I prepared nanoparticles, and as XRD results and XPS characterization confirm, I have zerovalent iron, hematite and iron nitride nanoparticles.
However, when I prepare samples for TEM and SAED characterization, measured patterns, assuming that I obtain it with proper calculation, differ from the one in a database and I have only one or two (hkl) direction same as the one from database or XRD results. In reserchgate portal, a lot of researchers debate that there is NO difference between nanoparticles data and thin.fims, bulk XRD data, however, Qianghua LU et al in A Comparative Study on the Selected Area Electron Diffraction
Pattern of Fe Oxide/Au Core-shell Structured Nanoparticles reported, (J. Mater. Sci. Technol., Vol.23 No.2, 2007) a
comparative study on selected area electron diffraction
(SAED) patterns of the as-prepared composite
nanoparticles is presented. For the composite particles
with a mean size less than 10 nm in diameter, it
is interesting to find that their SAED pattern differs
from either the pattern of pure Fe oxide nanoparticles,
or that of pure Au particles. Is this observed difference and incapability to find more than two matches of patterns in database, sign that particles are polycrystalline, contaminated, different arrangement on nanolevel, or something else?
Hi
phase analysis for XRD must have precise matching between pattern and measured value, I used Xpert software so, it was very helpful tool
I Hope it help
If I'm understanding your issue correctly, then what you're saying is that when you run XRD on your material the results match the JCPDS files, but when you do SAED on the same material you're only getting one or two matching diffraction directions, is that correct? Powder XRD patterns are based on a large number of particles with random orientations so that you get all possible diffraction directions. In SAED you're dealing with a much smaller number of particles, so one possibility is that your SAED patterns simply do not have enough particles with the proper orientations to get all the diffraction directions.
yes you are correct Andrew,
but why I dont obtain exactly the same phase? if XRD show Fe2N... SAED will be Fe8N or Fe, similar with other metallic nanoparticles. Is that mean I cannot conclude undoubtedly what is my phase?
I don't much about the Fe-N system, so I'm not sure how close the diffraction peaks between the various phases are to one another. I can say from my experience with iron-oxides when two phases have similar diffraction peaks they can be difficult to resolve with XRD. I've also had situations where I synthesized magnetite nanoparticles, which I confirmed where magnetite using XRD. But when I did SAED on some of the particles I got peaks for other iron oxides (goethite). Turns out the goethite was present in the material, but at trace levels so the XRD missed it, however, in SAED it had a much higher relative abundance so I could resolve it in the SAED pattern. Maybe something similar is happening with your material.
Oh, I see, thank you,
what technique supplementary to XRD, and SAED can you suggest me to use in order to confirm all phases? RBS, XRF?
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