ◽  
X Ray

The crystal structure of new Tb3CuAl3Ge2 quaternary compound was studied by the Rietveld method from powder X-ray diffraction (XRD) data. The Tb3CuAl3Ge2 compound crystallized in the hexagonal Y3NiAl3Ge2-type structure with space group P-62m (no. 189) and lattice parameters a = 7.0041(2) Å, c = 4.1775(1) Å, V = 177.48 Å3. There is only one formula in each unit cell, Z = 1, and the density of Tb3CuAl3Ge2 is ρx = 7.1696 g cm−3. The reliability factors characterizing the Rietveld refinement results are Rp = 6.43%, Rwp = 8.65%, RB = 4.81%, and RF = 4.09%, respectively. The powder XRD data of Tb3CuAl3Ge2 were presented and the reliability of indexation is F30 = 120.9(0.0073, 34).

scholarly journals Psilocybin: crystal structure solutions enable phase analysis of prior art and recently patented examples

2022 ◽  
Vol 78 (1) ◽  
Author(s):  
Alexander M. Sherwood ◽  
Robert B. Kargbo ◽  
Kristi W. Kaylo ◽  
Nicholas V. Cozzi ◽  
Poncho Meisenheimer ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Rietveld Refinement ◽  
Phase Analysis ◽  
Density Functional ◽  
Rietveld Method ◽  
Quantitative Phase Analysis ◽  
Published Data ◽  
Dihydrogen Phosphate ◽  
X Ray Diffraction ◽  
X Ray

Psilocybin {systematic name: 3-[2-(dimethylamino)ethyl]-1H-indol-4-yl dihydrogen phosphate} is a zwitterionic tryptamine natural product found in numerous species of fungi known for their psychoactive properties. Following its structural elucidation and chemical synthesis in 1959, purified synthetic psilocybin has been evaluated in clinical trials and has shown promise in the treatment of various mental health disorders. In a recent process-scale crystallization investigation, three crystalline forms of psilocybin were repeatedly observed: Hydrate A, Polymorph A, and Polymorph B. The crystal structure for Hydrate A was solved previously by single-crystal X-ray diffraction. This article presents new crystal structure solutions for the two anhydrates, Polymorphs A and B, based on Rietveld refinement using laboratory and synchrotron X-ray diffraction data, and density functional theory (DFT) calculations. Utilizing the three solved structures, an investigation was conducted via Rietveld method (RM) based quantitative phase analysis (QPA) to estimate the contribution of the three different forms in powder X-ray diffraction (PXRD) patterns provided by different sources of bulk psilocybin produced between 1963 and 2021. Over the last 57 years, each of these samples quantitatively reflect one or more of the hydrate and anhydrate polymorphs. In addition to quantitatively evaluating the composition of each sample, this article evaluates correlations between the crystal forms present, corresponding process methods, sample age, and storage conditions. Furthermore, revision is recommended on characterizations in recently granted patents that include descriptions of crystalline psilocybin inappropriately reported as a single-phase `isostructural variant.' Rietveld refinement demonstrated that the claimed material was composed of approximately 81% Polymorph A and 19% Polymorph B, both of which have been identified in historical samples. In this article, we show conclusively that all published data can be explained in terms of three well-defined forms of psilocybin and that no additional forms are needed to explain the diffraction patterns.

Phase Relation of FeS2-VS2 System and New Phase of Defect Troilite Structure

2011 ◽  
Vol 170 ◽  
pp. 92-96 ◽  
Author(s):  
Yoshihisa Miyata ◽  
Koya Hayashi ◽  
Genta Sakane ◽  
Takaaki Arimoto ◽  
Yasuhiro Katayama ◽  
...  
Keyword(s):  
Magnetic Property ◽  
Transition Temperature ◽  
Rietveld Method ◽  
Diffraction Method ◽  
Silica Tube ◽  
X Ray Diffraction ◽  
Large Defect ◽  
X Ray ◽  
Property Measurement ◽  
New Phase

A large defective troilite (Fe0.9V0.1)0.82S is prepared by a sealed silica-tube method at 800oC and characterized by a powder X-ray diffraction method and using a magnetic property measurement system. The crystal structures of a defective troilite and non defective troilite are analyzed by Rietveld method. The large defect enhances the Fe-Fe pairing and suppresses the waving of Fe-chain along c-direction. The antiferromagnetic property is observed on both troilites. The spin-flip transition temperature of the large defective troilite is 9K.

scholarly journals Reinvestigation of the crystal structure of Ca2Ce8(SiO4)6O2 apatite by Rietveld refinement

2018 ◽  
Vol 74 (7) ◽  
pp. 955-959 ◽  
Author(s):  
Nicolas Massoni ◽  
Ronan Hegron ◽  
Lionel Campayo
Keyword(s):  
Crystal Structure ◽  
Cell Volume ◽  
Rietveld Refinement ◽  
Diffraction Data ◽  
Rietveld Method ◽  
X Ray Diffraction ◽  
Space Group ◽  
X Ray ◽  
Apatite Type

Ca2 Ln 8(SiO4)6O2 apatites with Ln = La, Ce, Pr, Nd, Sm, Eu, Gd and Tb crystallize in space group P63/m. The crystal structure of apatite-type Ca2Ce8(SiO4)6O2 [dicalcium octacerium hexakis(silicate) dioxide], which has been synthesized by calcination, was refined from powder X-ray diffraction data using the Rietveld method. A database survey shows that contrary to the previously published Ca2Ce8(SiO4)6O2 structure [Skakle et al. (2000). Powder Diffr. 15, 234–238], the cell volume of the structure reported here is consistent with those of other Ln apatites.

Rietveld refinement of LaB6: data from µXRD

2005 ◽  
Vol 38 (5) ◽  
pp. 757-759 ◽  
Author(s):  
Guangrong Ning ◽  
Roberta L. Flemming
Keyword(s):  
Rietveld Refinement ◽  
Diffraction Data ◽  
Structural Information ◽  
Rietveld Method ◽  
Structure Refinement ◽  
Quality Data ◽  
X Ray Diffraction ◽  
Diffraction Profile ◽  
Standard Material ◽  
X Ray

The Rietveld method of crystal structure refinement was an important breakthrough, allowing crystal structural information to be obtained from powder diffraction data. One remaining challenge is to collect Rietveld-quality data for polycrystalline mineralsin situ, using laboratory-based micro X-ray diffraction (µXRD) techniques. Here a new data collection method is presented, called `multiframes', which produces high-quality data, suitable for Rietveld refinement, using the Bruker D8 DISCOVER micro X-ray diffractometer. 91 frames of two-dimensional X-ray diffraction data were collected for powdered NIST SRM 660 LaB6standard material, using a general area-detector diffraction system (GADDS), at intervals of 0.8° 2θ. For each frame, only the central 1° 2θ was integrated and merged to produce a diffraction profile from 17 to 90° 2θ. Rietveld refinement of this data usingTOPAS2gave a unit-cell parameter (ao) and atomic position of boron (x) for LaB6of 4.1549 (1) Å and 0.1991 (9), respectively (Rwp= 4.26,RBragg= 3.21). The corresponding La—B bond length was calculated to be 3.0522 Å. These parameters are in good agreement with the literature values for LaB6. These encouraging results suggest that Rietveld-quality micro X-ray diffraction data can be collected from the Bruker D8 DISCOVER diffractometer, provided that the GADDS detector is stepped in small increments, for each frame only the central 1° 2θ is integrated at constant arc length, and counting time is sufficient to yield adequate intensity (∼10 000 counts).

scholarly journals Crystal structure and powder X-ray diffraction data of the super-paramagnetic compound CuFeInTe3

2021 ◽  
Vol 67 (2 Mar-Apr) ◽  
pp. 305
Author(s):  
G. E. Delgado ◽  
P. Grima-Gallardo ◽  
J. A. Aitken ◽  
H. Cabrera ◽  
J. Cisterna ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Rietveld Refinement ◽  
Diffraction Data ◽  
Rietveld Method ◽  
X Ray Diffraction ◽  
Unit Cell Parameters ◽  
Quaternary Compound ◽  
X Ray ◽  
Cell Parameters ◽  
Figures Of Merit

The crystal structure of the new CuFeInTe3 quaternary compound was studied by the Rietveld method from powder X-ray diffraction data. The CuFeInTe3 compound crystallize in the tetragonal CuFeInSe3-type structure with space group P2c (Nº 112), and unit cell parameters a = 6.1842(1) Å, c = 12.4163(2) Å, V = 474.85(1) Å3. The density of CuFeInTe3 is rx = 5.753 g cm−3. The reliability factors of the Rietveld refinement results are Rp= 5.5%, Rwp= 6.1%, Rexp= 4.7%, and S= 1.3. The powder XRD data of CuFeInTe3 are presented and the figures of merit of indexation are M20 = 79.4 and F30 = 43.3 (0.0045, 154).

Development of a quantification method for quartz in various bulk materials by X-ray diffraction and the Rietveld method

2012 ◽  
Vol 27 (1) ◽  
pp. 12-19 ◽  
Author(s):  
Joannie Martin ◽  
Martin Beauparlant ◽  
Jacques Lesage ◽  
Huu Van Tra
Keyword(s):  
Rietveld Refinement ◽  
Rietveld Method ◽  
General Procedure ◽  
Health And Safety ◽  
Rietveld Analysis ◽  
Crystalline Silica ◽  
International Agency ◽  
X Ray Diffraction ◽  
X Ray ◽  
Almost All

Crystalline silica is known for its health hazards, and since 1997 has been listed as Group 1, Carcinogenic to Humans, by the International Agency for Research on Cancer. This issue is particularly important in the industrial environment, and there is still no method that allows quantification of the different polymorphs of crystalline silica. Many analytical methods have been proposed, and the major problem in almost all cases is attributable to the very large variety of matrixes encountered. This study evaluates the potential of X-ray diffraction techniques and an automated Rietveld analysis in order to overcome this problem and to adapt the quantitative analysis of quartz, the most prevalent crystalline silica polymorph, to routine analysis in the health and safety environment. Matrix simulations are done and many parameters are optimized. Sample preparation, the acquisition program, pattern treatment, and Rietveld refinement are evaluated, and a general procedure is determined. Automation of Rietveld refinement leads to a significant reduction in analysis time, but cannot be applied to every type of sample.

Structure of LaNi3.8AlMn0.2 Compounds Studied by Neutron Powder Diffraction

2016 ◽  
Vol 847 ◽  
pp. 26-28
Author(s):  
Wen Ze Han ◽  
Hao Guo ◽  
Kai Sun ◽  
De Min Chen ◽  
Shi Liu ◽  
...  
Keyword(s):  
Powder Diffraction ◽  
Diffraction Data ◽  
Annealing Temperature ◽  
Rietveld Method ◽  
Neutron Powder Diffraction ◽  
Lattice Parameters ◽  
Linear Variation ◽  
X Ray Diffraction ◽  
X Ray ◽  
Space Groups

The structures of as-cast LaNi3.8AlMn0.2 alloys and subsequent compounds by means of annealing at different temperature (850, 900, 950, 1000 oC) were examined by using neutron powder diffraction (NPD) and X-ray diffraction (XRD). Based on the Rietveld method, the diffraction data was refined using FullProf software. The refined results demonstrate the structure types of all compounds are CaCu5 type and their space groups are P6/mmm. Increasing the annealing temperature, the lattice parameters of LaNi3.8AlMn0.2 compounds did not possess clearly linear variation. It is noted that Mn atoms do not occupy the 2c sites but occupy the 3g sites in all compounds.

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