X-ray Diffraction: A tool to analyze crystal structure

Dr. Tripti Richhariya

Assistant Professor - Department of Physics Kalinga University, New Raipur

X-rays, the kind of electromagnetic radiation, just like the visible light, infrared radiation, microwave radiation, UV-radiation. This implies X-ray reflect all such properties shown by visible radiation like; reflection, refraction, diffraction, polarization etc. However, the basic problem arises with X-rays is that its wavelength is too small, therefore normal diffraction grating is not suitable for studying various phenomenon of X-ray radiation, because the grating element of normal diffraction grating is large compared to the wavelength of X-rays. Furthermore, to solve this problem, in 1912, Max Von Laue proposed a model that instead of normal diffraction grating single crystal may work as a diffraction grating for x-rays. As the interatomic distance of crystal is of the order of wavelength of X-ray. Later on, experimental support to this model is provided by Friedrich and knipping by passing the X-ray through single crystal of Zinc blend (ZnS). This study is useful to find the defects, imperfections exist in the crystal.

Now the question is that how the X-ray diffraction takes place through three-dimensional crystal structure. Actually, what happens, when the x-rays say primary radiations are made incident on to the crystal, the atomic electrons receive energy and start vibrating back and forth about their mean position. As we know that vibrating charge particles able to produce radiation, thus the vibrating electron also behaves like a source of secondary radiation and produce radiation in all possible direction. These secondary radiations will be considered as the X-rays are scattered from the atomic electron illustrated in Fig. 1

Fig. 1 Scattering of incident X-ray through atomic electron

However, all such scattered radiations in all possible direction are not of our interest to analyze the crystal structure. Now the question is that which radiations are under considerable or which are not considered. To overcome this question Bragg brothers W. H. Bragg & W. L. Bragg put forward a model. In this model they represent that the lattice is considered to be comprised of large number of parallel planes possesses different orientation and the incident X-rays are supposed to be reflected from such lattice planes. Therefore, under this model diffraction of X-rays are equivalent to the reflection of X-rays from atomic planes. After this model only such radiations are under consideration which satisfy Bragg’s condition. The representative plot of Bragg’s reflection is demonstrated in Fig. 2

Fig. 2 X-ray Diffraction

Techniques for measuring X-ray Diffraction

  1. Laue’s Method
  2. Rotating Crystal Method
  3. Powder Diffraction Method


  1. Not applicable to soft sample.
  2. Crystallographic structure determination.
  3. Determination of average Crystallite size analysis.

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