Use of X-Ray Powder Diffraction Rietveld Pattern-Fitting for Characterising Preferred Orientation in Gibbsites

1990 ◽  
Vol 5 (2) ◽  
pp. 79-85 ◽  
Author(s):  
Li Deyu ◽  
Brian H. O'Connor ◽  
Gerald I.D. Roach ◽  
John B. Cornell
Keyword(s):  
Powder Diffraction ◽  
Correction Method ◽  
Preferred Orientation ◽  
Empirical Measure ◽  
General Application ◽  
X Ray ◽  
Line Intensities ◽  
Orientation Effects ◽  
Xrpd Pattern

AbstractA study has been conducted with gibbsite specimens, on the use of Rietveld X-ray powder diffraction (XRPD) pattern fitting for quantitating preferred orientation in powders. This study has shown that an earlier formula gives results which correlate closely with an empirical measure of morphology proposed recently for gibbsite powders, viz., the ratio of the XRPD intensities for the (002) line and the (110, 200) doublet lines. A method is proposed on the basis of this correlation for the correction for preferred orientation of line intensities in gibbsite powder patterns. The correction method appears to have excellent potential for XRPD quantification of gibbsite levels in mixtures, and could have general application for coping with preferred orientation effects in the quantitation of other phases.

Use of an air brush to spray dry samples for X-ray powder diffraction

Clay Minerals ◽  
1999 ◽  
Vol 34 (1) ◽  
pp. 127-135 ◽  
Author(s):  
S. Hillier
Keyword(s):  
Bulk Density ◽  
Powder Diffraction ◽  
Marked Improvement ◽  
Smooth Surface ◽  
Preferred Orientation ◽  
Spray Drier ◽  
Spray Dry ◽  
X Ray ◽  
Spray Gun ◽  
Spray Dried

AbstractThe construction and operation of a spray drier is described where the spray is produced using an air brush, essentially a miniature spray gun. The spray-dried products consist of spheres 50–60 µm in diameter and typical product recoveries are 80%, a marked improvement over simple two-nozzle systems. The spray-dried samples are easy to load into XRD powder holders and present a smooth surface and relatively constant bulk density to the X-ray beam. Problems of preferred orientation are effectively eliminated and the resulting X-ray powder patterns are completely reproducible by different operators.

X-ray Powder Diffraction QPA by Rietveid Pattern- Fitting - Scope and Limitations

1989 ◽  
Vol 33 ◽  
pp. 269-275 ◽  
Author(s):  
B.H. O'Cannar ◽  
Li Deyu ◽  
B. Jordan ◽  
M. D. Raven ◽  
P. G. Fazey
Keyword(s):  
Powder Diffraction ◽  
Preferred Orientation ◽  
Analytical Science ◽  
Materials Analysis ◽  
X Ray ◽  
University Of Technology ◽  
Science Group

AbstractThe X-ray Analytical Science Group at Curtin university of Technology has been developing and evaluating Rietveld pattern-fitting for materials analysis since 1985. The results are reviewed with particular reference to preferred orientation, crystallinity and phase abundance.

Comparative evaluation of the March and generalized spherical harmonic preferred orientation models using X-ray diffraction data for molybdite and calcite powders

2005 ◽  
Vol 38 (1) ◽  
pp. 158-167 ◽  
Author(s):  
Husin Sitepu ◽  
Brian H. O'Connor ◽  
Deyu Li
Keyword(s):  
Powder Diffraction ◽  
Diffraction Data ◽  
Spherical Harmonic ◽  
Comparative Evaluation ◽  
Preferred Orientation ◽  
Composition Analysis ◽  
Powder Diffraction Data ◽  
X Ray Diffraction ◽  
Crystalline Materials ◽  
X Ray

Preferred crystallographic orientation,i.e.texture in crystalline materials powder diffraction data, can cause serious systematic errors in phase composition analysis and also in crystal structure determination. The March model [Dollase (1986).J. Appl. Cryst.19, 267–272] has been used widely in Rietveld refinement for correcting powder diffraction intensities with respect to the effects of preferred orientation. In the present study, a comparative evaluation of the March model and the generalized spherical harmonic [Von Dreele (1997).J. Appl. Cryst.30, 517–525] description for preferred orientation was performed with X-ray powder diffraction data for molybdite (MoO3) and calcite (CaCO3) powders uniaxially pressed at five different pressures. Additional molybdite and calcite powders, to which 50% by weight silica gel had been added, were prepared to extend the range of preferred orientations considered. The patterns were analyzed initially assuming random orientation of the crystallites and subsequently the March model was used to correct the preferred orientation. The refinement results were compared with parallel refinements conducted with the generalized spherical harmonic [Sitepu (2002).J. Appl. Cryst.35,274–277]. The results obtained show that the generalized spherical harmonic description generally provided superior figures-of-merit compared with the March model results.

X-ray powder diffraction data for acetamidinium formate C3H8N2O2, elimination of preferred orientation effect

2017 ◽  
Vol 32 (4) ◽  
pp. 268-270
Author(s):  
J. Maixner ◽  
P. Kačer
Keyword(s):  
Powder Diffraction ◽  
Diffraction Data ◽  
Unit Cell Volume ◽  
Preferred Orientation ◽  
Unit Cell ◽  
Powder Diffraction Data ◽  
Unit Cell Parameters ◽  
Space Group ◽  
X Ray ◽  
Cell Parameters

X-ray powder diffraction data, unit-cell parameters, and space group for acetamidinium formate, C3H8N2O2, are reported [a = 6.4564(5) Å, c = 13.021 (3) Å, unit-cell volume V = 542.8(3) Å3, M.p. = 215(1)°C, ρc = 1.274 g.cm−3, ρm = 1.269 g.cm−3, Z = 4, and space group P43212]. The front-loaded technique got sample with strong preferred orientation because of plate-like shape of crystallites, so the capillary packing was used for final powder data collection. All measured lines were indexed and are consistent with the P43212 space group. No detectable impurities were observed.

scholarly journals Defocusing Correction of X-Ray Pole Figures by Means of Neutron Pole Figure Measurement

2000 ◽  
Vol 34 (1) ◽  
pp. 55-62 ◽  
Author(s):  
H. Siemes ◽  
C. A. Rosière ◽  
P. Hackspacher ◽  
W. Schäfer ◽  
E. Jansen
Keyword(s):  
Pole Figure ◽  
Correction Method ◽  
Preferred Orientation ◽  
Neutron Measurement ◽  
X Ray ◽  
Pole Figures ◽  
Pole Figure Data

A rather simple empirical defocusing correction method is described which makes use of X-ray and neutron measurement of pole figure data from a sample with a weak preferred orientation.

Quantitative analysis of mannitol polymorphs. X-ray powder diffractometry—exploring preferred orientation effects

2002 ◽  
Vol 28 (6) ◽  
pp. 1149-1159 ◽  
Author(s):  
Sarra N Campbell Roberts ◽  
Adrian C Williams ◽  
Ian M Grimsey ◽  
Steven W Booth
Keyword(s):  
Quantitative Analysis ◽  
Preferred Orientation ◽  
X Ray ◽  
Orientation Effects

Texture Characterisation in X-Ray Powder Diffraction using the March Formula

1991 ◽  
Vol 35 (A) ◽  
pp. 277-283 ◽  
Author(s):  
B.H. O'Connor ◽  
D.Y. Li ◽  
H. Sitepu
Keyword(s):  
Powder Diffraction ◽  
Systematic Errors ◽  
Rietveld Analysis ◽  
Preferred Orientation ◽  
Ratio Method ◽  
Powder Diffraction Data ◽  
Selected Lines ◽  
General Applicability ◽  
Crystalline Materials ◽  
X Ray

AbstractTexture, i.e. preferred orientation (PO), of crystallites can cause serious systematic errors in quantitative analysis of crystalline materials using x-ray powder diffraction (XRPD) data. The singleparameter model of March (1932), proposed by Dollase (1986) for use in powder diffractometry is a promising mathematical formalism for correcting PO in XRPD analysis of uniaxially-oriented specimens. O'Connor et al. (1991) successfully applied the March formula in applying preferred orientation corrections for gibbsites, Al(OH)3, using Rietveld pattern-fitting and a line ratio method in which corrections are determined according to the intensity ratios of selected lines. The paper gives an appraisal of the general applicability of the methods considered by Li and O'Connor with particular reference to powder diffraction data for gibbsite, molybdite (MoO3), calcite (CaCO3) and kaolinite specimens. It is shown that some caution should be exercised when using the March formula to describe PO in Rietveld analysis.

Parallel-beam X-ray diffractometry using X-ray guide tubes

2000 ◽  
Vol 33 (2) ◽  
pp. 389-391 ◽  
Author(s):  
Toyoko Yamanoi ◽  
Hiromoto Nakazawa
Keyword(s):  
Large Diameter ◽  
Preferred Orientation ◽  
X Rays ◽  
X Ray Diffraction ◽  
Parallel Beam ◽  
X Ray ◽  
Orientation Effects ◽  
Powder Samples ◽  
Xrd Patterns ◽  
Integrated Intensities

A parallel-beam X-ray diffraction geometry using X-ray guide tubes is proposed to eliminate preferred-orientation effects in powder X-ray diffraction (XRD) patterns and for new applications of XRD. A bundle of X-ray guide tubes (polycapillaries) is used to provide an intense quasi-parallel (approximately 0.2° divergence) and large-diameter (approximately 20 mm) beam of X-rays needed for parallel-beam diffractometry. Mica and silicon particles were agitated inside a cylindrical chamber by a steady flow of N2gas so that they were randomly oriented. The quasi-parallel incident X-ray beam passed through the cloud of floating particles. The diffracted X-rays were detected using a standard 2θ diffractometer. The integrated intensities observed agree well with those calculated from the known model of the crystal structure. This result demonstrates that this type of diffractometry is capable of avoiding preferred-orientation effects and of collecting XRD data for moving powder samples.

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