I did the calculation using Scherrer's formula (D= Lambda/ Bita*cos(theta)). FWHM calculated from the XRD plot using Origin pro (multiple peak fit to deconvolute overlapped peaks and peak analyser to get the FWHM).
The trend of crystallite sizes are found to be decreasing with thickness.This contradicts the SEM images. Though the sample peak intensity is increasing as film thickness increases.
I would like to ask how the crystallite sizes are decreasing with film thickness even though the sample peaks are getting sharper with increasing film thickness. Is there any mistake I am making in the calculation??
Dear Dr. Seeraz Nawaz
Have a nice day and good times
The attached paper study the structure and crystal imperfections of some compositions.
They may help you.
Good luck
https://www.researchgate.net/publication/300093556_Microstructural_characterization_of_Al-Mg_alloys_by_X-ray_diffraction_line_profile_analysis_------_IJAR-4360_--_9-4-2016?ev=prf_pub
https://www.researchgate.net/publication/277004252_Microstructure_and_crystal_imperfections_of_nanosized_CdS_x_Se_1-x_thermally_evaporated_thin_films
https://www.researchgate.net/publication/277010463_Crystal_imperfections_and_Mott_parameters_of_sprayed_nanostructure_IrO2_thin_films
Data Microstructural characterization of Al-Mg alloys by X-ray di...
Article Microstructure and crystal imperfections of nanosized CdS x ...
Article Crystal imperfections and Mott parameters of sprayed nanostr...
Whit SEM you are calculating particle size, with XRD you can calculate cristallite size.
Dear Nawaz,
You sould note that the Scherrer equation is limited to nano-scale particles. It is not applicable to grains larger than about 0.1 to 0.2 μm.
All the best.
SAXD technique is better than WAXD. Debby-Scherrer is good for your calculations
Dear Seeraz,
Scherrer equation is not very precise. It does not take into account the device related broadening of the peak which is different for each XRD device. It is better to use the “Warren-Averbach-Methode”. On the other hand, you will not obtain crystal sizes by SEM, what you see is just morphology – as already mentioned by the others. You could try to prepare a TEM sample. If you are lucky, you can also be successful with an polished and etched cross section in SEM. If I find the file (there were many HDD Crashs in between), I will send you my diploma work which deals with exactly your problem.
Regards,
Andreas
Dear Seeraz
as you say the sample peaks are getting sharper with increasing film thickness. This indicates that the crystallinity of the films is going to be increased and the cystallite size will be increased.
Dear Seeraz
First of all, the increasing of the peaks is a function to the density of the planes in the unit cell, might be, there is increasing in the intensity with thickness, it is possible because there is increasing in the polycrystalline phase. the application of Scherrer formula must be applied for all peaks accumulated, by draw the relation between (Bita) and the inverse of (Cos theta). you can conclude the straight line its slope showed the particle size as overall.
secondly, you can use Willmson formula to find particle size batter than the Scherrer formula, because it gives more details on the lattice strain.
yes the results of Scherre formula is not agree with the SEM for many reasons
1] SEM used to find the grain size not particle size
2] even if, there is a particle size appeared. the measureing is individual in acretain region whaere as the Scherrer foruula give us accumulate data.
Regards
Prof. Dr. Emad Al-Shakarchi
I’d like to add that broadening of peaks is not a function of grain size only. Stress and dislocations influence the plane distances as well. Consequently, the measured profile is a convolution of grain size, stress, dislocation density and the device profile (which can be eliminated by measuring a standard sample). To get a real value for grain size, a fourier transformation of the physical profile is required. A simple equation, such as the Scherrer equation, is only valid under ideal conditions. Nevertheless, in many cases the values obtained are not that far from reality – don’t ask me why. The problem is: you never know if you have such a case or not J.
Regards,
Andreas
I think this link can help
http://www.instanano.com/characterization/theoretical/xrd-size-calculation/
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