X-rays present a unique ability to the analytical chemist to understand the structure of materials. X-rays simply do not get reflected by reflecting surfaces superficially but they have the ability to penetrate and get diffracted from internal atomic layers within crystals. This possibility arises as their wavelengths are in the range of atomic dimensions of crystals that constitute most of the materials under examination.
XRD analysis has not only contributed to our understanding of arrangement of atoms within crystalline materials but has contributed immensely to establish purity of materials and identification of different phases. Such studies yield valuable details on materials ranging from polymers, metallurgical samples, pharmaceuticals, electronic components, minerals and nano materials. The scope of applications is vast and in this article some of the application areas of XRD analysis are briefly discussed.
Single crystal and Powder XRD analysis are two common techniques used in XRD laboratories. Both the techniques have a distinct advantage that they are non-destructive and it is possible to handle small amount of samples that are generally available. Single crystal studies provide the geometrical arrangement of atoms in the crystal lattice including critical information on bond lengths and angles. However, such studies take 2 to 3 days for data collection and subsequent analysis. On the other hand powder XRD analysis can be concluded in about half an hour. In addition sample preparation is simple and the information made available can be used for both qualitative and quantitative purposes.
XRD analysis is a valuable tool for development of new drugs, characterization of active materials and excipients, testing at different stages of manufacture for effective quality control. Such information helps to improve quality of formulations, bio -availability and improvement of stability characteristics.
Powder XRD is a powerful technique for characterization and grading of minerals. Each mineral has a well defined crystal geometry and yields a unique x-ray diffraction pattern which helps in taking commercial decisions before undertaking mining operations.
Changes in environmental parameters such as temperature and humidity can lead to certain solid phase transitions which can be conveniently monitored using powder XRD. Such information provides useful clues on the stability of final finished products and can make contributions to evaluate their stability behaviour.
Studies on nano materials
The properties of materials depend largely on crystal size. This feature can provide useful information on nano particles which are the building blocks of pharmaceuticals, polymers and composites.
Micro Electronics is contributing significantly to advances in computer and electronic consumer products. Silicon and gallium arsenide are two popular materials used in integrated circuits production. XRD has been used in such applications to provide useful information on crystal structures and defects in manufacturing of microelectronic components
Powder XRD plays a significant role in criminal investigations. Samples collected from scene of crime such as broken glass, paint chips, hair and powders provide unique x-ray diffraction patterns which can help trace their origin and ultimately to lead to the prime suspects.
XRD alone or in combination with other techniques such as chromatography, FT-IR or DSC provides valuable confirmatory information on nature and characteristics of materials.