Unfortunately on the site people look at the last 2 answers they see and then they propose their own answers.And of course people prefer the answers they understand versus the correct ones. This does not mean I give correct answers. I mean that some answers have already been given, some wrong ones have already been discussed and people keep reiterating. If you check the full discussion you find also this answer I gave 30 days ago. It can give you an idea why things are complicated:

grains can be crystalline or amorphous. Coherently scattering domains (I don't like to call them crystallites as there is no universally accepted definition for this term) are the crystalline regions of material that scatter coherently (and in general they show no coherence with the neighboring ones). They are single crystal in nature (but they are in a powder as defined in the diffraction sense). A grain can contain multiple domains (consider e.g. two domains highly misoriented each other). The grain and the domain size are seldom the same in a polycrystalline aggregate but can be the same in a proper nanosized powder

30 days ago

A crystallite is long range order of atoms. But a particle is often has more than one crystallite, but not necessarily. XRD gives the crystallite size, not particle size. However, some time we find good agreement between particle size obtained from TEM and XRD analysis, especially in nanoparticles. This may be the case where the nanoparticles are single crystalline.

agree with Tamilarasan Palanisamy

have a look at similar questions that appeared in RG several times. There is NO such thing as "Debye Scherrer" formula. There is Scherrer formula though and it does NOT give the average size of "crystallites". From XRD you can in any case calculate the size of the coherently diffracting domains. You can guess the same information from TEM, but you can hardly compare XRD with DLS data unless each particle is composed of one domain and they are well separated

But what about grain size? As a particle can be made up of many grains separated with grain boundaries. How grain size differs from crystallite size? If grains and crystallites are same then grain boundaries are the boundaries separating crystallites. Please need more clarification

Hi Tarun,

We can see grains by SEM easily. But the crystallite is somewhat theory based which is perfect single crystalline. We can not compare these two things. At grain boundaries there is perfect disorder while within grain slight change in order can exist or simply does therefore many crystallite may be there.

I think so....

grains can be crystalline or amorphous. Coherently scattering domains (I don't like to call them crystallites as there is no universally accepted definition for this term) are the crystalline regions of material that scatter coherently (and in general they show no coherence with the neighboring ones). They are single crystal in nature (but they are in a powder as defined in the diffraction sense). A grain can contain multiple domains (consider e.g. two domains highly misoriented each other). The grain and the domain size are seldom the same in a polycrystalline aggregate but can be the same in a proper nanosized powder

What you calculate from XRD patterns based on Debye Scherrer's formula is the grain size or cristallite which are approximately the same.

What you get from DLS or other size distribution methods like that is particles size and have basically nothing to do with Grains size or cristallite size. What you have to know is that particle size is definitely larger or in some cases equals the grain size. As every particle contains number of grains inside or for the latter, the particle is containing only one grain( or namely the particle is single crystal as Matteo mentioned in some NPs)

This is can be Little though when you ask about the TEM images!! A TEM image taken from can simply show particle size. Also if you take that TEM image properly, it can represent the grain structure inside a particle or bulk material. I recommend you to ask your question or problem more specifically, providing some details about the sample and how the TEM is taken to get a better response.

If the particle or grain is a single crystalline that means all atoms are in same orientation and there is no grain boundaries (zero dislocations). But if you have poly crystalline or a mixture of crystalline and non-crystalline (glassy) orientation, here we have to take care about grain boundaries. So if the grain size is 10 nm the grain boundary is not less than 1nm and if the grain size increased the grain boundaries (GB) increases as well, therefore, GB plays an important role in the material proprieties. This is because GB or disorder or dislocation areas makes the crystallization differ in that region and new crystals like to nucleated on these areas where free energy is low and hence form poly crystalline not 100% single crystalline grains.

dear Hassan, my suggestion is to write what you are 100% sure about (because you can demonstrate it). In fact the number of errors present in your sentence:

"What you calculate from XRD patterns based on Debye Scherrer's formula is the grain size or cristallite which are approximately the same."

is amazingly large!

once again: THERE IS NO DEBYE SCHERRER FORMULA. The formula is ONLY due to Scherrer. By looking at the line profile you don't get information on the grain size, but you can get information on the size of the coherently scattering domains. Scherrer formula gives a size value calculated under very special conditions: that value in 99% of practical cases is NOT the average domain size (i.e. the first moment of hte size distribution). The domain size and the grain size are, within measurement errors, the same only when each grain is represented by a domain (i.e. in a true nanocrystalline powder).

The big risk of writing something we heard or something we read, but we do not master, is that other people will get wrong information. And unfortunately still a lot of people in 2013 DON'T KNOW what they are doing when they analyze X-ray data (I guess this is the same in most fields).

The answer of Majid shows some interesting elements. However there is some basic problem there. A monocrystalline particle corresponds to a grain and also to a domain and it has a surface that, i the end, is the analogous of half grain boundary. The structure of grain boundaries is still not 100% understood and I would not be sure that for a 10nm particle the boundary region is 1nm. If you use XRD line profile analysis to get the size information you should consider that the measurement "extends" also partly into the grain boundary as atoms get progressively disordered there (not abruptly!). As we have recently shown by analyzing pattern simulated from MD data, the size data comes out quite well.

I met with the fact that scientists often speak about "crystallite" and it really comes to them with a grain size of nano-

but in fact to measure crystallite size you can use Scherrer's formula however, this method is approximate

I keep insisting that there is NO universally accepted definition for the word "crystallite"...

1) Returned to the grain boundaries (GB), if the grain size is decreased, the GB thickness doesn't change, but if the crystal size of the grains is reduced the volume fraction of GB almost raises exponentially. For Example when grain size is reduced up to 5 nm (very small grains) the relative volume fraction of GB is around 50% therefore the effect of GB is huge in the material proprieties. this approximation can be derived from the following:

GB%=(grain total volume- grain boundary thickness volume) /grain size

I'll be back for the original question.....

I love the vociferous discourse. We are hung up on semantics and definition. It sounds great in writing. No one’s thought is drowned.

I want you to look at some of this data from a "single crystal" ZnSe wafer. You would not expect to see GB (sub-Grain Boundaries). It all depends on the resolution you are able to achieve both spatially (real space) and in reciprocal space (2Theta & Omega).

ZnSe (224) Asymmetric Reflection Bragg XRD micrograph:

http://www.flickr.com/photos/85210325@N04/8493232400/in/photostream

There are all kinds of GB's/GB running all over this supposed mono-crystal topographically.

YouTube Video: http://www.youtube.com/watch?v=dFCQS8oUyT0

As Matteo pointed out there is no agreed definition of crystallite or GB (grain boundary). Majid's point in general is correct in that the "boundaries" are at a higher state of entropy (strain).

Each one of you have excellent grasp of the subject of XRD.

Just curious how you named yourself "Deleted"?

SEM only gives you the same measure as most optical methods. SEM will not be able to ID the difference between large mono-crystalline particles versus the same size/shape poly-crystalline particle (grain). Again there is no agreed use of the words either. It depends if you are speaking to a nano-materials user or a micro-materials user, bulk or powder. I'm not the expert. However, I’d like to know a consensus so we can move forward and discuss the technical issues further.

Majid! "GB%=(grain total volume- grain boundary thickness volume) /grain size"

Don't forget as the particles (grains) get smaller the surface area increases dramatically (grain boundary).

First of all we need to define the following terms for convenience:

1. Thick vs. thin?

2. Order vs. disorder?

3. Particle vs. grain?

4. Grain boundary vs. sub-grain boundary?

5. Crystalline vs. what para-crystalline, semi-crystalline, amorphous?

The more I know makes me realize how much more there is to know!

Crystallite size and grain size are same but particle size is the part of grain or crystallite.....

Abhay, you better read the answers that have already been given. If you use diffraction then what people call "crystallite" is definitely NOT a grain. For sure for crystalline systems, what XRD "sees" is the smallest entity so any other size is larger (including the particle)! So you are completely wrong!

Let us see if there is concensus in this one aspect at the least Abhay.

Do you mean that "particle size" is "diffracting domain size" as in XRD?

the outcome of the Accuracy in Powder Diffraction conference (just finished) is clear: we are inaccurate on how we name things (and this is for sure the case of size obtained by xrd

Any volume of "powder materials" would have the following nano-structural morphologies present:

1. Mono-crystalline particles (separated from all others).

2. Poly-crystalline particles.

3. Agglomerates of multiple mono-crystalline particles.

4. Agglomerate of multiple polycrystalline particles.

5. Mixture.

Within each mono-crystalline particle you will invariably find smaller "diffracting domain sizes" based on the resolution available both in real space (spatial resolution) and in reciprocal space (2θ, ω).

This gets more complicated if we include amorphous or other semi-crystalline or para-crystalline phases.

Dear Matteo,

I respect your comments but will you please define the difference among grain, particle and crystallite?? Only in one statement............

Abhay! That is the point. In my opinion the definition depends on the resolution in practice.

To start with, let us just focus on two terms for now. "Grain Boundary" & "Sub-grain Boundary". When and where does one stop and the other begin?

I have not yet seen an unequivocal description of these terms. Would you like to take a shot Abhay?

Unfortunately on the site people look at the last 2 answers they see and then they propose their own answers.And of course people prefer the answers they understand versus the correct ones. This does not mean I give correct answers. I mean that some answers have already been given, some wrong ones have already been discussed and people keep reiterating. If you check the full discussion you find also this answer I gave 30 days ago. It can give you an idea why things are complicated:

grains can be crystalline or amorphous. Coherently scattering domains (I don't like to call them crystallites as there is no universally accepted definition for this term) are the crystalline regions of material that scatter coherently (and in general they show no coherence with the neighboring ones). They are single crystal in nature (but they are in a powder as defined in the diffraction sense). A grain can contain multiple domains (consider e.g. two domains highly misoriented each other). The grain and the domain size are seldom the same in a polycrystalline aggregate but can be the same in a proper nanosized powder

30 days ago

Matteo! "and in general they show no coherence with the neighboring ones"

Somewhere in here may be a key to this discussion. It may have to do, not with "black & white" but perhaps "shades of grey". Rather than a definitive "no coherence" may be "degree of coherence". Once again I'm certainly not an "expert" but would surely like to use a term universally agreed to mean the same. These days, with youngsters (my son) "bad" means "good". In old English "nice" meant "stupid". Out here in the US back in the 1990's (under Clinton) we even had trouble with the definition of "is" & "was". (I gratuitously threw that in there for levity)

Powder XRD (conventional diffractometery using 0D point counter) has such a wide range of application from SAXS, XRR, to WAXS including characterization of nano-structure of materials ranging from amorphous to crystalline (and "many shades of grey" in between).

I remain "open-minded" to suggestions from all participants.

In the Scherrer equation, the "particle size" or "crystallite size" or "grain size" would be the DIFFRACTING DOMAIN size. Initial element of Tarun Garg's question.

Any disagreements? (we could enhance it as we go along)

BTW I see IIT Madras & Bombay, where are the rest of you? Am I the only IIT Kgp. rep here? Get on board, let’s go! Let's hear from you. I realize there are virtually 10's of thousands enroled and graduating from the IIT system these days.

You may all respect my comments but I'd like to know if we agree or disagree with certain definitions and why. It is not personal. When we do this diligently & objectively, we will have the best "argument proof" definition that we could all agree with as technicians in order to be unequivocal.

Now let's discuss the other element of Tarun's question, SEM, TEM, DLS?

STEM - Cannot record crystallographic inhomogeneity. It is a high resolution micrograph with limited depth perception yet. EDX.

TEM - Great! Sample prep?

DLS - Awesome! http://www.micromeritics.com/pdf/MAS/posters/mas%20poster%20case%20study%20sizing%20nano.pdf

Super resolution!

Thickness limitations?

SAMPLE PREP?

Here again we will need to contend with the definition of "coherence" or "degree of" and the resolution available for such imaging. Presently, with XRD we are measuring the average in the sampling VOXEL, which usually contains no less than 10's of Billions of unit cells at least. This creates strong statistical precision/certitude to our measurements.

Our smallest sampling VOXEL thus far with Bragg XRD Microscopy has been 45x90x1.1µm^3 in the case of ZnSe mono-crystalline wafer.

To the main question what is the difference between, particle, grain and crystallite? Please see an explanation below:

Particle – is an entity which is comprised from a single or multiple grains. A powder is a collection of particles. The particle size may be determined by various methods; e.g. microscopy (SEM, TEM etc.), by their surface area using BET, by diffraction of light and more methods.

Grain - An entity which is part of a matter, typically solid, and is comprised of array of atoms arranged usually in three dimensional grid (lattice). Grains can be comprised of single or multiple domains with similar lattice arrangements (low angle boundaries, twins etc.). Grains are observed usually by microscopy (Optical, SEM, TEM, etc.). Their size can be determined either by microscopy (Optical, SEM, TEM, etc.) or by diffraction methods (XRD, EBSD, TEM, Neutron diffraction –ND, etc.). Diffraction methods (XRD, ND) are typically limited to grains smaller than 20-50 nm.

Crystallite – A small grain typically referred to grains in the nanometric size. Crystallites are observed usually by microscopy (HRSEM, HRTEM etc.), and their size can be determined either using diffraction methods XRD, ND, TEM or EBSD.

The term "particle size" or "grain size" is used when size of individual crystals is less than about 100 nm, becoze a particle of real crystalline powder sample consists of many fine units called "crystallites", which can be considered as a single crystal, as illustrated in attached figure. ...

Simple question in clarification:

At what angle (miss-match, tilt, twist) should we deem a low angle boundary as "sub-grain" as opposed to the alternative?

See example of fracture edge ZnSe (224) Bragg XRD Micrographs:

http://www.flickr.com/photos/85210325@N04/8686319956/in/photostream

"The term "particle size" or "grain size" is used when size of individual crystals is less than about 100 nm" - I'm not aware of any such concession for exclusive use yet. In fact, I expect significant difference of opinion on that claim.

One fact is clear, when I use any of these terms in my context I'll be sure to clarify my definition in the particular paradigm. There seems to be a lot of relativity to the use of these terms. In XRD it is essential to clarify the use of these terms as the measured parameters are average measures of correlation in the diffracting domains based on the resolution available.

Abdullah, unfortunately (and you're probably not enough into the field to understand this) this is not a simple question. And more ufortunately, many people do not care, as you simply suggest. This is a bad habit and it's definitely NOT a scientific approach.

The words don't have the same meaning and this is the main point of all the discussion!!

These days we need to be more careful as when my son (18) says "Dad I'm Bad!" he really means "I'm Good!" I kind of agree with Abdullah regarding staying "simple". But Abdullah, it would behoove us as scientists to be unequivocal about our definitions. That is the attempt here and not gratuitous pontification.

A perfect example is the definition of the word "blasphemy". Is it blasphemy to claim my faith and the righteousness of my chosen path to "Nirvana"? Anyone that doesn't agree with my vision of salvation may be in jeopardy of blasphemy. This issue of simple semantics is presently on trial in Egypt. Just a simple word! "Beheading" may the simple solution as in the past. But that won't stop others with conviction. Death, trial, tribulation doesn't scare faith! Didn't scare Galileo or Copernicus. Invisible line between blasphemy and free-speech! Neither a Kefir's rant nor a tyrant's taunt should deter the pious & faithful.

Sorry for the distraction (gratuitous pontification) but it is exciting that such topics are being debated publicly in Egypt now. It is only a first step in "Freedom". I see there are still a lot of "Earth is flat" crowd over there. But there is enough "free spirit" in Egypt that they will come to the right conclusion. The Genie is "out of the bottle". No going back! The "key stone" of democracy is "majority rules" but the foundation is "guaranteed rights (safe-guard) for the minority". The Indians legislated this 1947-1950 to protect the minority Muslim population. Even the law of the land for the rest of the Indians of "monogamy" is not enforced for the minority Muslims there (

My understanding of consensus so far in this discussion (I shall amend as we go along):

1. Crystallite size is used only in the contest of exclusively crystalline materials. This would refer principally to mono-crystalline (?) domains in potentially poly-crystalline agglomerates as constituents. In other words it would be the “diffracting domain size” for XRD. This is tricky for it depends on the resolution available. Sub-grain structure also falls in to this general category.

2. Grain size is used for materials irrespective of their degree of crystallinity (martensitic). Grain size may be used for materials both in bulk and powder form. Generally characterized by crystallographic discontinuities (grain boundaries).

3. Particle size is used predominantly for powder morphology. Individual particle may be agglomerates. Suspensions, solutions are included. Usually optical measurements including SEM, AFM.

4. Use "diffractogram" instead of "spectrum".

5. Use "Scherrer formula" not "Debye-Scherrer Formula". Let's attribute credit appropriately.

Notably, XRD & Scattering techniques provide the flexibility for measuring correlation distances/lengths ranging from 100's of nm to fractions of nm. With the X-ray rocking curve method one has the luxury of resolving nano-lattice strains in the fm.

These terms are sometimes used interchangeably and would need to be clarified often. It would be related to the forces in play between the “grains”, “particles”, etc.

Abdulla, please be more careful when you respond. respect yourdelf. Please read carefully what Dr. Matteo Leoni wrote to you. And if you think the question is simple please refer to my response a month ago. Good luck in your career.

No hard feelings. Each of us is entitled to his/her opinion and will learn as did all of us. In any case, I like the fact that I can amend my text at will. This allows me to learn and change my once held opinions. We must appreciate each other for having the courage to post. I hope more members would contribute. Thanks for participating, all! I continue to learn and grow!

Certainly post such questions and others like it on the following LinkedIn Group posts when possible:

1. X-ray Diffraction Imaging for Materials Microstructural QC:

http://www.linkedin.com/groupAnswers?viewQuestionAndAnswers=&discussionID=189258615&gid=2683600&commentID=140532636&goback=%2Eanp_2683600_1369907189536_1%2Eamf_2683600_12045948%2Egmr_2683600&trk=NUS_DISC_Q-subject#commentID_140532636

2. X-Ray Diffraction and Scattering Techniques

http://www.linkedin.com/groupItem?view=&gid=3614857&type=member&item=241973911&qid=ae9fa84f-1f22-47b8-9f9b-c529426e3119&trk=group_most_recent_rich-0-b-ttl&goback=%2Egde_3614857_member_244782133%2Egmr_3614857

[email protected]

The conclusions I have derived from above fruitful discussion are:

Particle size term is used in context of powders only.

If talk about compacted solids, grain and crystallite are same thing.

A grain is single crystal region separated from other grains by grain boundaries.

From Scherrer' formula we calculate crystallite size for powders as well as compacted solids.

From SEM,TEM and DLS we calculate the particle size for powders and for compacted solids SEM gives grain or crystallite size.

Please correct if i have misunderstood something.

Dear Tarun Grag, TEM can also give grain size, even in the nanometer range.

Ori! With TEM "sample preparation" would be the major challenge. You end up destroying the very sample you want to study. Especially nano-powders! I haven't directly worked with this aspect but can imagine the genius needed for the "sample preparation" involved in such materials.

Dear Ravi,

To use TEM for nc material, you need to suspend your powder in liquid, e.g. ethanol, then drop few drops on a grid that is pre-coated by say carbon. Let the liquid dry, coat with conductive coating, Pt, Au C etc and here you go. No damage to the powder. Good luck.

"No damage to the powder", you'd be able to confirm that postulation only when you were to compare the images of the powder before "suspend your powder in liquid, e.g. ethanol, then drop few drops on a grid that is pre-coated by say carbon. Let the liquid dry, coat with conductive coating, Pt, Au C etc". Oh! Don't forget electrochemically or otherwise etch the "hole" in the 2-3mm disc as well. Then look at a tiny "tear drop".

BTW what if the nano-powder were in a sintered composite?

Dear Ravi, I used this procedure successfully for both metallic and ceramic nc powders.

No damage is done to the powders. In addition many articles exist in the literature that use TEM on nc powders. Google it. Good luck.

Ori! I understand your expertise and experience with these materials. But TEM is not known anywhere in the literature as a non-destructive technique. So in order to claim "No damage is done to the powders" you'd have to image the sample before any sample preparation is undertake. This is an impossibility with the specimen preparation that is required to mount a

Dear Ravi,

Take a look in one of our articles regarding nc metals:

Journal of Alloys and Compounds Volume 509, Supplement 2, September 2011, Pages S794-S796

For ceramics we measured the grain size using XRD and confirmed it using HRSEM see : Journal of the European Ceramic Society 33 (2013) 1947–1954,

in addition we used TEM which we have not published yet where we confirmed that the particles were mainly single crystals, i.e. grains.

I'll send you a copy of few TEM photographs in your mail.

Ori! Awesome stuff! Thanks for sharing. Please send PDF files of the publications to my email if possible. I'll even post it through "Drop Box" for other participants, if so desired. Toda Chaver!

[email protected]

.. it seems we starting once more to run back in circles and forget all what has been said...

Ori, with XRD line profile analysis you measure DOMAIN size.

In your article (at least the one with Giora that I know) you use the Rietveld method to measure that value i.e. the Williamson-Hall approach that does NOT give the first moment of the size distribution, but just the ration between the 4th and the 3rd moment i.e. some volume averaged size.. If you find the same value out of Rietveld and out of TEM then you have an error cause from TEM you usually find the first moment of the distribution. i.e. the mean. The fact that they should not agree is easy to demonstrate.

If you have a look at my publications, already at the beginning of 2000 we have shown that can extract the domain size distribution and it agrees with TEM provided the grains, particles and domains are the same thing... and I mean the whole distribution nad not just some sort of average

Dear Matteo, Indeed we use the modified WH method on both XRD and synchrotron diffractions. Please specify an article that best explains the point you mentioned above and I'll read it. Thanks for the elaboration.

Dear Tarun, I had this confusion from long time, but fortunately , I think, I understand it. We did a course work project , To construct 3d video from 2d images of micro structure of alloy surface. Here micro structure means the stricture appear when you polish a alloy surface and observe under microscope. As I am attaching a video of our project http://i4.ytimg.com/vi/Olxf1MxSUoU/mqdefault.jpg, here you will see some black line through the structure which are the grain boundaries, and the volume under these boundaries are the grain size , the whole structure is the particle (say) and the crystallite size is the size of a monocrystaline particle with no grain boundaries.. I am not an expart, but I think, it will at least clear about grain size and particle size.. Cheers Dude...

Tarun,

What XRD actually gives us is the coherent domain size. This includes grains, sub grains, twins and other extended defects like stacking fault and anti-phase boundaries. There will be good agreement between grain size/crystallite size from XRD and TEM only when sample doesn't contain sub grains , twins and extended defects. And most of the time crystallite size and grain size can be used interchangeably.

But Particle can be of single crystal/grain or poly-crystals.

Don't forget "particle size" is also used for amorphous powders & polycrystalline agglomerates and thus may be independent of the crystallinity of the "particle". "Grain size" is used in a similar context as well. So, I would think it would require clarification when used.

The long & short of it, "What XRD actually gives us is the coherent domain size" & "with XRD line profile analysis you measure DOMAIN size". We are measuring this parameter in the reciprocal space. It has a 3D nature to it and may require more than one (hkl) measurement to fully characterize. RSM (reciprocal space mapping) is an example of the method used to define the 3D morphology of the "diffracting domain" size/shape

Domain size = Coherent domain size = Coherently diffracting domain size

This ranges from FEMTOMETRES (using rocking curve) or fractions of NANOMETER (using WAXS) or in the 100's of NANOMETERS (using SAXS). Of course, these and larger dimensions can always be determined using real time 2D XRD Microscopy. With 2D XRD Microscopy, measurements are made both in the "real space" and in the "reciprocal space" simultaneously. Just as in a TEM but lower spatial resolution, real time, in situ, higher depth capabilities, larger sample capabilities, no vacuum chamber needed, NDE, operator training is a lot easier, fully automated!

The measurement of "particle/grain" size by SEM & other optical methods will not be the same as with XRD in general. There is no other method (that I know of) to measure the diffracting domain size precisely other than XRD.

Dear colleague Garg,

Crystallite Size is Different than Particle Size. A particle may be made up of several different crystallites or just one crystallite so in this case (particle size = crystallite size)

Crystallite size often matches grain size, but there are exceptions

Crystallites are coherent diffraction domains in X-ray diffraction.

Particles are chunks/pieces (usually very small, below 1 mm) of solid matter, ensembles of atoms. Particles can be as small as two atoms (the nitrogen particle for example, N2)

Grains are volumes, inside crystalline materials, with a specific orientation.

Particles can be polycrystalline, single crystal or amorphous. A 100 nanometer particle of gold, for instance, can be made of:

a single gold crystal,

many grains with a grain size

Some cute "tail chasing" because of definitions of terms. The following terms seem to be used for crystalline materials, amorphous and composite materials interchangeably.

Throw in liquid crystals, single crystals, slips, twins, stacking faults, etc. and we have the present day paradigm. It would be rational for us in the "know" to unequivocally define these terms and avoid the iterative misconceptions :-) 

There are several other RG discussions regarding these disagreements as well.

Using techniques to measure reciprocal space parameters such as in XRD  or TEM allows measurements in crystal space (real space) down to fractions of femtometers and better. The difference would be sample preparation and magnification achievable. There is a whole lot more to compute than just the "domain size" with diffraction methods. The "line profile" includes a plethora of other Nanostructural parameters that may be detected through computations. These are powerful techniques and the knowledge has been tried and tested for over a century. I continue to learn!

X-ray Diffraction In Crystals, Imperfect Crystals and Amorphous Bodies by Andre Guinier. 1962

http://www.ebay.com/sch/i.html?_from=R40&_trksid=p2050601.m570.l1313.TR0.TRC0.H0.TRS0&_nkw=X-ray+Diffraction+In+Crystals%2C+Imperfect+Crystals+and+Amorphous+Bodies+by+Andre+Guinier.+1962&_sacat=0

https://www.linkedin.com/groups/2683600/2683600-6163698569082654720

https://www.flickr.com/photos/85210325@N04/10515372183/in/album-72157645018820696/

The crystalline size and particles are different. Particle size would be always the largest and may consist of several grains (crystals), and perhaps even grains of different materials. To view the materials should be in the order of ‘crystallite

Dear Tarun Garg ,

Hope this helps you.

It is important to be able to separate particle or grain size, crystal size, crystallite size and domain size. A particle, or grain, may consist of one or more crystals which are fused together which XRD can not measure. The crystal size is also not accessible to XRD except it is a single crystal. In the general case, a crystal may consist of several crystallites, which are fused by small angle boundaries. A crysallie is made up of wo or more domain sizes. Domain sizes is what is accessible to XRD hence it gives us the coherent domain sizes. Like Osman showed above, the crystallite and domain structure and the defect separating domains within a crystallite can only be directly investigated with HRTEM.

>>>Grain size usually refers to the average diameter of the individual crystal orientations found in poly-crystalline materials.

>>>Particle size refers to (again generally) the average diameter of a discrete piece of material, rather than a region in a material with a distinct crystal orientation.

>>> Crystallite size are coherent diffraction domains in X-ray diffraction.

Question related to crystal size calculations, if the crystal size is about couple of micrometers, which method I can use to do the calculation? Sherre looks like only suitable with less than one micro?

I did SEM measurement on this particular particle, it is 3 to 5 micro. Could This mean it is a particle not single crystal under SEM? I did Sherre calculation of this particle, and crysta size in 0.17 micro..I am kind of lost. could this mean

1 size under SEM is not single crystal's

2. Sherre method cannot be applied in this particle

Which methods can be used if I want to calculate larger size of single crystal, such as micro units? Which XRD software can be use?

Thanks a lot

If the instrumental peak width of your diffraction pattern is the major component of the total width then the application of the Scherrer formula (already poor for the determination of coherent domain size (crystallite size) unless you have monodisperse spherical crystals) is even less useful and the result is meaningless. As a rule of thumb, for conventinal diffractometers it is impossible to get a meanningful size for crystallites above 50 nm. Maybe 80 or 100 nm if you have an incident beam monochromator working only with CuKalpha1. In a synchrotron diffractometer specialized for very narrow peaks maybe you can get some significant results for 200 or 250 nm crystallites... If your particles are micrometric and your diffraction peaks peaks are so narrow that Scherrer gives more than 50 nm (0.05 micrometers) then crystallites are too big and Sherrer is not working (assuming you are using a conventional diffractometer). If you need to know if your 3-5 nm particles are single crystals you should probably go to the TEM and get a diffraction pattern over the whole particle.

I hope this helps.

The simple answer can be as follow:

Particle (agglomeration of some grains) => Grain (ensemble of some crystallites and sometimes consists of a single crystalline material) => Crystallite (is the smallest and can be mono- or poly-crystalline)

One can consider crystallite and grain size to be approximately the same. It is important to note that a grain consists of a single material, but maybe crystalline, or polycrystalline. 

For a complete characterization, you may need to use a TEM with additional analytical tools. But you can distinguish single-crystal grains from polycrystalline grains by switch the mode to diffraction: a single crystal grain will form a sharp diffraction pattern associated with that material, the transform of the crystal structure, while the polycrystalline grains will have multiple copies of the pattern, perhaps even rings. When you get to the particle size, it is always the largest, and may consist of several grains, and perhaps even grains of different materials. You will spend some time with your local microscopists in order to complete the characterization. 

The average crystallite size can be determined using the Scherrer equation, the grain morphology is commonly determined by SEM, and the particle size can be estimated from TEM image.

Also please note that Sherrer's formula is an approximation, and works best for nearly spherical particles. You will obtain the best results from TEM or AFM, especially for very small, or irregular shapes.