In the XRD pattern of Fe, splitting is observed in (110) plane. Even the standard cif file shows this splitting. Also the standard data assign both these peak as (110) plane. I observed the same in the XRD patterns of FeCo and FeNi. (However, depending on synthesis parameters, sometimes single peak without any splitting is also observed) But this splitting is neither reported nor explained in the literature as far as I searched.
The peak splitting for Fe (110) plane is attached here along with data table obtained from standard cif using crystallographic open database (http://www.crystallography.net/cod/search.html).
It will be very helpful if anyone kindly explain or provide references for the same?
Dear Kavita Kumari ,
this splitting is due to the quite limited monochromaticity of the x-ray radiation in use.
The Cu K-alpha line is a doublet line having a wavelength of about lambdaK-alpha1 ~1,5406 A and lambdaK-alpha2~1,5444 A.
According to the Bragg law, an increase of lambda will increase the Bragg angle. Thus the diffraction peak due to the K-alpha2 line will be at larger 2theta(s) compared to the one caused by the K-alpha1 line.
Please check the angular positions of the peaks according to the Bragg law; you will see a quite perfect match.
The peak splitting (delta2theta) increases as the 2theta angle increases; this is due to the decreasing slope of the sine function in the Bragg law when going to larger 2theta.
The intensity ratio of K-alpha1/K-alpha2 of the primary radiation is close to 1:1/2. This can be also clearly seen in your XRD pattern.
The visibility of the peak splitting however depends on the width of the diffraction peak; e.g. on the instrumental boadening, on lattice defects, lattice strain, but also on the crystallite size(s) of your sample, which depends on the kind of sample preparation. For sufficient broad peaks you will not see such peak splitting.
Please see for example around page 14 of:
http://prism.mit.edu/xray/documents/5a%20Estimating%20Crystallite%20Size%20Using%20XRD.pdf
(you may open that document in a separate window...; if it does'nt work, I will send you that pdf via RG messenger...)
Best regards
G.M.
Dear Gerhard Martens
Thank You very much for the well described answer. This was very helpful in understanding my doubt about the peak splitting.
Thank you so very much.
Dear Kavita Kumari ,
In addition to the Gerhard Martens an answer, I would like to add following reasons.
The splitting may occurs due to the satellite peaks or crystal twinning. First identify the which splitting had been occurred.
Twinning in bulk crystal is a big problem, to remove it is another challenge to crystal growers. However, twin growth occurs during thermal stress of crucible, therefore, you should try to eliminate the thermal stress during crystal growth process. Only low angle twin (
Dear Dattatray Gadkari
Thank you very much sir for providing more insight about my query. I observed the peak splitting in the standard cif file and the splitted peaks are assigned the same reflection plane (110) as can be seen in the file that I have attached in my question. In my case, my samples are nanostructures and the peak is not exactly splitted but broad profile is observed containing multiple peaks. Therefore, after ruling out the formation of single phase with (110), I assumed that my samples either possesses more than one phase or a completely different phase.
Now, I think that twinning may also be present in my samples. I will analyze from this point of view also.
Thank you very much sir for your kind help.
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