X-ray Diffraction (XRD)

- Jun 17, 2017 -

X-ray diffraction (XRD) is a popular analytical technique which has been used for the analysis

of both molecular and crystal structures [79,88], qualitative identification of various compounds [89],quantitative resolution of chemical species [90], measuring the degree of crystallinity [91], isomorphous substitutions [92], particle sizes [93], etc. When X-ray light reflects on any crystal, it leads to the formation of many diffraction patterns, and the patterns reflect the physico-chemical characteristics of the crystal structures. In a powder specimen, diffracted beams typically come from the sample and reflect its structural physico-chemical features. Thus, XRD can analyze the structural features of a wide range of materials, such as inorganic catalysts, superconductors, biomolecules, glasses, polymers, and so on [94]. Analysis of these materials largely depends on the formation of diffraction patterns.

Each material has a unique diffraction beam which can define and identify it by comparing the diffracted beams with the reference database in the Joint Committee on Powder Diffraction Standards (JCPDS) library. The diffracted patterns also explain whether the sample materials are pure or contain impurities. Therefore, XRD has long been used to define and identify both bulk and nanomaterials, forensic specimens, industrial, and geochemical sample materials [95104].

XRD is a primary technique for the identification of the crystalline nature at the atomic scale [10,14,88,105]. X-ray powder diffraction is a nondestructive technique with great potential for the characterization of both organic and inorganic crystalline materials [106]. This method has been used to measure phase identification, conduct quantitative analysis, and to determine structure imperfections in samples from various disciplines, such as geological, polymer, environmental, pharmaceutical, and forensic sciences. Recently, the applications have extended to the characterization of various nano-materials and their properties [106]. The working principle of X-ray diffraction is Braggs law [88,105]. Typically, XRD is based on the wide-angle elastic scattering of X-rays [10,14,88,107109].

Although XRD has several merits, it has limited disadvantages, including difficulty in growing the

crystals and the ability to get results pertaining only to single conformation/binding state [14,108,110]. Another drawback of XRD is the low intensity of diffracted X-rays compared to electron diffractions [110,111].

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