Dear Piotr,

Thanks for your answer.

I agree, but what is the effect of the different kaplha radiations. for example. if material A is excited by Copper k alpha radiation which is nearly 1.4 and if same material A is excited by Cobalt Kaplha radiation source which is almost 1.7. peak shifts will occour in both cases like in case A if thepeak is at 20° in case B peak will be at 21° why does this happen?

but the over all spectra remains the same.

Thanks

Depends what you mean by "different"

Some XRD machines can be more sensitive than others, so if an older version of XRD machine shows mostly amorphous powder with no clear peaks, new machines can give you a good resolution of peaks, or show some peaks that older versions did not show. However, the strong peaks should be there with just different intensity. Ignore the intensity because it is arbitrary unit. The 2theta angle is more important and it should be the same.

It may also happen that the whole spectra is a little shifted to the left or right, this really happens because of the average height of the surface (for powder) is not at the recommended height, so you need to be careful to flatten the powder surface at exactly the height it must be. It is not easy to make flat surface at the right height if your powder is coarse. Grinding your powder, especially with a high energy ball milling technique can change the composition (adding impurities etc.), as was said above.

However I think that grinding in a mortar by hand should not generally change the peaks unless your powder can absorb humidity during grinding time, and change the powder composition.

Edit: I see your interest is more in the type of radiation, sorry if my answer was not directly related.

I totally support Dr. Hobosyan point. I would ad one more reason that may affect. that is the calibration of instrument. make sure the instrument is calibrated well and works well.

Thanks Mkhitar

I totaly agree with your answer. but the situation here is different. i want to know why does the 2 theta changes. I had done exactly as you said, all the parameters were same.

the only thing is i excited my sample with a copper kaplha source and cobalt kaplha source. so if by copper source, one high intensity peak is lets suppose at 20°, by cobalt k aplha source the peak shifts to 21° why does this peak shift happens?

Best

Shoaib

Thankyou Artavazd,

I also agree, but if you use the computer simulations to generate an XRD spectra of a pure crystal structure. still you will see some peak shifts because of different Kalpha sources. in my case Copper k alpha and Cobalt kaplha source was used,

So what the reason behind this peak shift? does it still depends on the callibration or the source has an effect on the excitation?

Best

Shoaib

The reason might be how exactly you are converting from one to another, d spacing should be the same, as Artavazd said, calibration is important as well as see similar questions that addressed the peak shifts here:

https://www.researchgate.net/post/How_can_I_convert_the_XRD_pattern_taken_using_Cobalt-K_alpha_to_Copper-K_alpha

And

https://www.researchgate.net/post/How_to_change_XRD_result_with_Cobalt_target_to_equivalent_result_with_Cu

Here is one most likely potential reason, alignment!

https://www.researchgate.net/post/Is_this_a_reasonable_way_to_eliminate_effects_of_sample_surface_misalignment_with_the_diffractometer_axis_Theta-2Theta_Diffractograms

The results for the x-data diffraction should be the same for the same X-ray radiation for example Cu k-alpha. The intensity may differ but not relative intensity since all these parameters are crystal structure dependent

again we ahold know what is the exact different you mean

I have a feeling that the question is about theoretical implications of different wavelengths rather than practical experimental considerations - if not, and this seems trivial, please ignore.

Peaks appear when the Bragg condition is satisfied; i.e. radiation of a certain wavelength is incident on layers of atoms with a certain spacing at a certain incidence angle. If any of these parameters (wavelength, interplanar spacing, incidence angle) changes, the peak will shift to some other condition where Bragg's law is satisfied. Therefore, when you change the source i.e. the wavelength changes, the peak will shift to a different incidence angle (since the interplanar spacing is a material property and not an experimental parameter). I am intentionally not adding the mathematical formulation because this is something that should be read up.

Nevertheless, an intuitive analogy may be the colours you see reflected off a CD; different colours (wavelengths) are visible when you change your viewing angle (incidence angle, or position of peak in XRD). The position of pits on the CD (=interplanar spacing) remains the same.

Please ignore if this is not what you were looking for! If it is, however, then do consider reframing the question to ask about different sources rather than different instruments - that changes the meaning entirely. Also I believe XRD spectrum is incorrect because we are using a single wavelength (not a spectrum). Pattern may be a better alternative.

"Also I believe XRD spectrum is incorrect because we are using a single wavelength (not a spectrum)."

Even in a synchrotron it is only a "near Delta function" depending on the quality of the beam conditioners and the sensitivity of the detector used :-) In most other instruments there is always a sort of remnant "spectrum" of wavelengths after the beam conditioner. Some at detectable levels others not. This is the reason for using the "instrumental profile" to deconvolute Nano structural parameters correctly. The argument whether to call it a spectrum or diffractogram or profile is only a recent one. The Bragg Spectrometer is something you ought to study a bit :-)

Thank you for educating me! :) Conventions do change, but it's good to learn the history as well. Certainly you are right that we never have truly monochromatic radiation.

Sure! They do! I mean, "Conventions do change". Just examine the words "good" and "bad". Milleniels' use of these words has virtually blurred the difference. That would be a whole other RG discussion on semantics, I suppose. However, in my opinion, the use of the word "spectrum" or "spectra" to describe Bragg profiles oughtn't be so strictly enforced despite changes :-)

I think that the X-ray diffraction peaks of a crystalline compound (material) should give the same diffraction angles, even when moving from one XRD instrument to another, so the same dhkl reticular distances that allow us to know the crystalline structure and these parameters. On the other hand, I do not believe that the change of the anti-cathode (source of the device) will change the positions of the RX diffraction peaks.