can anybody clearly explain me reasons for broadening of XRD peaks.
Thank you in advance
Broadening of the XRD peak can arise from 3 possible reasons: instrumental broadening, strain broadening, and/or crystallite size related broadening. Any basic XRD text (e.g. Bragg or Alexander/Klug) will explain the reasoning.
I concur with the previous answers to broadening of the XRD pattern. To add to the previous references, Introduction to X‐ray Powder Diffractometry by Jenkins and Snyder is a great introduction/intermediate level text to get started.
Cheers!
Dear Naresh Kali,
Please go through the article: Article Applicabilities of the Warren-Averbach analysis and an alter...
Thank you Alan F Rawle , Eleanor Bakker
you gave me nice information.
1. what is meant by strain broadening and instrumental broadening?
2. Can you provide any mathematical relations apart form Debye Scherrer equation to support these statements
thank you in advance
strain broadening is simply either stretching or squeezing the crystal lattice under compression/tension, so plane spacing deviates from ideal and so does the peak. Instrumental broadening is simply because no x-ray radiation has infinite intensity at a particular wavelength and zero intensity infinitesimally small away from that wavelength (the x-ray lines can be few picometers broad due to thermal vibration of atoms, doppler shift of x-ray frequency emitted by fast-moving 'evaporated' atoms so on so forth. and of course, thermal vibration implies all atoms of any diffracting plane must be jumping to and fro about the average position of plane. that adds to planar spacing variation and XRD peak broadening. Also for finer crystallites, lattice size is much less than "infinite" compared to lattice parameter, so there is no atomic parallel planes "far below" the top reflecting plane that would completely neutralize a reflection at angle only minutely different from permissible angle.
Sumit Bhowmick , Naresh Kali experimental broadening is mainly due to the finite linewidth of the used X-ray radiation (natural linewidth), plus the divergence of the beam and the acceptance of the detector.
Some more details? First of all, the radiation is not parallel, exept maybe radiation from a synchrotron, so that the incidence angle on the sample varies depending on the position on the sample, leading to different geometries and a "modified" diffraction thereby. The same applies for the detector, that accepts radiation through a certain slit, with a related divergence. Both effects add up and lead to instrumental broadening of the Bragg peaks. Depending on the slit size etc, the effects can be minimized, but they are always contributing to the detected diffractograms! Usually, broadening from the sample and the experimental setup have to be deconvoluted by applying some mathematics ... Hope this helps, best regards, Dirk
The broadening in the peaks of the XRD patterns arises due to the finite size of the crystals. If one has crystal of infinite size, the peaks in the XRD pattern will appear as very sharp and as size get reduces peak broadening increases.
Naresh Kali
Take care - there is no 'Debye Scherrer equation' (your question 2 about 9 hours ago). IMHO, the value of the constant in the Scherrer equation is semi-witchcraft (Scherrer derived 0.89 and Bragg derived 0.94 - math dependent. There are many other derivations to ridiculous numbers of decimal places. A constant of ~ 0.9 isn't really that precise and means that quotation of anything after the decimal place in nm is debatable. However we retain the equation for convenience and historical reasons). Williamson-Hall and Rietveld are likely to be significantly better alternatives in providing more information. See also: https://www.researchgate.net/post/What_are_the_limitations_of_Debye_Scherrer_formula
The broadening of the XRD peaks, when the FWHM values decrease and its affects the intensities of the peaks where we can say the crystallinity of the films or materials is decreasing.
Please pay close attention to all of Steven Van Petegem's answer. Pay particular attention regarding "strain" broadening. Inhomogeneous strains result in broadening, homogeneous strains shift peaks.
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