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.

scholarly journals Study of selection and purification of Brazilian bentonite clay by elutriation: a XRF, SEM and Rietveld analysis

Cerâmica ◽  
2016 ◽  
Vol 62 (361) ◽  
pp. 1-8 ◽  
Author(s):  
J. L. Alves ◽  
A. E. Zanini ◽  
M. E. de Souza ◽  
M. L. F. Nascimento
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Rietveld Method ◽  
Bentonite Clay ◽  
Rietveld Analysis ◽  
Industrial Applications ◽  
X Ray Diffraction ◽  
X Ray ◽  
Almost All ◽  
Scanning Electron

Abstract Clays obtained from nature have a lot of impurities. Therefore, for best using of these materials, it is necessary its selection and purification. Thus, the aim of this work is to separate and to purify the smectite fractions using water as a solvent at a low flux mixed with a bentonite clay extracted from a mine in Vitória da Conquista - Bahia / Brazil. For this a separation method of fractions of expandable clays based on the Stokes' Law was applied - this process is called elutriation, in order to ensure and to expand possible industrial applications of this material. The samples were characterized by analysis of X-ray diffraction, X-ray fluorescence and scanning electron microscopy. The Rietveld method enabled the quantification of main phase minerals: montmorillonite, kaolinite, nontronite and quartz, reaching 85% in mass of montmorillonite phase at the end of the process. Results showed that the method used was efficient to remove almost all quartz, carbonates and organic matter from the sample. It was also observed a monomodal grain size distribution of elutriated materials with thinner grains, around (18.1 ± 1.8) μm at the end of the process. It has been concluded that the method developed and applied showed promising characters to be applied to elutriate kilograms of clays and could be used in industrial scale.

Structure of Carbonated Hydroxyapatite Based on Rietveld Method

2008 ◽  
Vol 368-372 ◽  
pp. 1187-1189
Author(s):  
Xu Ran ◽  
Jun Guo Ran ◽  
Li Gou ◽  
Ji Yong Chen ◽  
Jiao Min Luo
Keyword(s):  
Crystal Structure ◽  
Sintering Temperature ◽  
Rietveld Method ◽  
Rietveld Analysis ◽  
Structure Parameters ◽  
X Ray Diffraction ◽  
Carbonated Hydroxyapatite ◽  
X Ray ◽  
Quantitative Results ◽  
Distortion Index

The crystalline structures of B-type carbonated hydroxyapatite (CHA) powders sintered at 700, 900 and 1100°C, respectively, were studied by Rietveld analysis of powder X-ray diffraction (XRD) data. A series of structure parameters, including lattice parameters (a and c), bond length and the distortion index of PO4 tetrahedron (Dind) were calculated by Rietveld method to characterize the fine structure of CHA. The broadening effect of XRD reflections was separated to calculate the micro-strain and crystalline size. The results showed that CHA become more stable with the increase of sintering temperature, but the CO3 2- is almost lost at temperature of 1100°C. The quantitative results about crystal structure of CHA based on crystalline structure simulated by Rietveld method are obtained.

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.

A semi-empirical asymmetry function for X-ray diffraction peak profiles

1995 ◽  
Vol 10 (3) ◽  
pp. 204-206 ◽  
Author(s):  
P. Riello ◽  
P. Canton ◽  
G. Fagherazzi
Keyword(s):  
Goodness Of Fit ◽  
Rietveld Method ◽  
Rietveld Analysis ◽  
Opening Angle ◽  
X Ray Diffraction ◽  
X Ray ◽  
Asymmetry Function ◽  
The Asymmetry ◽  
Fit Index ◽  
Semi Empirical

A new semi-empirical approximation for the asymmetry function to be used in the X-ray Rietveld analysis has resulted in lower values of the so-called goodness-of-fit index, defined as S = Rwp/Rexp, where Rwp is the R-weighted pattern and Rexp is the R-expected [R. A. Young, The Rietveld Method (Oxford U.P., Oxford, 1993)], with respect to the corresponding values obtained with the classical approximation used by Rietveld in his fundamental paper. A comparing test of the two asymmetry functions was carried out for the cubic Y2O3 and for αAl2O3 using either pseudo-Voigt or Pearson VII symmetrical functions and two diffractometers. As in the case of the Rietveld approximation, the present one, which employs an exponential function, is optimized using only one fitting parameter. Experimentally, the asymmetry can be considerably diminished by using Soller slits with a small opening angle (≤2°).

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.

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).

scholarly journals Rietveld Analysis on X-Ray Diffraction Of South Kalimantan Kaolin Clays

2018 ◽  
Vol 6 (2) ◽  
pp. 171
Author(s):  
Ruliana Febrianti ◽  
Firda Herlina ◽  
Muhammad Saukani
Keyword(s):  
Quantitative Analysis ◽  
Goodness Of Fit ◽  
Least Squares Method ◽  
Rietveld Method ◽  
Rietveld Analysis ◽  
Peak Height ◽  
Peak Position ◽  
X Ray Diffraction ◽  
X Ray ◽  
The Difference

At least 13 million tons of kaolin claystone lie in several regencies of South Kalimantan covering Banjar, Tapin, Hulu Sungai Utara and Kotabaru regencies. This paper reports an attempt to explore their crystalline state characteristics, projecting their potential use for geopolymer. Sungai Tabuk, Cintapuri and Tatakan, due to their largest kaolin claystone deposits, were chosen as the sampling sites. The kaolin samples were prepared by syphoning method prior to X-ray diffraction (XRD) characterizations in determining their crystalline phases. X’Pert HighScore Plus and Rietica software were respectively responsible for the qualitative and quantitative phase analyses. The qualitative analysis used search and match method at peak position and peak height between measured and calculated diffraction patterns. Our study revealed the existence of two main phases in the sample, i.e. quartz (SiO2) and kaolinite (Al2Si2O5(OH)4). In addition, the Quantitative analysis used the Rietveld method with the least squares method approach. Rietveld refinement was based on a goodness of fit score of less than 4% by minimizing the difference in the character of the diffraction pattern (position, height, width and peak shape) between the observed and the calculated XRD patterns. The Rietveld quantitative analysis shows, Tatakan is an area with kaolinite-richest deposit (±84%), followed by Cintapuri (±76%) and Tabuk (±70%); quartz is found in reverse.

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