Crystallinity has to do with what portion of the diffracting volume is crystalline (ordered) versus amorphous or other phase (disordered). This may be determined by computing the integrated intensity of the crystalline diffracting component while that of the amorphous phase is also computed by determining the integrated intensity of the amorphous diffracting phase. In order to do this correctly you would need to deconvolute the individual component's diffraction signal correctly. This usually implies the need for correct modeling.

Crystallite size has to do with the coherent diffracting domain size in the crystalline constituent. This is related to the defect density of the crystalline component in the composite.

Generally, the process of annealing causes increased crystallinity in the amorphous phase while the crystalline phase experiences a dissipation of strain by dislocation movement, annihilation and coalescence. There are other mechanisms at play as well.

"crystallinity and crystallite size are same for polycrystalline sample"

NO! One is a dimensionless fraction while the other has physical dimensions respectively :-)

Dear Devi Ji,

With increase in heat treatment temperature crystallite sizes get increased. As we increase the heat treatment temperature diffusion of the crystallites increases which causes overall increase in crystallite size. However, crystallinity of the system depends on the cooling rate of the system from the heat treatment temperature to room temperature. If system cooled (in a controlled manner) slowly, then we can observed an increase in crystallinity of the system. If we cool the system very fast, then we can get sample with an amorphous nature. I hope it will be helpful for you.

Thank you Dr Dinesh for the detail explanation.

If a sample is heated at different temp. say 500 and 1000 degree celsius under same cooling rate, then ?

With regards

In such case, you can except increment in both parameters: crystallinity and crystallite sizes.

Okay, thanks Dr Dinesh Ji

With regards

Crystallinity has to do with what portion of the diffracting volume is crystalline (ordered) versus amorphous or other phase (disordered). This may be determined by computing the integrated intensity of the crystalline diffracting component while that of the amorphous phase is also computed by determining the integrated intensity of the amorphous diffracting phase. In order to do this correctly you would need to deconvolute the individual component's diffraction signal correctly. This usually implies the need for correct modeling.

Crystallite size has to do with the coherent diffracting domain size in the crystalline constituent. This is related to the defect density of the crystalline component in the composite.

Generally, the process of annealing causes increased crystallinity in the amorphous phase while the crystalline phase experiences a dissipation of strain by dislocation movement, annihilation and coalescence. There are other mechanisms at play as well.

"crystallinity and crystallite size are same for polycrystalline sample"

NO! One is a dimensionless fraction while the other has physical dimensions respectively :-)

Dear Dr. Ravi Ananth Sir,

Thank you so much for comparing and contrasting the two terms very nicely in detail. The concept of dimension gives a very clear view.

I would like to know a little bit more regarding the crystallinity (as crystallite size can be calculated using Scherrer relation from the XRD data, it is clear to conclude).

May I compare (conclude) the degree of crystallinity of the same sample annealed at 2 different temperature (provided similar condition and same phase) by just directly comparing the integrated intensity of highest peak taken for each sample? If yes, the following 3 cases may arise (I think):

1. Integrated intensity of lower temp. < Integrated intensity of higher temp. (higher temperature has higher crystallinity)

2. Integrated intensity of lower temp. ~ Integrated intensity of higher temp. (almost same degree and hence other mechanisms)

3. Integrated intensity of lower temp. > Integrated intensity of higher temp. (lower temperature has higher crystallinity, any possibilities/ possible reason?)

So, out of these three cases, which one is possible/ impossible/ most favorable in general or does it is specific for samples or any other conditions?

Your kind answers and suggestions are most welcome.

With best regards

Chitra

If we have nonisotropic size of particles (clusters, domains at all) we get non ICDD card diffraction curve - the same position of peaks, but no intensity relatations. Usually, during heating those particles aligned and fitted along one or more crystallography directions and we see new intensity relationship.

Thank you so much Dr. Michael Sir for sharing an important information. The said information is a new information for me. So, I would like to request you to please provide some relevant sources regarding it so that I can get some ideas about it.

With best regards

"as crystallite size can be calculated using Scherrer relation from the XRD data, it is clear to conclude" No! Not unless you completely neglect the effect of strain on the integrated breadth (not FWHM) during annealing. You'd need to use the W-H (Williamson-Hall) method to separate the strain and size effects.

http://pd.chem.ucl.ac.uk/pdnn/peaks/sizedet.htm

Do post your XRD data for the best feed-back from RG and test each of your hypotheses experimentally to find the correct answer. It all depends on your specimen material. What is it? Post all the juicy details including chemistry and all prior processing conditions :-)

Dear Dr. Ravi Sir

Thank you so much for the response and suggestions.

Sir, I do agree and satisfied with all your answers and concepts. The calculated crystallite sizes (using Scherrer equation) were around 10nm and 53nm for as-prepared and sintered (1200oC) Mn-Zn ferrite, so I concluded an increase in crystallite size. Please see the attached file for the XRD patterns. Unfortunately, the measurements were done by different instruments, and hence, I haven’t compared it directly. Currently, due to insufficient data, I’m just roughly studying the general observed trend and this lead to my hypotheses. I’m really sorry for this (presenting only my hypothesis and no data). I will surely follow the proper steps you have suggested in my future works.

Sir, I was searching for the answers to WHY but additionally I have also got the answers to HOW from your response and suggestions. Thanks a lot for the all the useful information, valuable advice and the attached files.

With best regards

Chitra

I agree, Ravi Anant, you're right.

"the process of annealing causes increased crystallinity in the amorphous phase"

Scherrer against W-H (Williamson-Hall) - a battle of models.

In my practice, I found that (sometimes) the Sherrer method applied to full massive of XRD peaks showed a large scatter of domain sizes (wide and narrow FWHM).

If we take several orders of peaks, for example: 100, 200, 300 or 111, 222, 333 etс, we see a different size, but a small size scatter of 100 and 111 direction (narrow FWHM in one direction and wide in another).

- It is battle of physics vs mathematics :-)).

Thus, if the domains (after annealing) are located one direction, the repeatability factor for some direction increases and the intensity of the reflex in this direction increases

Thank you Dr. Michael Sir for sharing personal experiences and important concepts.

With best regards

Normalize using the integrated intensity beneath each respective diffractogram and then superimpose them on each other to compare. Index your reflection. Use Reitveld. Beware of limitations of the conventional Scherrer approach. Learn about WPPM (Scardi, Leoni et al)

Post your XRD data as Excel file so others might help you too :-)

I also suggest you include additional relevant topics up top in your question to share with a larger audience of XRD experts on RG. Refer to this discussion noted below to see some other topics to include. You may include up to 15.

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

https://www.linkedin.com/groups/2683600/2683600-6359332934163451905