AOA
Respected Friends
Can anyone help me.
The XRD graph of NaCoO2 is attached with. I just want to know why the data starts with maximum counts.
Thanks
SAIF
Dear M.S. Awan
the issue you are dealing with is the continous background.
You may have got a large amount of amorphous material in your x-ray beam, either as amorphous NaCo02 (but I don't know whether NaCo02 can be amporhous at all) or as XRD signal arising from your substrate/sample support (or any stray light !!!, see below).
The shape of amorphous material is characterized in a more or less structured very broad peak and a countinously decreasing background, which is decribed by the elastic scatter behaviour of single atoms (see Thomas's answers above), although you do not have any free atoms in your sample.
But a critical closer looking onto your diffractogram reveals that
a) there is no real amorphous broad peak present (such broad peaks pop up in the lower 2theta range)
and
b) the curvature of your background is more convex than concave as in the case of the atomic form factor.
So I would assume that your background is due to experimental issues such as height misalingment and/or perhaps other things such as not properly matched slit widths and not well aligned x-ray beam path, so that stray light arising from the vicinity of your sample (or from the vicinity of the x-ray spot at the sample surface) is able to enter your detector.
So please check your diffraction set-up by testing with a reference sample of well known composition and well known diffraction pattern.
Good luck.
Dear M.S. Awan
the issue you are dealing with is the continous background.
You may have got a large amount of amorphous material in your x-ray beam, either as amorphous NaCo02 (but I don't know whether NaCo02 can be amporhous at all) or as XRD signal arising from your substrate/sample support (or any stray light !!!, see below).
The shape of amorphous material is characterized in a more or less structured very broad peak and a countinously decreasing background, which is decribed by the elastic scatter behaviour of single atoms (see Thomas's answers above), although you do not have any free atoms in your sample.
But a critical closer looking onto your diffractogram reveals that
a) there is no real amorphous broad peak present (such broad peaks pop up in the lower 2theta range)
and
b) the curvature of your background is more convex than concave as in the case of the atomic form factor.
So I would assume that your background is due to experimental issues such as height misalingment and/or perhaps other things such as not properly matched slit widths and not well aligned x-ray beam path, so that stray light arising from the vicinity of your sample (or from the vicinity of the x-ray spot at the sample surface) is able to enter your detector.
So please check your diffraction set-up by testing with a reference sample of well known composition and well known diffraction pattern.
Good luck.
I fully agree with Gerhard, the decreasing intensity with nominal Bragg angle is a typical feature if the height of the X-ray tube is not properly adjusted on the theta-circle of the diffractometer. What kind of diffractometer are you using (Bruker, Siemens, Philips, STOE, ...? And which geometry (I guess Bragg-Brentano parafocusing geometry? - if so, then the proper alignment is a crucial prerequisite!) M. Awan, try to measure offset scans, i.e. virtually correct this misalignment - I guess this will help, and increase the intensity of your Bragg-peaks as well. Good luck, Dirk
I had observed the same phenomenon in one of my samples. I changed the quantity of the (same) sample and the problem was fixed.
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