XRD: X-ray Diffraction
Definition:A chracterization method to determine the crystal structure and texture based on the diffraction of X-rays on crystallographic lattice planes.
Explanation:XRD can be used to determine the crystal structure and to analyze the texture of single- or poly-crystalline materials. The principle of this method is based on Bragg´s law that describes the condition for constructive interference of diffracted X-rays on successive crystal lattice planes. If monochromatic X-rays are irradiated on a polycrystalline material, the X-rays (with a certain wavelength λ) will be reflected on those lattice planes that fulfill Bragg´s law.

Determination of the crystal structure is performed in an X-ray diffractometer, where the sample and the detector can be moved relatively to each other to measure diffraction intensities with changing 2θ (Bragg angle). Since the lattice spacing d can be calculated using Bragg´s law, the {hkl}-indices and the crystal structure can be determined.

texture measurement is also carried out with an X-ray diffractometer. Crystal structure and {hkl}-indices are known from previous determination of the corresponding diffractogram. Then, the {hkl}-pole figures can be obtained from measurements with fixed 2θ. These {2hkl}-pole figures are the basis for the calculation of the orientation distribution functions (→ODF).
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(a) Diffractogram of fcc material. (b) {110} pole figure.
SFB-Link:XRD allows the experimental determination of elemental steel properties. On the one hand, the presence and volume fraction of different phases such as ε-martensite, austenite or ferrite can be determined by analysis of an X-ray diffraction pattern. On the other hand, preferred orientations of crystals and, thus the anisotropy of the material can be measured by analyzing pole figures.
References:V. Randle und O. Engler, Introduction to Texture Analysis, CRC Press, 2000