Dear Md Sariful Sheikh ,

I'll share a sample XRD with the same pattern I got some time ago from a mining sample, an exploratory probe hole sample.

There are many reasons to have such unusual behavior, (i) significantly small particle size, (ii) a complex mixture of amorphous and crystalline phases, in your case may rise from stoichiometry loss and several amorphous phases in your sample (iii) sample displacement, (iv) optical misalignment (v) significant defective crystals, (vi) huge sample stacking faults in an inhomogeneity sample preparation among several others phenomenological effects.

In the sample XRD I'm sharing, the solution was to increase significantly the X-ray power and collimation using a policapilary. The sample was measured in parallel geometry. The Blue line is the raw sample in theta-theta equipment and the red line is the same untouched sample in a theta-theta equipment using a policapilar in parallel geometry setup with 60 rpm of sample spinning, with a collection time of 2 s, and increasing step size of 0.0100 2theta in both measurements.

As a natural sample, the occurrence is not so unusual as in synthetic ones, the complexity of the sample explains the patterns, considering that each of the above interferences may occur in all and each component at the same time.

I suggest checking the synthetic route and perhaps altering it to reach a better, less defective material, with fewer contributions of undesirable amorphous phases. In simple words, a less complex sample that you may model in a structural fitting routine.

Best regards,

WNM

Dear Md Sariful Sheikh,

It can be due to the instrument or error in the sample setup. I have also observed a similar type of background while using an old PANalytical XRD machine. It resolved automatically when I repeated the measurement. You can also check repeating it. However, you can still try to fit this data as the background is expected not to significantly affect the structural information/parameters.

Dear Md Sariful Sheikh

In [1] you can find the following helpful paragraph:

"At lower angles the sample intercepts only part of the beam resulting in reduced beam intensity per unit area of sample surface and increases the likelihood of background scatter from the sample holder. At higher 2 θ angles less area irradiated, which would have an effect of decreasing diffraction intensity. The depth of penetration of the beam becomes commensurably deeper with higher angles. This effectively increases background as well as a sample displacement effect. Theta compensating divergence slits on some diffractometers are designed to lessen high-angle intensity loss and displacement effects and low-angle background scattering. One must always recall however, that the standard form of reporting relative intensity is with fixed-slit conditions and that variable slit data must be appropriately corrected."

Best regards

[1]http://clay.uga.edu/courses/8550/XRD.html

Dear Md Sariful Sheikh ,

in addition to the answers of Wagner Da Nova Mussel , Rajan Biswas and Mohammed Hussein j. H. Al'Atia, I would like to state that your sample keeps a lot of iron, the fluoresence of which is easily excited by the Cu K- radiation, which you have used for the diffraction experiment.

So part of your background is due to Fe K-radiation fluorescence radiation, unless you have used a monochromator in front for the detector. The increasing behavior may be due to the reasons mentioned by the colleagues above.

The application of a Co or Cr based x-ray tube will avoid Fe fluorescence back ground.

Best regards

G.M.

Если юстировка качественная (что желательно поверить), то рост фонового рассеяния связан с ростом площади поверхности облучаемого материала, который содержит элементы с повышенным эффектом флуоресцентного излучения под действием используемого рентгеновского излучения (характеристическое излучение).

All wrong!

This XRD pattern must have been collected on Bruker D8 Advance's DBO geometry, in which Motorized Divergence Slit (Constant Illumination Length) was used. TOPAS can fit this raw data without any problem. See supplementary document of this paper: Weerathunga, H., Tang, C., Brock, A. J., Sarina, S., Wang, T., Liu, Q., Zhu, H.-Y., Du, A. & Waclawik, E. R. (2022). J. Colloid Interface Sci. 606, 588–599.

By the way, sample fluorescence is not likely to give high background in Bruker's X-ray Diffractometer, which uses energy dispersive PSD LynxEye XE(-T).

Dear All,

Thank you so much for adding your thoughts which are very helpful for my understanding. I checked all the possibilities you suggested. I have used Bruker D8 Discover for the measurement. I measured the XRD profile of a standard poly-crystalline sample to measure the background from the instrument, and checked some other materials which may show fluorescence under Cu-Kalfa radiation.

I found that even the standard poly-crystal Si sample also shows background and the background intensity slightly lower at the higher angle. It seems to me that background may be from various factors like scattering from the air, and response of the detector.

However, the increasing intensity effect at the higher angle is from the fluorescence effect. I observed the same effect from other Mn/Fe based samples using Cu-Kalfa radiation. But the similar sample shows flat background under Mo-X-ray source. My understanding is that any amorphous phase can not affect the XRD intensity at higher angle. The amorphous phases generally contributes at lower angles, because that’s where the most common bond lengths or nearest neighbor atomic distances for the heavy atoms are. However, natural samples have a larger distribution of elemental mass and bond lengths, so may behave in different way. Please add here if you have other thoughts. There is so many things to learn.

Wish you very happy, healthy and prosperous new year 2022.

Best wishes,

Sariful

If you are still in doubt, you can send me your LaFeO3.brml file.

Hi Sariful,

Of course, fitting is the best option, you can remove the background using the origin as well. If your sample is fluorescent or has any emission properties, this type of typical XRD pattern comes.

However, to understand the problem itself with the XRD instrument or not, if possible run the similar sample in its powder form with a minimum scan rate! If you are using k-type borosilicate glass then use a less thick glass substrate to avoid such a situation. Hope this will be helpful! Otherwise fitting is the only option.