measuring superlattices in multilayered epitaxial structures.determining dislocation density and quality of the film by rocking curve measurements.determining lattice mismatch between film and substrate and to inferring stress and strain.determine of modal amounts of minerals (quantitative analysis).determine crystal structures using Rietveld refinement.
With specialized techniques, XRD can be used to: identification of fine-grained minerals such as clays and mixed layer clays that are difficult to determine optically.characterization of crystalline materials.Determination of unknown solids is critical to studies in geology, environmental science, material science, engineering and biology. X-ray powder diffraction is most widely used for the identification of unknown crystalline materials (e.g. A detector records and processes this X-ray signal and converts the signal to a count rate which is then output to a device such as a printer or computer monitor. When the geometry of the incident X-rays impinging the sample satisfies the Bragg Equation, constructive interference occurs and a peak in intensity occurs. As the sample and detector are rotated, the intensity of the reflected X-rays is recorded. These X-rays are collimated and directed onto the sample. Copper is the most common target material for single-crystal diffraction, with CuK α radiation = 1.5418 Å. K α1and K α2 are sufficiently close in wavelength such that a weighted average of the two is used. Filtering, by foils or crystal monochrometers, is required to produce monochromatic X-rays needed for diffraction. The specific wavelengths are characteristic of the target material (Cu, Fe, Mo, Cr). K α1 has a slightly shorter wavelength and twice the intensity as K α2. These spectra consist of several components, the most common being K α and K β. When electrons have sufficient energy to dislodge inner shell electrons of the target material, characteristic X-ray spectra are produced. Details X-rays are generated in a cathode ray tube by heating a filament to produce electrons, accelerating the electrons toward a target by applying a voltage, and bombarding the target material with electrons. X-ray Powder Diffraction (XRD) Instrumentation - How Does It Work?īruker's X-ray Diffraction D8-Discover instrument. Powder and single crystal diffraction vary in instrumentation beyond this. A key component of all diffraction is the angle between the incident and diffracted rays. These X-rays are directed at the sample, and the diffracted rays are collected. Typically, this is achieved by comparison of d-spacings with standard reference patterns.Īll diffraction methods are based on generation of X-rays in an X-ray tube. Conversion of the diffraction peaks to d-spacings allows identification of the mineral because each mineral has a set of unique d-spacings. By scanning the sample through a range of 2 θangles, all possible diffraction directions of the lattice should be attained due to the random orientation of the powdered material. These diffracted X-rays are then detected, processed and counted. This law relates the wavelength of electromagnetic radiation to the diffraction angle and the lattice spacing in a crystalline sample. The interaction of the incident rays with the sample produces constructive interference (and a diffracted ray) when conditions satisfy Bragg's Law ( n λ=2 d sin θ). These X-rays are generated by a cathode ray tube, filtered to produce monochromatic radiation, collimated to concentrate, and directed toward the sample. X-ray diffraction is based on constructive interference of monochromatic X-rays and a crystalline sample. X-ray diffraction is now a common technique for the study of crystal structures and atomic spacing. Max von Laue, in 1912, discovered that crystalline substances act as three-dimensional diffraction gratings for X-ray wavelengths similar to the spacing of planes in a crystal lattice.
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