A crystal is composed of periodically arranged in a 3D space. On the other hand amorphous materials do not possess that periodicity and atoms are randomly distributed in 3D space. The scattering of X-rays by atoms is the point to be considered in that case. When there is periodic arrangement of atoms the X-rays will be scattered only in certain directions when they hit the formed lattice planes ( formed by atoms). This will cause high intensity peaks ( the width of the peaks depends on other variables).

Amorphous phase: X-rays will be scattered in many directions leading to a large bump distributed in a wide range (2 Theta) instead of high intensity narrower peaks.

Dear Vadym Chernobrovchenko ,

Arun Jangir already explained the difference in XRD pattern for crystalline and amorphous material.

In your case of a polymer material you will mainly have an amorphous state, which has an XRD pattern characterized by one or two very broad humps.

The XRD pattern of your polymer exhibits one 'hump' around 40° (there may be also one around 20°).

The tiny little peaks, which superimpose your overall XRD pattern, are mainly*) due to the (statistical) noise of the x-ray photon counting process.

You should increase the measurement time (at least 10 times) to reduce the noise and see whether there are really some 'crystalline' peaks present in your pattern.

The evaluation and interpretation of 'amorphous' pattern is not as 'easy' as for the 'crystalline' ones: when evaluating such pattern, you will get radial distribution functions (pair distribution functions) of the scattering atoms, i.e. informations about the mean distances with respect to the scattering centers of the nearest (atom) neighbor(s).

For an introduction into this subject you may have a look for example at:

https://www-ssrl.slac.stanford.edu/conferences/workshops/scatter2006/talks/hufnagel.pdf

*) exceptions are: crystalline impurities and residuals of the sample support (crystalline sample substrate)

Best regards

G.M.

Dear Vadym Chernobrovchenko ,

the tiny little peaks in your pattern is the statistical noise of the count numbers delivered by the photon counting process.

The mean value n of the noise is n = sqrt(counts). You can decrease the relative noise nrel=n/counts by increasing the measurement time...

But with respect to the envisaged structural information there is no information in the noise...

For details of the data evaluation please see the Hufnagel presentation mentioned above.

I must admit, that this is a tough subject...

Other techniques might be helpful (Raman spectroscopy, FTIR ...)

Vadym Chernobrovchenko

I worked for thirty years at the Sumy State University. He contributed to its development from a branch of the Kharkov Polytechnic Institute to a classical university.

The amorphous halo in the diffraction pattern is determined by the lengthchain and interchain distances. The complex shape of this halo can be approximated by the superposition of two or more Gaussian curves with maxima, the superposition of which can be represented based on the analysis of the X-ray diffraction patterns of the crystals of this polymer.