I have done powder XRD of samples and I have done fitting of XRD peaks by Gaussian function and calculated whole area of the sample. But I unable to calculate the integrated area of each peak including crystalline and amorphous peak. How to identify crystalline and amorphous peak? Kindly explain.

Hi Rajkumar

First you have to do fitting of XRD peaks by gaussian or lorentizan function. (origin software helps you, Other peak fitting softwares also available). Some peaks are due to Crystalline and some due to amorphous nature of the sample. you have to calculate the integrated area of each peak. Then % of crystallinity can be calculated as

% crystallinity = Area of crystalline peaks/(Area of crystalline peaks+amorphous peaks)

The XRD data provide you phase identification of the sample. the % crystallinity can be calculated if you know the intensity of total crystallization and partial crystallization XRD data. in my view you need a reference of fully crystallized data of XRD

Crystallinity can be determined with the aid of an internal standard. Typical internal standards include zincite (ZnO) and corundum (Al2O3). The procedure generally consist of mixing (well, ideally using a McCrone mill) a known quantity (10-50wt%, less if sample is more amorphous) of standard with your sample, and collecting the diffractogram of the mixture. Then the crystalline phases, including the standard, are quantified with Rietveld refinement. Based on the quantified value of the reference, compared to the known amount, the amount of amorphous can be estimated.

Examples:

1-) If you add 20wt% reference, and the quantification indicates 50wt% of this phase, that means (20*(100-50)/50=20)/(100-20=80) (25wt%) of the original sample is crystalline, and the balance 60/80 (75wt%) is amorphous.

2-) If you add 20wt% and quantify 30wt%, then the crystalline is (20*(100-30)/30=46.7)/(100-20=80), or ~58wt%, and the amorphous is (80-46.4=33.3)/80, or ~42wt%.

3-) If you add 20wt% and quantify 20wt%, then there is no amorphous (crystalline=(20*(100-20)/20)/80=80/80=1=100wt%).

Note 1: any unidentified crystalline phases (i.e. note quantified) will be included in the amorphous value. This means this method can also be used to obtain accurate values of phases of interest when an unknown phase is present. But if only the true amorphous content is desired, all crystalline phases should be identified.

Note 2: This method is less accurate for complex diffraction patterns where the original phases overlap with the reference peaks. So care must be used to choose suitable standards that have unique isolated peaks.

Further details and examples available in this reference: Snellings, R., Machiels, L., Mertens, G., Elsen, J. (2010). Rietveld refinement strategy for quantitative phase analysis of partially amorphous zeolitised tuffaceous rocks. Geologica Belgica, 13 (3), 183-196.

http://popups.ulg.ac.be/Geol/docannexe.php?id=2955

Dear Rafael Santos,

i have been prepared nanoparticles of one of organic compounds and done XRD ii got few sharp and few broaden peaks then my supervisor said that compounds is not pure crystalline nature so told me that calculate the % of crystallinity. i do not having any reference sample to compare.

dear Raj, if you talk about % crystallinity then you should have the way to distinguish between a crystalline and an amorphous state. For sure thermal analysis can tell you if there is some amorphous or not (as you will see the heat exchange due to crystallization). .This said, if you see sharp and broad peaks for the same compound then the material is not "amorphous" but you just have anisotropic broadening (perhaps due to anisotropic shape?). "Broad peaks" is a rather crude definition as you already indicate they are peaks and therefore you assume the stuff is crystalline. If you have something like three humps or halos then the stuff is probably amorphous. Besides using a standard to quantify the crystalline fraction, you can also use the trick of considering one phase as extremely nano (Le Bail proposed this for glasses long time ago): it is not completely correct (especially at low angle) but in this way the size effect try to reproduce the very short range interactions and thus the halos and you can then quantify the amorphous part using the Rietveld method.

Raj, the reference I mentioned is a material that is different from any phase present in your sample, and it is used in the calculation procedure I described, it's not meant for comparison with your sample.

In the clarification you presented, I am unsure if you have a single compound, or perhaps one (or more) crystalline phases, represented by the sharp peaks you see, and other amorphous phase(s). Have you eliminated the possibility that some secondary salts or other material formed during your nanoparticle synthesis? I am not familiar with a single phase having simultaneously sharp and broad peaks, although Matteo suggested this could happen due to anisotropy.

In case you have poorly crystalline phase(s), the degree of crystallinity can be estimated during Rietveld refinement, but if the phase is truly amorphous the accuracy is low with this methodology. Recently I attempted doing this for colloidal silica mixed with crystalline minerals, but I found difficult to nail the correct crystallinity value as it approached zero, and this had a large influence on the quantification result.

Dear Raj Kumar;

please read this article. your question is answers in it completely.

"Development of a mathematical expression for the variation of amorphization phenomenon during intensive milling of minerals"

http://www.sciencedirect.com/science/article/pii/S0301751609001537

Dear Rajkumar,

Mr Rafael Santos method is suitable, i just try improve upon that. At first, all crystalline phases present in a pattern has to be identified and quantified by Rietveld refinement method. Then, a known amount of internal standard has to added (which should not overlap your present peaks), from this powder again quantitative phase analysis by XRD, has to be done. Then amorphous phase qty (%)=100-Total sum of all crystalline phases. In this method one cannot distinguish amorphous mixtures. (this can be done if one knows the CIF model of amorphous phases.

Thanks to ALL for valuable suggestion

i didn't understand. how do i fit of XRD peaks by gaussian or lorentizan function?

and then how i get % crystallinity? would you please explain more? in XPowder softeware. thank you

I have done powder XRD of samples and I have done fitting of XRD peaks by Gaussian function and calculated whole area of the sample. But I unable to calculate the integrated area of each peak including crystalline and amorphous peak. How to identify crystalline and amorphous peak? Kindly explain.

u calculate the area using origin or if there is any characteristic peak for ur samples then calculated the area of that peak for all sample and with respect raw sample calculate the %crystallinity assuming as the raw has 100 % crystalline, or take the intensity of peak of characteristic for samples based on intensity also you can calculated the % crystallinity.

Since the early twentieth century diffraction (ICDD) are characteristic of crystalline solids.

Quantitative analysis by XRD of the phases present in a polycrystalline material is based on the principle that a phase integrated intensities are related to their abundance in the mixture (Klugg & Alexander, 1974).

Through various programs Rietveld can quantitatively analyze the crystalline phases. Absolute weight percentages of each of the phases is 100%. If amorphous phase or unidentified crystalline impurities are present in the sample, these percentages can be determined by adding a known amount (e.g., around 20% by) of an internal standard.

The difference between 100% and the total of absolute abundances represent the amount of glassy phase.

 Can any one  please, give more details about that or recommend a specific program to determine or measurement that. 

Please, can anyone calculate the amount of crystalline according to this graph.

https://www.researchgate.net/post/How_can_we_calculate_degree_of_crystallinity_from_an_XRD_spectra#59a700735b495203cd5790a7