A beginner’s guide about X-ray diffraction
X-ray methods have been among the most powerful and versatile instruments in scientific research, medicine, and technology for over a century. The unique properties of X-ray radiation make it possible to carry out non-destructive diagnostics, introspection, to detect certain types of substances and to investigate their properties. It can be said that since the wavelength of X-rays is comparable to the characteristic distance of interatomic bonds, it allows us to look deep into matter.
Therefore, today X-ray studies are used in solving a wide range of tasks — in scientific and medical research, in developing methods of synthesis of new materials, in light and heavy industry, building capacity, security, non-destructive testing and many other areas.
One of the main and widely sought-after areas of X-ray research is X-ray crystallography analysis, which answers basic questions about the crystal structure of matter and its properties. X-ray diffractometry is an effective method of X-ray crystallography analysis.
Why were special research methods needed in this area? The whole thing lies in the wave nature of physical interactions (sometimes it is possible to talk about interaction through particles, as well as about the so-called wave-particle dualism, but this, as they say, is another story). The fact is that the main scale that can «feel» a wave is the scale of distances comparable to the length of that wave.
Resting on the warm shore of the lake or the sea, you can see that the wave can freely passing through a small rock or cane as they size is less than the wavelength. A different picture occurs if the wave meets a large rock, then a wave shadow is formed behind it, where the waves do not penetrate, as on Figure 1.
Resting on the warm shore of the lake or the sea, you can see that the wave can freely passing through a small rock or cane as they size is less than the wavelength. A different picture occurs if the wave meets a large rock, then a wave shadow is formed behind it, where the waves do not penetrate, as on Figure 1.
Waves thus pass through obstacles in different ways depending on their size relative to the wavelength: ignores small ones and bend behind larger ones. The phenomenon of wave deviation from linear propagation is called diffraction.
The characteristic dimensions of crystalline structures in solids are much smaller than the wavelengths of visible light rays, so it is impossible to see the crystal structure using it, just as the sea wave will not be affected by an obstacle as a small pebble or cane. Here, it is necessary to use more short-wave radiation and X-rays are just suitable for this.
Passing through the crystalline structures in matter, X-ray radiation changes the direction of propagation depending on the size of the crystalline structures (more precisely, the distance between the atomic planes), like waves bent behind a large stone in the water. By studying these changes in X-ray propagation, it is possible to reconstruct the studied crystal structure, which is the essence of X-ray diffractometry.
The study of the structure of the crystal lattice is important for a wide variety of fields of science and technology – technical, engineering, medical and anywhere knowledge of the properties of substances is required.
Now we are ready to dive into how X-ray diffraction works in practice.
X-rays fall on a crystal structure and, since the structure is periodic, we get to observe a number of interesting physical effects. The effects are due to the fact that the radiation begins to interfere at the centers of the crystal lattice and, passing through them, forms a completely unique diffraction pattern (the so-called diffractogram), characteristic only of a given type of crystal lattice (Fig. 2).
Thus, we illuminate crystals and crystal objects with appropriate wavelengths, obtaining at the output some image, which will identify the type of organization of atoms within a given crystal structure (Fig. 3).
Instruments that allow such measurements and record diffraction patterns or part of them are called X-Ray diffractometers. The LINEV GROUP has developed new effective X-Ray diffractometer, called “TELLUS” for crystalline powder analysis (Fig.4).
To read more about this device and in general about X-Ray diffraction projects in LINEV GROUP see continuation of this story. To be continued…
