Understanding XRD (X-ray diffraction) analysis
X-ray diffraction analysis (XRD) is a materials science technique employed to ascertain the crystallographic configuration of a material. The method employs irradiation of a material with X-rays and analyzing the intensity and scattering angles of the X-rays that emerge from the material.
The primary purpose of utilizing XRD analysis is to identify materials by examining their diffraction patterns. In addition to phase identification, XRD also offers insights into the degree of deviation from the ideal structure due to internal stresses and defects.
How does XRD work?
XRD is based on the interaction of X-rays, which are electromagnetic radiation waves, with the regular arrays of atoms in a crystal. When X-rays encounter atoms in the crystal, they are scattered by the electrons in the atoms. This phenomenon is known as elastic scattering, and the electrons are called scatterers. The regular arrangement of scatterers produces a regular array of spherical waves. In most directions, these waves cancel each other out through destructive interference, but they add constructively in a few specific directions as determined by Bragg’s law:
2dsinθ = nλ
Here, d is the spacing between diffracting planes, θ is the incident angle, n is an integer, and λ is the wavelength of the X-ray beam. These specific directions appear as reflections on the diffraction pattern. Therefore, X-ray diffraction patterns result from electromagnetic waves interacting with a regular array of scatterers.
X-rays are used to produce the diffraction pattern because their wavelength is often in the same order of magnitude as the spacing between the crystal planes (1-100 angstroms).
Benefits and Applications of XRD
XRD is a non-destructive technique used to:
Identify crystalline phases and orientation
Determine structural properties such as lattice parameters, strain, grain size, epitaxy, phase composition, and preferred orientation
Measure the thickness of thin films and multi-layers
Determine atomic arrangement.
Who uses XRD analysis?
X-ray diffraction (XRD) is a valuable tool for measurement and analysis in various industries, sectors and disciplines. XRD is fast, accurate and reliable, making it a popular technique for the unambiguous identification of unknown materials. Sample preparation is minimal, and with the right analytical software, data analysis can be quite straightforward, even for industrial processes.
One of the industries that heavily rely on XRD is the pharmaceutical industry. XRD is used to characterise and clearly define the composition of materials. It enables chemists and scientists to assess the crystal structures of pharmaceuticals and measure the actual percentages of multiple components in formulations. It is a key method for analysis at all stages of drug development.
In forensic science, the main use of XRD is in trace analysis to detect very small amounts of substances. XRD can detect loose powdered materials, hair, glass fragments, paint flakes, stains and other small substances.
The microelectronics industry also uses XRD to characterise single crystal substrates such as silicon and gallium arsenide for use in producing integrated circuits. XRD identifies any defects within a crystal, helping to improve the quality of the final product.
In glass production, XRD identifies tiny crystals that can cause faults in bulk glass manufacturing. It also enables manufacturers to measure crystalline coatings for use in texture.
Lastly, in geological applications, XRD is an integral mineral exploration tool that has revolutionised the geological sciences. XRD enables the rapid identification of minerals in rock or soil samples and determines the proportion of these minerals in each sample.
Overall, XRD is a versatile tool that plays a vital role in several industries, making it an essential technique for measurement and analysis in various applications.
Advantages of using XRD analysis
X-ray diffraction (XRD) offers several advantages, including its fast analysis time (usually under 20 minutes), high accuracy, and reliability in identifying unknown materials. Minimal sample preparation is required, which makes it a popular choice for both industrial process applications and materials research. Data analysis can be made easier with the right software and even automated for use in quality control applications, making it accessible to non-expert operators.