I have always a bump in the diffraction patterns.
The majority of peaks were indexed.
The preparation temperature exceeded decomposition temperature of reagents and the melting point were not reached but we were close to it.
The peaks are well defined.
The bump exists while using one diffractometer it is not noticed by another (don't know if the technician proceeded in background or not).
Can diffractomer adjustment contribute on this or are there just amorphous parts in the preparation?
It is common with a bump in the XRD pattern. This is in many cases due to instrumental factors an not amorphous material. Some broad peaks are amorphous material that can be estimated. You will beed then to figure out which broad bumps that are sample related and which that are i trument related. The most certain is to spike your sample with a known amount of a well crystalline phase and use mass balance to figure out the amorphous amount.
Are you using the original specimen holder supplied by the manufacturer of your equipment? Many people make customized holders so that they can lesser amount of specimens during measurements. While using such holders (made of acrylic glass or perspex), in many cases, you see a hump at low angles. I hope this is not the case with you.
You can see how the hump from the plastic holder looks like by running an empty plastic holder upside down. Then you can run a non-diffracting single crystall width the same holder to see if the plastic hump is there. Your lab probably also has sintered corundum sample for diffeactomter alignment. If that sample shows the same hump then the hump is not related to amorphous material in your sample.
If you are really interested in amorphous quantification, spike your sample and run Rietveld refinement.
Since you are running the same sample on two different diffractometers and getting two different background patterns at low angles it points to an instrumental effect in the first diffractometer and not any amorphous in your material.
As has been mentioned, plastic holders can produce this type of effect. Can you give any more information about the differences between the two diffractometers and sample holders?
The amorphous contribution usually it is centered at about 20 degrees. In your case due to the large displacement of the bump on the two diffractometers I think that this effect could be due to the experimental set-up. The sample holder , the slits could create in many cases these anomalous effects.
Yes, there can be many different contributions to the background in your diffraction pattern, including the sample, the substrate, and the instrument.
As you obtain different results with two different diffractometers, my suspicion is that the data with the "bump" are from an instrument with a position-sensitive detector. This background contribution is common with such detectors, and its presence will change depending on whether or not the instrument uses a so-called knife edge (designed to minimize these kinds of effects) and also on the acceptance angle of the position-sensitive detector.
The data in your second red pattern do also seem to show contributions from another source, either the sample substrate or an amorphous component(s) in your sample. Note that the position of the "hump" can vary considerably depending on the nature of the amorphous material (e.g., plastic vs. glass sample holder, different glass/amorphous compositions in your sample).
I suggest that you analyze a standard (perhaps an NIST XRD standard such as LaB6) to evaluate the different contributions to your patterns.
I also know the type of bulge as seen in the first red and the first blue diagram. On my powder diffractometer I usually observe a broad hump centered at ca. 10° 2theta, which is superimposed on the common negative slope at the beginning of a scan. As my powders are known to be 100% crystalline, it has to be an instrumental effect.
In my case I believe that the 10° bump results from the sample holder, which has its rim in the same plane than the sample. ( I just wonder that "my" bump looks more or less identical when using plastic- or steel sample holders... what else could contribute this way?).In my lab we have a corundum sample for alignment which has no elevated rim of the holder, and that's the only sample which produces no bump.
Try to measure such kind of sample and if the bump disappears, it's a contribution of your sample holder. Unfortunately I have no idea how to overcome this blemish; I'm okay with it for now, but maybe someone has an idea how to improve the setup.
Simon, do you use a position-sensitive detector? If so, I believe this feature is due to the interaction between the direct beam, your sample, and the detector, which measures diffracted and scattered radiation over a range of angles simultaneously. Many instruments use a knife edge to minimize this effect, but incorrect adjustment of the knife edge can cause unwanted effects at higher angles.
Have you tried to place a flat crystalline plate (e.g., a quartz or corundum plate) into the beam? Your sample holder should not block the beam at any angle; if so, it is too high.
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