# What is particle size, crystalline size, grain size?

What is the difference?

What are the instruments used to find the size?

What are the instruments used to find the size?

What is the difference?

What are the instruments used to find the size?

What are the instruments used to find the size?

## Popular Answers

Matteo Leoni· Università degli Studi di TrentoYou can measure the size along any direction.. remember that if you impose a certain average shape you can calculate the whole diffraction pattern. The distribution effects can be somehow decoupled but must always be considered as they are the responsible for the smooth shape of the peak.

For the less expert.. the diffraction peaks from a sphere in reciprocal space are the Fourier transform of 1-3L/(2D)+L^3/(2D^3) where L is the variable to be transformed and D is the diameter of the sphere. Try plotting it and you'll see some ripples appearing. They cancel out if you have a distribution. Plus you can test Scherrer formula ;)

PS to add a note to Kai's: believe me when I say that Scherrer equation is one of the most ABUSED equation in the field of X-ray diffraction....

Kai Fauth· University of WuerzburgSelvalakshmi, it is honourable that you ask the way you do unlike many others. For simplicity, I'd recommend you to to the same as to Youssef. I am sure you will readily find those threads.

## All Answers (14)

Nagbasavanna Sharanappa· Gulbarga UniversityParticle is minut object with a cetain size and shape. Macroscopically it is very small but microscopically it ontains number of olecules and atoms.

Particle size:It is size of individual Particle, determining absolute particle size is very difficult.

The crystallite size is the average size of a coherent scattering domain (perfect arrangement of unit cells or perfect crystal). The following Scherrer's formulae is using for crystallite size,

Crystallite size (nm) = kl / FWHM (cos q)

The term crystallite have been usually used by physicists and chemists, while grain size is mostly used by metallurgists.

You can easily findout the above by XRD, SEM, AFM , Particle size analyser(Horiba Company Japan)etc.

Better you refer the book Element of X-ray diffraction by W.D. Cullity.

Selvalakshmi Thangaraj· National Institute of Technology TiruchirappalliGrain size has grain boundary to define the size. similarly does particle size have any boundary?

Yuriy P. Gnatenko· National Academy of Sciences of UkraineAucun Jwane· University of StrasbourgKai Fauth· University of WuerzburgSelvalakshmi, it is honourable that you ask the way you do unlike many others. For simplicity, I'd recommend you to to the same as to Youssef. I am sure you will readily find those threads.

Hamid Farahani· Putra University, MalaysiaVasyl Peter Kladko· National Academy of Sciences of UkraineThat is the size and shape of the object does not define its internal (atomic) structure.

In addition, you can measure the size of the coherent domain using XRD only in a certain direction. In addition there is the size distribution. Most people are probably using Scherrer formula for estimating the "average crystallite size" for crystalline material, do not understand what they receive value is not the average size distribution areas.

Matteo Leoni· Università degli Studi di TrentoYou can measure the size along any direction.. remember that if you impose a certain average shape you can calculate the whole diffraction pattern. The distribution effects can be somehow decoupled but must always be considered as they are the responsible for the smooth shape of the peak.

For the less expert.. the diffraction peaks from a sphere in reciprocal space are the Fourier transform of 1-3L/(2D)+L^3/(2D^3) where L is the variable to be transformed and D is the diameter of the sphere. Try plotting it and you'll see some ripples appearing. They cancel out if you have a distribution. Plus you can test Scherrer formula ;)

PS to add a note to Kai's: believe me when I say that Scherrer equation is one of the most ABUSED equation in the field of X-ray diffraction....

Yuriy P. Gnatenko· National Academy of Sciences of UkraineVasyl Peter Kladko· National Academy of Sciences of UkraineMatteo Leoni· Università degli Studi di TrentoAucun Jwane· University of StrasbourgMatteo Leoni· Università degli Studi di TrentoG. Dezanneau· Ecole Centrale Parissome few additonal things here:

- light scattering: this gives you the size of diffusing objects then most often it is related to particle size

- XRD: this gives you the coherent scattering domain size. This can be hkl dependent and can be strongly affected by stacking faults or other defects.

Sherrer is a rough method but can be used in case of non strained nanoparticles.

(Warren-Averbach is an old method that in principle allows you separating size-strain effects). Now, most of rietvled codes include different models/approaches to treat size-strain effects, in which the convolution between instrumental resolution and size-strain effects is done directly (contrarily to sherrer approach).

- TEM : this gives you a picture of coherent domain (by perfomring filtered Back FT). so the size is that of coherent domain.

- SEM: this would give you the particle/grain size in powders or the grain size in ceramics (after thermal teching or fracture). Some methods exist to extrapolate the 2D grain size as obtained from images to 3D images. (interception method)

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