Familiarity with XRD analysis and its applications

What is the X-ray diffraction method?

X-ray diffraction or XRD analysis is a device for measuring the distances of atomic planes or in other words, identifying the structure of materials, the result of which is determining the name of the mineral or minerals that make up the sample. The XRD X-ray diffraction spectrometer is widely used in identifying unknown crystalline solid samples. Among the things that can be determined in XRD are the detection of the crystal phase, the size and shape of the crystal grain, the composition of the crystal atoms and its structure, etc. The X-ray diffraction pattern is unique for each material.

Samples used in XRD

• Powder samples
• Solid samples with a completely flat surface

What is an XRD device?

X-ray diffraction (XRD) spectrometer is a popular analytical technique that has been used to analyze molecular and crystal structures. Qualitative identification of various compounds, quantitative resolution of chemical species, measurement of the degree of crystallinity, isomer substitution, fault accumulation, polymorphism, phase transition, particle size, etc. When X-ray light is reflected by any crystal, it results in the creation of many diffraction patterns, and the patterns reflect the physical and chemical properties of the crystal structures. In a powder sample, the scattered rays are typically obtained from the sample, which reflect its physical and chemical structural features.

Analysis of the structure of materials by X-rays

Therefore, the X-ray diffraction spectrometer technique XRD can analyze the structural features along with other uncertainties of a wide range of materials such as inorganic catalysts, superconductors, biomolecules, polymers, etc. Each material has its own unique diffraction pattern, which can be defined and identified by collecting the scattered rays with the reference database in JCPDS (Joint Powder Diffraction Standards Association). The scattering patterns also explain whether the sample material is pure or contains impurities. Therefore, XRD analysis has long been used to define, analyze and identify materials and nanomaterials, forensic samples, industry and geochemical samples.

Advantages of XRD Analysis and its Scope

X-ray diffraction spectrometer has numerous advantages such as non-destructive nature, high sensitivity, reliability, easy sample preparation, fast speed, low maintenance cost. In XRD analysis, easy interpretation of data is possible which can be used for qualitative and quantitative analysis in a wide range of applications. However, it has few disadvantages due to the use of harmful radiation, in addition, it requires a standard reference to match for inference and is an expensive instrument.

Measurement of the percentage purity of a sample using XRD analysis

In XRD analysis, since each material has its own unique diffraction patterns, therefore, it is possible to identify materials and compounds using a database of diffraction patterns. Considering the ratio and composition of impurities present, the percentage purity of a sample can be obtained using the diffraction pattern. The basic prerequisite is to differentiate a crystalline sample (Figure 1) from a semi-crystalline one such as a polymer, e.g., cotton, and an amorphous material, e.g., phenol formaldehyde complex resin (Figure 2). This is the main tool for describing the solid state.

Figure 1: Typical XRD analysis scatter showing a crystalline sample

Figure 2: Typical XRD analysis scatter showing semi-crystalline and amorphous sample

What samples are used for XRD analysis?

Generally, samples are in the form of fine powders and diffraction can be obtained from flat surfaces made as couplers to the holder. The sample for analysis can be from a wide range of materials including inorganic aggregates, organic compounds, polymers, metals, composites, pharmaceuticals, nanotechnology, etc. XRD analysis can also be used to study and discover the quasi-crystalline structure of colloidal materials and materials provided that the deposition length is in the correct proportion. XRD analysis is often used for asbestos, catalysts, ceramics, chemicals, clays and minerals, cement, composites, corrosion products, ash, environmental studies, semiconductors, textiles, plastics, nanomaterials, pharmaceuticals, metals, alloys, etc.

In what fields is XRD analysis used?

• Qualitative analysis
• Quantitative analysis
• Determination of the structure of crystalline materials
• Size of crystalline materials
• Investigation of chemical reactions and identification of reaction products
• Determination of particle size
• Thin films
• Crystallinity
• Phase diagram studies

• Phase boundaries
• Solid solutions
• Phase transitions

X-ray diffraction analysis

X-rays were discovered by Roentgen in 1895 and within a few years some of their properties were reported.

Properties of X-rays

• X-rays travel in straight lines and can be parallelized by slits.
• X-rays are not charged particles, so magnetic fields do not affect or bend X-rays.
• X-rays are produced by the collision of a bunch of accelerated electrons with a target made of an element with a high atomic weight.
• Programmable X-rays (emulsion) affect photography and this property is used to detect X-rays.
• Upon “exposure” to X-rays, the electric charge is dispersed.
• In many materials, fluorescence is excited by X-rays.

The fact that X-rays travel in a straight line and have high penetrating power is one of the properties that makes them useful. However, like electromagnetic radiation, X-rays may be scattered by a grating. The gratings must be very close together in space when X-rays are used. For scattering in crystals, a correct distance factor has been found, where atomic or ionic distances are on the order of a few angstroms. In this case, scattering can be expected.

The method commonly known as X-ray diffraction, XRD, is the Debye-Hall-Scherr powder diffraction method. In this method, the sample is made up of a large number of randomly oriented tiny crystals, which are considered to be a single crystal. When a powdered sample is exposed to an X-ray beam, a continuous cone of scattered X-rays is produced that will be reflected onto a circular film surrounding the sample.

*The laboratories of Abrizan Industrial Research Company, located in Fars Science and Technology Park, are capable of measuring various water parameters as well as XRD analysis with experienced staff and the use of advanced devices and equipment.