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.

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.

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.

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.

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.

Obtaining optimal structural data from X-ray powder diffraction using the Rietveld method

2014 ◽  
Vol 29 (4) ◽  
pp. 396-403 ◽  
Author(s):  
Shanke Liu ◽  
He Li ◽  
Jianming Liu
Keyword(s):  
Crystal Structure ◽  
Powder Diffraction ◽  
Diffraction Data ◽  
Rietveld Method ◽  
Low Cost ◽  
Structural Data ◽  
Preferred Orientation ◽  
X Ray

Diffraction data of calcite were collected using a conventional Bragg–Brentano diffractometer, which is a convenient, low-cost, and highly popular in-house instrument, and its crystal structure was refined by the Rietveld method. This paper shows how one treats preferred orientation and how different refinement strategies affect the accuracy of the result.

The Effects of Extinction on X-Ray Powder Diffraction Intensities

1986 ◽  
Vol 30 ◽  
pp. 447-456 ◽  
Author(s):  
Janies P. Cline ◽  
Robert L. Snyder
Keyword(s):  
Spray Drying ◽  
Powder Diffraction ◽  
Preferred Orientation ◽  
Drying Process ◽  
Statistical Nature ◽  
X Ray ◽  
Intensity Measurements

Several factors have long been known to affect the intensity measurements of X-ray powder diffraction. The characterization of these effects has been impeded by difficulties in their isolation and the statistical nature of the data in which they manifest themselves. The most celebrated, and most detrimental, of the these effects is that of preferred orientation. This error can be eliminated with the spherical agglomeration of the sample (1). The spray drying process offers this result and is considered to have the broadest range of applicability to materials encountered by the powder diffractionist.

X-ray powder diffraction study of synthetic Palmierite, K2Pb(SO4)2

2001 ◽  
Vol 16 (2) ◽  
pp. 92-97 ◽  
Author(s):  
Ralph G. Tissot ◽  
Mark A. Rodriguez ◽  
Diana L. Sipola ◽  
James A. Voigt
Keyword(s):  
Powder Diffraction ◽  
Synthesis Method ◽  
Intensity Variation ◽  
Rietveld Analysis ◽  
Annealed Sample ◽  
Preferred Orientation ◽  
Chemical Inhomogeneity ◽  
Crystal Data ◽  
X Ray ◽  
Cell Parameters

Palmierite (K2Pb(SO4)2) has been prepared via a chemical synthesis method. Intensity differences were observed when X-ray powder data from the newly synthesized compound were compared to the published powder diffraction card (PDF) 29-1015 for Palmierite. Investigation of these differences indicated the possibility of preferred orientation and/or chemical inhomogeneity affecting intensities, particularly those of the basal (00l) reflections. Annealing of the Palmierite was found to reduce the effects of preferred orientation. Electron microprobe analysis confirmed K:Pb:S as 2:1:2 for the for the annealed Palmierite powder. Subsequent least-squares refinement and Rietveld analysis of the annealed powder showed peak intensities very close to that of a calculated Palmierite pattern (based on single crystal data), yet substantially higher than many of the PDF 29-1015 published intensities. Further investigation of peak intensity variation via calculated patterns suggested that the intensity discrepancies between the annealed sample and those found in PDF 29-1015 were potentially due to chemical variation in the K2Pb(SO4)2 composition. X-ray powder diffraction and crystal data for Palmierite are reported for the annealed sample. Palmierite is trigonal/hexagonal with unit cell parameters a=5.497(1) Å, c=20.864(2) Å, space group R-3m(166), and Z=3.

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