I synthesized iron sulfide nanoparticles using thiourea but when i increase the amount of thiourea, i observe no peak in XRD pattern corresponding to iron sulfide. Please help or you can attach related text.
Dear Maninder Singh,
refer following articles related to XRD pattern of iron sulfide which is useful for you,
http://www.sciencedirect.com/science/article/pii/S0883292715000128
http://www.sciencedirect.com/science/article/pii/S0040603114001518
http://www.sciencedirect.com/science/article/pii/S1385894714012893
But in the XRD pattern there are peaks? Did you identified them? They pertain to other phases containing iron and/or sulfur?
One thing you should make sure is that iron-sulfide was indeed produced. Have you got independent evidence for that? Either SEM or TEM imaging, and Energy dispersive X-ray Spectroscopy (EDXS) or WDS? How large do you expect the FeS to be? What volume fration? If the volume fraction produced is too small, you may not get any peaks, since they may be very weak, and may be abosorbed by the substrate (here I confess I do not have any idea what thiourea is, and what the morpohology of the reactants and products is like.)
But the point is that you have to be certain that FeS is produced in sufficient quantity as large enough crystals. If you have very small crystals approaching nanometer length scales, you will have broad or diffuse peaks.
@ Marcelal Bini,
I saw only one broad peak in the XRD pattern which is not from any iron sulfide phase.
Hi Maninder, since you saw only one broad peak, it is likely to be an amorphous phase. I sincerely dobut you have any FeS at all. You need to check in the SEM to look at the microstructure, and do some EDS on any particles formed, to ensure you have any FES.
I think it is the amorphous FeS, which is always considered as the very small mackinawite.
As Penpeng has indicated, nanoparticulate mackinawite is not a very good x-ray reflector. Small crystalline materials will usually tend to produce low, broad XRD peaks rather than tall, sharp signals. That is one of the features of XRD. If you are relying upon a computer to analyze your results, you might have better luck if you would analyze the results by hand. The computer may not be able to "see" a low, broad peak that might be obvious in a visual examination of the results.
Further, due to the structure of the mackinawite crystal, it only produces a small number of XRD peaks and the largest of these peaks appears at a low angle (around 18 degrees) when using Cu K-alpha as the x-ray source. This means that a low, broad "peak" can get lost in the energy that the detector picks up from the Cu K-alpha radiation at low angles.
Prof. Stephen N Smith 's answer is in considerable detail, and i want to give some supplement. You can use TEM to study your sample and you will find the nanoparticals only have one lattice fringe image, it means the FeS is not a perfect crystalline compounds. To my point of view, this type FeS can be considered as a faulty mackinawite which is in the process of nucleation.
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