Dear colleague! It is surprising that XRD does not work. I would expect that a polycrystalline sample should give reflexes at different angle positions because the Bragg relation should match according to the turn of the grains. I guess another method which might work is SAXS. If the grain size is much larger than the X-ray wavelength the law of refraction has to be use and diffraction does not work. Refraction results in a broadening of the main reflex, too. The width is a measure for the average grain size. However, if the sample is mainly single crystalline with only some single grains ... this could be a job for XRT. I do not know the type, size and composition of your crystal. However, LST and Raman (tomography) could also be helpful. Good luck, M. Herms.

Dear Rajshree,

for elemental / chemical compositon EDX and XRF are used.

EDX option is part of a SEM, which might be available at your institution.

Good luck

"I have one transparent crystal" - What material do you think it is? What makes you assume it is crystalline?

"How can I know weather it is single crystal or poly crystalline?" By exposing it to a X-ray beam larger than the sample in transmission mode and capturing the image on the other side with a dental film or 2D detector. You'll recognize it instantaneously, real time. See examples of HgMnTe (reflection) and NaCl (transmission) in attached real time images.

"XRD can give answer but by looking can we say weather it is single crystal or polycryatalline?" Visually identifying crystallinity or amorphous content is not a reliable method. These methods would be impaired by how transparent, translucent or opaque your specimen would be and independent of how advanced the optical microscope used. The results would also depend on how anisotropic the material is optically.

How can I find contents and chemical composition of the crystal? Energy dispersive analysis

Assuming you were looking for a NDE tool!

Thank you all, Yes i will try and let you know if it works

Dear Prof. Garadkar,

Thanks for suggession.

R B Jotania

Dear Rajshree,

when working with a crystal phase, the first control to do is the optical (visible) microscopy. A slice (30 microns thick) can be examined under a polarizing microscope ( for mineralogy and petrography). If the crystal is a "single crystal" one will obtain only one interference figure; on the contrary, if it is a "polycrystal" many interference figures are obtained. The cost is very low, the results are unambiguous.

For chemical composition, EDX -SEM measurements are necessary (without destroying the sample).

All the best !

Dino

Respected Dino,

Thanks for critical answer and wishes too.

Regards

Rajshree

Using polarising microscope one can find out ...

Thanks, can anybody know where is Polarizing Microscope in India?

Dear Rajshree,

any Department of Mineralogy and Petrology ( in Universities or Research Centres) cannot work without a " polarizing microscope". Then I suppose that you can find it in the most important Universities in India.

All the best !

Dino

Instrumental Facilities available at the Department -

• X-ray Diffractometer XRD-7 -SEIFERT
• Polarizing Microscope -Leica

You have both available at your Chemistry Dept. Prove to yourself which one of these has your solution. BTW you need to find a local dentist for some "dental film" to use the diffractometer as I suggested. No sample prep required. In situ :-)

For a crystal grower, "maybe" poly or mono will not suffice. Certitude is required.

Post your results!

http://www.gujaratuniversity.ac.in/web/data/dept/tech-dept/DChemistry.pdf

"when working with a crystal phase, the first control to do is the optical (visible) microscopy." Correct! This is the conventional approach.

"A slice (30 microns thick) can be examined under a polarizing microscope ( for mineralogy and petrography)." This is known as "sample prep" and could take several hours or more. It is bound to change the local defect Nano structure which may have to be etched to expose the in situ Nano structure. "Thin slices" are really exciting to work with using XRD in reflection and transmission modes.

"If the crystal is a "single crystal" one will obtain only one interference figure; on the contrary, if it is a "polycrystal" many interference figures are obtained." This depends on the optical properties of the specimen. But the concept of using XRD is analogous. The interaction of X-rays is highly dependent on the relative miss-orientation among poly-crystals.

This should be the first "go to" cool real time NDE tool in every "Department of Mineralogy and Petrology" if not already. Is it not? Why not? No one has informed them yet of this open secret? :-)

Thanks Ravi

Regards

R B Jotania

To justify a single crystal form. Lawe photography will be used for different points in one direction. the points to give the same reflection point configuration represent a single crystal

to identify the composition of elements forming the compound chemical analysis is needed

Although EDX is a method recommended for determining elemental composition, one has to take appropriate care to interpret the data in order to avoid errors is compound characterization.

In a recent paper it has been shown that EDX is an inappropriate method for characterization of new materials based on elemental composition data. For details pl. see Article Comments on the papers recently published by Kalaivani et al

@Omar M S and @ B R Srinivasan,

Thanks for your interest and reply too.

Regards

R B Jotania

I would like to add few comments based on my experience…

When you placed a single crystal (transparent) on cross polarizing microscope where the crystal is viewed by polarized transmitted light and a second rotatable polarized filter is kept above the crystal to get a dark and bright fields during rotation of the crystal.

When a crystal rotates the plane of polarization, it appears light against dark background. Therefore when a crystal is rotated on a microscope stage, a position will be reached where the crystal appears dark (i.e it extinguishes the light) and again it appears light on further rotation which occurs for every 90° rotation.

If you placed a multiple crystal on microscope stage, the individual parts of the crystal would normally extinguish at different angles…

The only exception is; all optically anisotropic crystals rotate the plane of polarization but optically isotropic crystals like cubic crystals where an index of refraction independent of direction do not extinguishes the light for every 90° rotation…

So, a crystallographer chooses a single crystal using a cross polarizing microscope before mounting it on the diffractometer.

Dear Raghavaiah Pallepogu,

Thanks for your comments

Regards

R B Jotania

Raghavaiah Pallepogu!

What about an opaque crystal?

Dear Ravi,

when working with an opaque crystal, a "reflection microscope" has to be used; it was a typical instrument for metallurgists. One can obtain the same information ( as in transmitted light), since the laws valid for reflected and transmitted light are the same, with only one exception: in reflected light the information is limited to a few surface layers of your sample, since the light beam has a limited penetration power in an opaque material.

Thank you for your kind attention

Dino

"when working with an opaque crystal, a "reflection microscope" has to be used; it was a typical instrument for metallurgists"

Unless one uses special etchants as a metallurgist, it is impossible to distinguish between mono and poly crystals using light microscopes. Am I missing something?

I join Dr. Rajshree, Analysis by a polarizing microscope can inform you if it is a moncrystal or a polycrystal