Fundamental Principles
This law, expressed as (n*lambda =2d*sin*theta*) relates the wavelength of X-rays to the interplanar spacing of a crystal lattice.
What is Bragg's Law?
The plot of scattered X-ray intensity versus the angle 2θ is known as this.
What is a diffractogram (or XRD pattern)?
In a standard powder diffractometer, this is the name for the device that rotates the sample and detector to measure different diffraction angles.
What is the goniometer?
The primary use of XRD in materials science is to identify the different crystalline compounds present in a sample, a process known as this.
What is phase identification (or qualitative analysis)?
A repeating unit in a crystal lattice that, when repeated in three dimensions, forms the entire crystal structure.
What is a unit cell?
The phenomenon that must occur for diffracted X-rays to produce a measurable peak, where scattered waves are in-phase.
What is constructive interferance?
On an XRD pattern, the position of the peaks is primarily used to determine this property of the crystal.
What is the lattice parameter (or unit cell size)?
The method that uses a fine, powdered sample to ensure that many different crystal orientations are available for diffraction.
What is powder X-ray diffraction (PXRD)?
Besides peak position, other aspects of the diffractogram can be used to determine the relative percentages of different crystalline phases in a mixture.
What is quantitative analysis?
The planes of atoms that cause X-ray diffraction are identified by these three integers.
What are Miller indicies?
This fundamental property of a crystalline material causes it to act like a 3D diffraction grating for X-rays.
What is its regularly spaced arrangement of atoms?
In powder diffraction, the sharpness or "breadth" of the peaks can be used to estimate this property of the material.
What is the average crystallite size?
Unlike PXRD, this method uses a single, well-ordered specimen to get more precise information about a crystal's atomic positions.
What is single-crystal X-ray diffraction (SCXRD)?
XRD can be used to study this phenomenon, where a material's lattice parameters change due to external factors like temperature or pressure.
What is stress and strain?
The process by which X-rays interact with the electron cloud of an atom, causing them to change direction.
What is electron scattering?
A sample must possess a certain degree of this property for standard XRD to produce sharp peaks, rather than broad bands.
What is crystallinity?
The relative intensity of different peaks is influenced by the type and arrangement of atoms in the crystal, and is described by this set of integers.
What are Miller indices?
A bent crystal of quartz or graphite can be used between the X-ray source and the sample to produce this type of X-ray beam.
What is a convergent beam?
This analysis technique uses XRD data, along with a structural model, to refine the crystal structure and atomic positions.
What is Rietveld refinement?
This term refers to a collection of unit cells that form a continuous, ordered structure.
What is a crystal lattice?
The reason X-rays are the ideal form of radiation for this technique is that their wavelength is comparable to this distance.
What is the atomic spacing (or interatomic distance)?
This type of material produces a broad, diffuse pattern in XRD, rather than the sharp peaks seen with crystalline materials.
What is an amorphous material?
This advanced source of X-rays can provide a much higher intensity and resolution than a standard lab source.
What is a synchrotron?
In thin film characterization, this specialized XRD technique is used to measure film thickness, roughness, and density.
What is glancing incidence X-ray reflectivity (GIXR)?
A special case of XRD that is used for very small angles to probe larger-scale structures, such as nanoparticles or polymers.
What is small-angle X-ray scattering (SAXS)?