Header Ads

X-ray diffraction can define and identify even unknown materials

XRD is often used to identify and characterise known as well as unknown organic and inorganic crystalline materials. Each material forms a unique diffraction peak which is also called the ‘fingerprint’ of the material. Usually the strongest three beam or peaklines are used to characterize each material.These beams are compared to the data available with the ICDD (International Centre for Diffraction Data) formerly JCPDS (Joint Committee for Powder Diffraction Standards). The indexed data includes cell parameters, the density as well as the chemistry of the material so identification becomes easier. X-ray diffraction patterns are so accurate that they can even point out if the materials are pure or if they contain any impurities. 

 
Modern XRD instrumentation in testing laboratories is usually pre-loaded with the standard pattern or they have a licence which gives them access to the ICDD data. It becomes easy with the automatic search and indexing to identify the material as the automatic search provides a possible combination of elements which can be used to index the pattern.  The original reason for undertaking to do XRD was to identify the structure of the unknown material. Of course when the material is composed of single crystals the identification process is easier but even for polycrystalline materials powder diffraction is used as it provides information on the shape and size of a unit cell and the way atoms are arranged in the cell. Also each of the chemical compounds or phase of the mixture of compounds has a different diffraction pattern so the pattern. The peaks are often classified as major, minor or trace which helps to identify the phases more accurately.

XRD can be used on a number of materials to identify them like materials that are crystal, amorphous or liquid and also monatomic gas. Fortunately the pattern produced through X-ray diffraction is not dependent on whether the material is a pure substance or is in a state of physical mixture. It is still possible to identify the crystal structure of the material as well as the percentage of the given material in a physical mixture. This means that qualitative as well as quantitative analysis of the material is possible. In other words through XRD it is possible to get information on the state of the material.

X-ray diffraction has become a choice for testing all kinds of materials correctly as the technique is powerful and accurate. Through XRD patterns it is possible to analyse phases and the lattice parameter which help to identify the unknown material. The change in diffraction pattern of each compound is sometimes so slight that only an experienced XRD technician can make out the difference.  It is also possible to study the texture and the strain of the material as XRD beam pattern can show if the material has no strain, uniform strain or un-uniform strain. It is possible to identify the texture of the material from the way the grains are distributed in the sample material.

No comments