We have prepared pure ZnO, and Cu doped ZnO samples by varying Cu doping percentages and using the co-precipitation method. In the XRD spectra, after doping, the (002) plan show a shifting of around 0.06 degree, whereas the higher angle plane (101) show less shifting (0.02 degree). What may be the reason for that?
The peak shift in XRD is related to the structural changes !!
See the post:
https://www.researchgate.net/post/What-are-all-possible-reasons-for-the-peak-shift-in-X-Ray-Diffraction#:~:text=The%20peak%20shift%20in%20XRD,shrinking%20of%20the%20XRD%20peaks.
I know that the reason for peak shifting may be related to the change in the crystal structure. But, here the lower diffraction angle peak shows higher shifting than the higher diffraction angle peak. What may be the reason for such behaviour?
May be: local structural deformation by doping, lattice strain, ...
The resolution of d (d/delta(d)) will be higher in the lower two theta value or higher two theta value? if you can find the answer to this then you will find the answer to your question.
As for the ionic radius concern, Zn2+ is slightly larger than Cu2+. Thus, when you dope ZnO with Cu2+, it is expected that effective lattice volume will shrink or interplanar lattice spacing will get reduced. That is why peaks will shift to higher angle. Now, doping with different ionic radius also causes lattice strain, which will momentarily causes to peak broadening. Smaller crystal size also causes peak broadening, however size broadening is dominating in lower angle side and strain broadening is dominating at higher angle side. So, you have to carefully analyse both position and peak broadening. The type of strain and its distribution throughout the sample is also important, as inhomogeneous strain causes inhomogeneous peak broadening.
For more detailed analysis, you need to calculate the atomic positions through Rietveld refinements.
All the best.
Sathi Chatterjee , kindly refer to the XRD section of the following article, hope it answers your query:
Article Effect of Cu-N co-doping on the dielectric properties of ZnO...
Rietveld refinement will give the average structure only. If you want to find the actual structure you can carry out the Pair Distribution function measurement. I think it will resolve your problem.
@Manpreet Kaur, Could you please tell me how accurate the lattice parameters are given in table 6 of your manuscript? Because the c/a ratio is not systematically varying. For x=0.005 it is 1.6015, for x= 0.02 it is less than the value for x = 0.01 and finally it is 1.6019. Similarly the a and c values, there is no systematic. While carrying out you should have given the same atomic position of Zn for Cu with occupancy factor and similarly for N.
Dharmadoss Sornadurai , the variation you have observed is due to the formation of lattice defects and vacancies, it is highly rare to see consistent results, the variation observed has been explained in the paper with proper explanation.
Secondly, atomic positions will definitely differ, they cannot be similar, this occurs due to the difference in crystal radii, electronegativity values of the (Zn, Cu), and (O, N) atoms.
@ Manpreet Kaur, Could you send me the question and the concerned manuscript, I lost the track of it. Any how variation of atomic position randomly is a lattice defect. Second I don't understand what you mean crystal radii?
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