scholarly journals The suppression of fluorescence peaks in energy-dispersive X-ray diffraction

2014 ◽  
Vol 47 (5) ◽  
pp. 1708-1715 ◽  
Author(s):  
G. M. Hansford ◽  
S. M. R. Turner ◽  
D. Staab ◽  
D. Vernon
Keyword(s):  
Excitation Energy ◽  
Preferred Orientation ◽  
Energy Dispersive ◽  
Source Spectrum ◽  
Natural State ◽  
X Ray Diffraction ◽  
Scattering Angle ◽  
X Ray ◽  
Back Reflection ◽  
Diffraction Peaks

A novel method to separate diffraction and fluorescence peaks in energy-dispersive X-ray diffraction (EDXRD) is described. By tuning the excitation energy of an X-ray tube source to just below an elemental absorption edge, the corresponding fluorescence peaks of that element are completely suppressed in the resulting spectrum. SinceBremsstrahlungphotons are present in the source spectrum up to the excitation energy, any diffraction peaks that lie at similar energies to the suppressed fluorescence peaks are uncovered. This technique is an alternative to the more usual method in EDXRD of altering the scattering angle in order to shift the energies of the diffraction peaks. However, in the back-reflection EDXRD technique [Hansford (2011).J. Appl. Cryst.44, 514–525] changing the scattering angle would lose the unique property of insensitivity to sample morphology and is therefore an unattractive option. The use of fluorescence suppression to reveal diffraction peaks is demonstrated experimentally by suppressing the Ca Kfluorescence peaks in the back-reflection EDXRD spectra of several limestones and dolomites. Three substantial benefits are derived: uncovering of diffraction peak(s) that are otherwise obscured by fluorescence; suppression of the Ca Kescape peaks; and an increase in the signal-to-background ratio. The improvement in the quality of the EDXRD spectrum allows the identification of a secondary mineral in the samples, where present. The results for a pressed-powder pellet of the geological standard JDo-1 (dolomite) show the presence of crystallite preferred orientation in this prepared sample. Preferred orientation is absent in several unprepared limestone and dolomite rock specimens, illustrating an advantage of the observation of rocks in their natural state enabled by back-reflection EDXRD.

A full-pattern fitting algorithm for energy-dispersive X-ray diffraction

2003 ◽  
Vol 36 (5) ◽  
pp. 1123-1127 ◽  
Author(s):  
Yu-Hui Dong ◽  
Jing Liu ◽  
Yan-Chun Li ◽  
Xiao-Dong Li
Keyword(s):  
High Pressure ◽  
Energy Dispersive ◽  
X Ray Diffraction ◽  
X Ray ◽  
Cell Parameters ◽  
Fitting Algorithm ◽  
Diffraction Angle ◽  
Data Points ◽  
Diffraction Peaks ◽  
Very High

A full-pattern fitting algorithm for energy-dispersive X-ray diffraction is proposed, especially for high-pressure X-ray diffraction studies. The algorithm takes into account the errors in measuring the energy and the diffraction angle. A lognormal function is introduced to represent the background. All the peaks that are detectable in the diffraction spectra, including fluorescence and diffraction peaks, are considered together. Because all the data points in the spectra are used, the accuracy of the cell parameters obtained by this method is very high. This is very helpful in the analysis of the equation of state and the identification of new phases under high pressure.

scholarly journals A Study of Preferred Orientation by Energy-Dispersive X-Ray Diffraction

1977 ◽  
Vol 2 (4) ◽  
pp. 243-251 ◽  
Author(s):  
E. Laine ◽  
J. Kivilä ◽  
I. Lähteenmäki
Keyword(s):  
Density Distribution ◽  
Diffraction Method ◽  
Polar Axis ◽  
Preferred Orientation ◽  
Energy Dispersive ◽  
X Ray Diffraction ◽  
Powder Specimen ◽  
X Ray ◽  
Aluminium Powder ◽  
Energy Dispersive Diffraction

The influence of preferred orientation on integrated x-ray intensities in powder specimen using energy-dispersive diffraction method is investigated. The theory used is based upon examination of the polar axis density distribution. The measurements were carried out using the Schulz technique added with defocusing correction. Experimental results are given for three aluminium powder specimens.

scholarly journals Phase-targeted X-ray diffraction

2016 ◽  
Vol 49 (5) ◽  
pp. 1561-1571 ◽  
Author(s):  
G. M. Hansford
Keyword(s):  
Rock Specimen ◽  
Low Cost ◽  
Emission Lines ◽  
Quartz Powder ◽  
X Ray Diffraction ◽  
Scattering Angle ◽  
X Ray ◽  
Diffraction Peaks ◽  
First Time ◽  
Xrd Method

A powder X-ray diffraction (XRD) method to enhance the signal of a specific crystalline phase within a mixture is presented for the first time. Specificity to the targeted phase relies on finding coincidences in the ratios of crystal d spacings and the ratios of elemental characteristic X-ray energies. Such coincidences can be exploited so that the two crystal planes diffract through the same scattering angle at two different X-ray energies. An energy-resolving detector placed at the appropriate scattering angle will detect a significantly enhanced signal at these energies if the target mineral or phase is present in the sample. When implemented using high scattering angles, for example 2θ > 150°, the method is tolerant to sample morphology and distance on the scale of ∼2 mm. The principle of the method is demonstrated experimentally using Pd Lα1 and Pd Lβ1 emission lines to enhance the diffraction signal of quartz. Both a pure quartz powder pellet and an unprepared mudstone rock specimen are used to test and develop the phase-targeted method. The technique is further demonstrated in the sensitive detection of retained austenite in steel samples using a combination of In Lβ1 and Ti Kβ emission lines. For both these examples it is also shown how the use of an attenuating foil, with an absorption edge close to and above the higher-energy characteristic X-ray line, can serve to isolate to some degree the coincidence signals from other fluorescence and diffraction peaks in the detected spectrum. The phase-targeted XRD technique is suitable for implementation using low-cost off-the-shelf components in a handheld or in-line instrument format.

scholarly journals Quantitative Determination of Preferred Orientation by Energy-Dispersive X-Ray Diffraction

1976 ◽  
Vol 2 (2) ◽  
pp. 95-111 ◽  
Author(s):  
L. Gerward ◽  
S. Lehn ◽  
G. Christiansen
Keyword(s):  
Quantitative Determination ◽  
Rolling Texture ◽  
Tension Test ◽  
Preferred Orientation ◽  
Energy Dispersive ◽  
X Ray Diffraction ◽  
X Ray ◽  
Fibre Texture

The use of energy-dispersive X-ray diffraction for quantitative determination of preferred orientations in polycrystalline specimens is analysed. The method is applied to determinations of rolling texture and fibre texture. The adaptability of the method to in situ studies is demonstrated by observations of texture changes simultaneous with the deformation of a specimen in a tension test.

Back-reflection energy-dispersive X-ray diffraction: a novel diffraction technique with almost complete insensitivity to sample morphology

2011 ◽  
Vol 44 (3) ◽  
pp. 514-525 ◽  
Author(s):  
Graeme Mark Hansford
Keyword(s):  
Fluorescence Analysis ◽  
Planetary Science ◽  
Energy Dispersive ◽  
X Ray Diffraction ◽  
Intrinsic Geometry ◽  
X Ray ◽  
Back Reflection ◽  
Minimal Sample ◽  
Analysis Application ◽  
Diffraction Patterns

A novel X-ray diffraction (XRD) technique, which exhibits almost complete insensitivity to the morphology of and distance to the sample, is presented for the first time. This technique applies energy-dispersive XRD (EDXRD) in a back-reflection geometry, with 2θ ≃ 180°. Although this geometry leads to low resolution of diffraction peaks and the greatest overlap with fluorescence peaks, it nevertheless yields a combination of properties that are unique in the field of X-ray diffractometry. It is likely that diffraction patterns can be obtained with no or very minimal sample preparation. Furthermore, the intrinsic geometry of the method and the simplicity inherent to EDXRD enables a compact lightweight instrument design, suitable for field-portable or hand-held XRD and X-ray fluorescence analysis. Application to geological and planetary science is emphasized in this paper. The characteristics of the technique are elucidatedviatheoretical considerations and ray-trace modelling, and the simplest possible implementation is described.

Novel Structure of MgSe in the Multimegabar Regime: Positional Parameter Determination

1997 ◽  
Vol 499 ◽  
Author(s):  
Arthur L. Ruoff ◽  
Ting Li ◽  
Chandrabhas Narayana ◽  
Huan Luo ◽  
Raymond G. Greene
Keyword(s):  
Equation Of State ◽  
Structural Transformations ◽  
Energy Dispersive ◽  
Parameter Determination ◽  
X Ray Diffraction ◽  
X Ray ◽  
Positional Parameter ◽  
Novel Structure ◽  
Diffraction Peaks ◽  
Intensity Calculation

ABSTRACTThe structural transformations in the II-VI compound MgSe have been studied under pressure using energy dispersive x-ray diffraction. MgSe transforms ‘continuously’ from the rocksalt (Bl) structure to a FeSi (B28) or Au-Be structure beginning at 99 ± 8 GPa. At 202 GPa, MgSe is approaching 7-fold coordination with u = 0.0828 and w = 0.4173. The method for intensity calculation of the diffraction peaks is presented. Using the Birch equation, the equation of state to 146 GPa was determined with Bo = 62.8 + 1.6 GPa and Bo′ = 4.1.

scholarly journals Correction of Integrated X-Ray Intensities for Preferred Orientation in Hexagonal Close-Packed Powders Using Edxrd

1980 ◽  
Vol 4 (2) ◽  
pp. 63-71 ◽  
Author(s):  
J. Kivilä ◽  
E. Laine ◽  
S. Parviainen
Keyword(s):  
Density Distribution ◽  
Polar Axis ◽  
Preferred Orientation ◽  
Energy Dispersive ◽  
X Ray Diffraction ◽  
X Ray ◽  
Hexagonal Close Packed ◽  
Integrated Intensities

It is shown that energy-dispersive x-ray diffraction (EDXRD) method can be used for correction of integrated intensities for preferred orientation in hexagonal close-packed powders. The theory is based upon examination of the polar axis density distribution and upon the use of hexagonal harmonics in its representation. The reflexion method by Schulz added with defocusing correction was used. Measurements were carried out on three zinc samples with different degrees of orientation, the largest correction being 54 percent.

scholarly journals Identification of preferentially exposed crystal facets by X-ray diffraction

RSC Advances ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 5585-5589 ◽  
Author(s):  
Liping Zhang ◽  
Alexandre A. S. Gonçalves ◽  
Mietek Jaroniec
Keyword(s):  
Preferred Orientation ◽  
X Ray Diffraction ◽  
X Ray ◽  
Diffraction Peaks ◽  
Exposed Facets ◽  
Anisotropic Nanostructures

Intensification of X-ray diffraction peaks can be used to get information about doping, presence of vacancies, anisotropic nanostructures, or preferred orientation of crystals with largely exposed facets.

Fast quantitative analysis of strong uniaxial texture using a March–Dollase approach

2013 ◽  
Vol 46 (6) ◽  
pp. 1877-1879 ◽  
Author(s):  
Emil Zolotoyabko
Keyword(s):  
Quantitative Analysis ◽  
Intensity Ratio ◽  
Preferred Orientation ◽  
Diffraction Peak ◽  
X Ray Diffraction ◽  
Rocking Curve ◽  
X Ray ◽  
Diffraction Peaks ◽  
Analytical Expressions

Interrelations between the degree of uniaxial preferred orientation and the intensities and widths of selected X-ray diffraction peaks are analyzed within the March–Dollase approach. Simple analytical expressions are developed which relate the degree of preferred orientation to the rocking curve width of the strongest diffraction peak or the intensity ratio of two diffraction peaks, one of them being originated in the preferably orientated atomic planes.

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