Dear All,
I have to analyze a Co based superally sample where are present two different crystal structures of Co (the cubic and the exagonal one).
I'm sure of it because I have analyzed the sample by EBSD.
Now on the samples analyzed at EBSD I'm trying to perform micro X ray diffraction with Empyrean Panalytical instrument using the microbeam incident optics but the pattern that I obtained is only background, without any peak.
In your opinion which is the problem? Is it possible to perform XRD diffraction on a sample polished?
Do you have some instrution about micro XRD? it's my first test with this kind of incident optics
Thank you everyone
Emma
Depends on what XRD you performed... Cause polishing of the surface can induce strains under it.
Is micro-diffracion is polychromatic (Laue) technic?
If you already make EBSD and you see your grains, I think you have take care about the area prospected by the beam.
X ray are more penetrating than electrons, so it could also be a problem of different deep comparison between both techniques.
Dear Emma,
the Co K-edge is at 7,7keV and exciting with Cu K-alpha ( ~8keV) will give you a lot of Co K-alpha fluorescence radiation (and Fe K-alpha, if Fe is present in your sample). Any diffraction peak will be burried in the noise of that fluorescent background.
You should go for a Co tube; so both Co fluorescence (and perhaps Fe fluorescence) will not show up and background is significantly reduced.
Polishing will not be the reason for having no peaks.
On the other hand you may suffer from preferred orientation when having no powder sample. But I cannot imagine that all peaks dissapear in this case because your sample is still polycrystalline.
Best regards
Co sample produce lot of noise when analysed with Cu Ka radiation, so as advised by Dr. Martens, you can change the target (Co will be good). Penetration of Cu Ka radiation in Co sample is very less (~10-12microns max), i.e it is very surface sensitive, so surface must be free from defects (normal polishing degrades the surface, electro polishing is advised, annealed unpolished sample will give best result). The area coverage of micro x-ray beam must be sufficient to cover number of grains, otherwise it will behave like single crystal (grain size of >100 microns can cause problems).
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