X-Ray Powder Diffraction

X-Ray Powder Diffraction (XRD) is a nondestructive technique that obtains detailed information such as chemical composition of the material, the crystallographic structure or morphology of the atoms or molecules inside the material, as well as the physical properties of the material. Our technicians are trained experts at material characterization and specialize in using XRD techniques to perform analysis of powder, film, nano-materials and bulk materials.

Technique Description

X-Ray Powder Diffraction (a.k.a. XRPD, PXRD, XRD) is most widely used to study the phase and crystal structure of substances. Each chemical molecule or phase has a unique diffraction pattern when the material is analyzed by XRD.

For example, if the material is crystalline, it possesses a three-dimensional structure with repeat units (unit cells) arranged in atoms. X-rays are diffracted by the repeating lattice spacings of crystalline materials, whereas they are simply scattered by amorphous materials. X-ray diffraction occurs at specific angles (2θ) with respect to the lattice spacings defined by Bragg’s Law:

Fig. 1 Schematic diagram of Bragg’s Law. (From Wikipedia, the free encyclopedia)

In the formula, n is an integer denoting the reflection order, λ is the X-ray wavelength, d is the lattice spacing between crystal planes, and θ is the diffraction angle. Consequently, the composition, crystal form, intramolecular bonding way molecular configuration and conformation, etc. will determine the unique diffraction pattern of the material. The diffraction patterns can be checked against large libraries of patterns from known materials to identify/quantify the phases present in the sample.

The XRD analysis has the advantages of no damage to the sample, no pollution, quickness and high measurement accuracy, and it can offer a large amount of information about crystal integrity. Therefore, XRD analysis, as a modern scientific method of material structure and composition analysis, has gradually been widely used in the research of various disciplines, such as geology, environmental science, material science, engineering, and polymer science.

Technique Capabilities

• Chemistry (Materials)
  • When the substance is composed of multiple crystalline components, the XRD phase identification function can be used to analyze the proportion of each crystalline phase.
  • The development of new materials requires a full understanding of the lattice parameters of the material, and the lattice parameters can be quickly tested by XRD, providing performance verification indicators for the development and application of new materials.
  • Failure phenomena such as fracture and deformation of the product may involve the influence of microscopic stress. Lattice compression or expansion High Resolution XRD (HRXRD) can quickly determine this kind of stress.
  • Small Angle X-ray Scattering (SAXS) is suitable for determination of the average particle size, mesoporous structure and spacing of agglomerated nanoparticles.
• Biology (Drugs)
  • Multiphase phenomena are common in drugs. XRD is widely used in the identification of drug crystal forms, the identification of ingredients in compound drugs, drug prescription screening, and the monitoring of drug reaction kinetics during production and storage.
  • As regards to modern medicines, the applications of XRD analysis include: single compound identification; determination of the crystal form of a single compound; determination of the purity of raw materials; determination of the stability and influencing factors of the drug substance; quality control of pharmaceutical preparations.
  • Especially for traditional herbal medicines that are not a single chemical substance, XRD can be used to analyze the various phases and related ingredients contained in them.
  • XRD characterization can also distinguish the authenticity of traditional herbal medicines, and can analyze composition changes of medicinal materials from different origins, picking periods and different parts.
  • XRD can be applied to study the dynamic processes of the protein, like ligand-induced protein conformation changes in biological research.
• Other Fields (Minerals)
  • The mineral phase transition includes two types: the chemical composition is unchanged while the crystal structure is changed; or the composition and structure are both changed. Mineral phase transformation can be studied by powder crystal X-ray diffraction method.
  • The types and properties of clay minerals and non-clay minerals in sedimentary rocks have a great influence on the production of oil and gas fields. XRD analysis of these clay minerals can provide a basis for oil and gas exploration and development.
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