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Old Oct 29th 2018, 10:27 AM   #1
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crystalite size , grain size,particle size

What is the difference between crystallite size, grain size, and particle size?
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Old Oct 29th 2018, 11:09 AM   #2
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This largely depends on the context.
What is this question in connection with?
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Old Oct 29th 2018, 11:31 AM   #3
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Originally Posted by Woody View Post
This largely depends on the context.
What is this question in connection with?
I am studying about XRD technique,
Scherrer equation, FWHM. these three terms are related to it and I am confused about these.
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Old Oct 30th 2018, 03:26 AM   #4
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These are almost interchangeable terms.
The main difference is the (bulk) material which is being studied.
Then again which term is used is rather related to the term used by the industry which would most often employ this (bulk) material rather than to any scientific distinction.
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Old Oct 30th 2018, 10:29 AM   #5
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Originally Posted by Woody View Post
These are almost interchangeable terms.
The main difference is the (bulk) material which is being studied.
Then again which term is used is rather related to the term used by the industry which would most often employ this (bulk) material rather than to any scientific distinction.

I think we can differentiate them by their size?
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Old Oct 30th 2018, 11:20 AM   #6
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No, I don't think that these terms (deliberately) denote a size difference.

I am rather stepping outside of my knowledge area, but...

I think crystallite refers to materials that include (small) crystals within the bulk material.
Grain size is a measure (in metallic alloys for example) of the size of regions where one or another of the constituents dominates the mix.
Particle size is where the bulk material is formed where a powder has been compressed until it binds.

The XRD technique detects ways in which the fine detail of the bulk material is not entirely uniform.
The features it detects are all of (roughly) the same size
however in different materials the features will have been formed via different processes
and will be given different names.
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Old Oct 30th 2018, 12:20 PM   #7
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Originally Posted by Woody View Post
No, I don't think that these terms (deliberately) denote a size difference.

I am rather stepping outside of my knowledge area, but...

I think crystallite refers to materials that include (small) crystals within the bulk material.
Grain size is a measure (in metallic alloys for example) of the size of regions where one or another of the constituents dominates the mix.
Particle size is where the bulk material is formed where a powder has been compressed until it binds.

The XRD technique detects ways in which the fine detail of the bulk material is not entirely uniform.
The features it detects are all of (roughly) the same size
however in different materials the features will have been formed via different processes
and will be given different names.
to some extent, I got it now
thank you
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Old Oct 31st 2018, 05:21 AM   #8
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What is the difference between crystallite size, grain size, and particle size?
You are asking about the difference in sizes. Can I assume you know and understand what particles, grains and crystallites are? I have deliberately reversed the order.

Size in all three generally refers to a size range.

For particles, which may be compressed into a bulk material eg sandstone as Woody says. Or particles may refer to individual chunks eg a pile of sand particles. Here is a dificulty, probably why Woody asked for your application, since grains and particles are used interchangeably to describe the above materials. This is not very scientific, especially as grains also have a second more restricted meaning in chemistry/metallurgy. So for the grains of sand = particles of sand usage, the range of size is the most important thing. The variation of size is referred to as the grading. It is the grading that is important.

For grains in the chemical/metallurgical sense it is not (as Woody suggests) the composition that is important, but the orientation of the grains. Grains here are the result of crystals which are growing in different directions and meet at what are known as grain boundaries. These grains may have the same, similar or different compositions.
The important size parameter here is the average grain size.

Finally crystallites are imperfectly formed cystals, often an intermediate stage of some process, but sometimes formed by inclusion in a later process.
The crystallites are tiny in relation to the crystal sizes of the eventual material and of different composition.
An example would be tiny mica crystals within the feldspar crystals (which are properly formed) and may be within grains (if there are any) of a larger body of parent material (granite in the example). This time relative average sizes are important.

Does this help?
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Last edited by studiot; Oct 31st 2018 at 03:39 PM.
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