Search Results for polycrystalline sample

X-ray powder diffraction (XRPD) techniques are used to characterize samples in the form of loose powders, aggregates of finely divided material or polycrystalline specimens. This article provides a detailed account of XRPD. It begins with a discussion on XRPD instrumentation and the techniques used to characterize samples. The article then describes the principles, advantages, and disadvantages of various types of powder diffractometers. A section on the Rietveld method of diffraction analysis is then presented. The article discusses various methods and procedures for qualifying and quantifying phase mixtures in powder samples. It provides information on typical sensitivity and experimental limits on precision of XRPD analysis and other systematic sources of errors that affect accuracy. Some of the factors pertinent to the estimation of crystallite size and defects are also presented. The article ends with a few application examples of XRPD.

This article introduces various techniques commonly used in the characterization of semiconductors, namely single-crystal, polycrystalline, amorphous, oxide, organic, and low-dimensional semiconductors and semiconductor devices. The discussion covers material classification, fabrication methods, sample preparation, bulk/elemental characterization methods, microstructural characterization methods, surface characterization methods, and electronic characterization methods.

Crystallographic texture measurement and analysis is an important tool for correlating material properties with microstructural features. This article describes the general approach to quantifying crystallographic texture, namely, the collection of statistical data from grain measurements and subsequent analysis based on Euler plots (i.e., pole figures), orientation distribution functions, and stereographic projections. Using detailed illustrations and examples, it explains the significance of preferred crystallographic orientations and their influence on properties and material behavior. The article also discusses sample selection and preparation as well as the challenges and limitations of various methods.

X-ray powder diffraction (XRPD) techniques are used to characterize samples in the form of loose powders or aggregates of finely divided material that readily diffract x-rays in specified patterns. This article provides an introduction to XRPD, beginning with a review of sensing devices, including pinhole/Laue cameras, Debye-Scherrer/Gandolfi cameras, Guinier cameras, glancing angle cameras, conventional diffractometers, thin film diffractometers, Guinier diffractometers, and micro diffractometers. The article then describes several quantitative measurement methods, such as lattice parameter, absorption diffraction, spiking, and direct comparison, explaining where each may be used. It also identifies potential sources of error in XRPD measurements.

Low-energy electron diffraction (LEED) is a technique for investigating the crystallography of surfaces and overlayers adsorbed on surfaces. This article describes the principles of diffraction from surfaces, and elucidates the method of sample preparation to achieve diffraction patterns. The article describes the limitations of surface sensitive electron diffraction and discusses the applications of LEED with examples.

X-ray topography is a technique that comprises topography and x-ray diffraction. This article provides a description of the kinematical theory and the dynamical theory of diffraction. It provides useful information on the configurations of reflection and transmission topography. The article explains various topographic methods, namely, divergent beam method, polycrystal rocking curve analysis, line broadening analysis, microbeam method, and polycrystal scattering topography, as well as their instrumentation. It also describes the applications of x-ray topography.

Low-energy electron diffraction (LEED) is a technique for investigating the crystallography of surfaces and overlayers adsorbed on surfaces. This article provides a brief account of LEED, covering the principles and measurements of diffraction from surfaces. Some of the processes involved in sample preparation are described. In addition, the article discusses the limitations of surface-sensitive electron diffraction and the applications of LEED with examples.

Pure metals normally solidify into polycrystalline masses, but it is relatively easy to produce single crystals by directional solidification from the melt. This article illustrates the dislocations present in a metal crystal, which is often polygonized into sub-boundaries during grain growth after solidification. It provides a description of small-angle and large-angle grain boundaries of polycrystalline metals.

This article describes the integration of thermodynamic modeling, mobility database, and phase-transformation crystallography into phase-field modeling and its combination with transformation texture modeling to predict phase equilibrium, phase transformation, microstructure evolution, and transformation texture development during heat treatment of multicomponent alpha/beta and beta titanium alloys. It includes quantitative description of Burgers orientation relationship and path, discussion of lattice correspondence between the alpha and beta phases, and determination of the total number of Burgers correspondence variants and orientation variants. The article also includes calculation of the transformation strain with contributions from defect structures developed at alpha/beta interfaces as a precipitates grow in size. In the CALculation of PHAse Diagram (CALPHAD) framework, the Gibbs free energies and atomic mobilities are established as functions of temperature, pressure, and composition and serve directly as key inputs of any microstructure modeling. The article presents examples of the integrated computation tool set in simulating microstructural evolution.

This article describes the methods of X-ray diffraction analysis, the types of information that can be obtained, and its interpretation. The discussion covers the basic theories of X-rays and various types of diffraction experiments, namely single-crystal methods for polychromatic and monochromatic beams, powder diffraction methods, and the Rietveld method.