X-ray diffraction is a tool for the investigation of the structure of matter. X -rays are scattered by interaction with the electrons of the atoms in the material being investigated. The technique began when von Laue discovered that crystals diffract x-rays in 1912. Since then it has been applied to chemical analysis, stress and strain measurement, the study of phase equilibria, measurement of particle size, as well as crystal structure.
To describe a material uniquely, generally two pieces of information are required: what are the elements present and how are they arranged. The first question is usually answered by chemical analysis techniques and gives the ratio of the elements present in the material. This is a chemical formula often called the chemical stoichiometry. The chemical formula does not describe how the atoms are arranged in space or with respect to each other. For example, the material calcium carbonate has the formula CaCO3, but can naturally occur with two different atomic arrangements. These atomic arrangements are called crystal structures. The different structures for the same chemical formula are called polymorphs. Calcium carbonate’s two most common crystal structures are orthorhombic and trigonal-rhombohedral. The first material is the mineral aragonite and the second is calcite. X-ray diffraction can be used to tell different crystal structures apart.
Important background information to know in order to perform XRD and analysis includes:
An X-Ray Diffraction machine