Why is XRD baseline different for different samples? i have done XRD for NiZnFe2O4 and for CoZnFe2O4 nanoparticles, for first one the baseline starts from 1500 and for second one from 1200. please explain why it is not started from Zero. tahnks
Ok, firstly you need to remember that the intensity values are arbitrary units and will differ from equipment to equipment and sample to sample.
In simple words, there could be many reasons for the difference in intensity values;
1) Different materials (you can not get exactly same intensities for different materials, due to difference in structural features,
2) Difference in particle size and morphology distributions of your samples,
3) sample preparation (you can have different values for exactly the same sample if not prepared properly,
4) background noise possibly due to contamination/ moisture and so on,
Having said all this, you no need to worry about this difference in your two different materials XRD, because you can not compare them with each other and it doesn't mean anything anyways,
The relative intensity of 1 sample helps you to see the peaks intensities of that sample relative to each other.
For more details and to understand what it means in terms of mathematics/ chemistry, please read the Brag's Law and other basic XRD concepts, its easy!!
Wish you all the best.
Rehan
Dear Ashfaq,
What are the units for 1500? do you mean to say that 1500 on (y-axis)? which is the intensity value or ...?
Can you please share your XRD graphs for further comments...
Rehan
Ok, firstly you need to remember that the intensity values are arbitrary units and will differ from equipment to equipment and sample to sample.
In simple words, there could be many reasons for the difference in intensity values;
1) Different materials (you can not get exactly same intensities for different materials, due to difference in structural features,
2) Difference in particle size and morphology distributions of your samples,
3) sample preparation (you can have different values for exactly the same sample if not prepared properly,
4) background noise possibly due to contamination/ moisture and so on,
Having said all this, you no need to worry about this difference in your two different materials XRD, because you can not compare them with each other and it doesn't mean anything anyways,
The relative intensity of 1 sample helps you to see the peaks intensities of that sample relative to each other.
For more details and to understand what it means in terms of mathematics/ chemistry, please read the Brag's Law and other basic XRD concepts, its easy!!
Wish you all the best.
Rehan
Good answers from M Rehan. I would just add the obvious - that since the difference between your samples is Ni versus Co, the differences in "baseline" (by which I am assuming you mean background) would be primarily due to differences in scattering power, absorption, and fluorescence of these elements for the radiation (Cu k-alpha ?) selected.
Depending on your set up and what kind of diffractometer you have, there can be different fluorescence backgrounds, or perhaps differences in the bremstrahlung.
Is it a theta - two theta Bragg-Brentano diffractometer? I newer design which makes use of an energy dispersive detector along with a sample that turns in an angle? There are too many different types of x-ray diffractometers to enumerate here.
Thanks Edward for your endorsement, I listed the few possible reasons for basic understanding, but I also believe the main reason to be the background effect due to both samples being different material.
Thanks
Raised background levels can also be caused by amorphous material in a sample.
It would be helpful to see the two diffractograms presented together.
Again, what kind of diffractometer do you have? Do you have a copper anode? With a copper anode the wavelength of the copper K alpha line is 1.54 Angstroms and the wavelength of the copper K beta line is 1.38 Angstroms. If you have an old fashioned instrument you would have a Ni filter, The K absorption edge of Ni is at a wave length of 1.49 Angstroms, slightly lower in energy than the copper K alpha but higher in energy than the copper K beta. The filter then serves to remove almost all of the copper K beta, greatly simplifying the interpretation of your data. However, Ni atoms in the sample are not excited to higher K states by the Characteristic K emission of copper. However; cobalt atoms are excited to higher K states by the copper K alpha line. More modern instruments would probably have some means of instrumentally monochromatizing the output from your tube.
But if, as I suspect, you are using a filter in concert with a copper anode, probably the only solution would be to switch (carefully, because they can take less power input) to a cobalt anode and then change from a nickel to an iron filter.
I agree with the above explanations.
Take in account also the volume of the sample which may be different every time. Simply try, if you can, with the same material loading different amounts of material and you should have a proportionality of some kind.
Using two different graphite powder samples (different average thickness mostly), for example, I had different backgrounds from low to high diffraction angles.
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