Glossary term
X-Ray Diffraction
A materials characterization method that uses X-ray scattering from crystal planes to identify crystalline structure and phases.
Definition
methodX-ray diffraction is a characterization method that identifies crystalline phases and lattice spacing from the angles and intensities of diffracted X-rays.
XRD relies on constructive interference between X-rays scattered by periodic atomic planes. Engineers use diffraction patterns to identify phases, estimate lattice parameters, track texture, measure residual stress, follow heat-treatment transformations, and assess crystalline quality in metals, ceramics, minerals, semiconductors, and coatings.
X-ray diffraction measures how a crystalline material scatters X-rays as a function of angle. Peaks appear when planes in the crystal lattice satisfy the Bragg condition:
where lambda is the X-ray wavelength, d is the spacing between lattice planes, theta is the Bragg angle, and n is the diffraction order. The positions and intensities of peaks form a fingerprint of crystal structure and phase composition.
Engineering use
XRD is used to identify phases in alloys, ceramics, minerals, catalysts, corrosion products, thin films, and semiconductor materials. It can detect transformations caused by annealing, quenching, aging, oxidation, hydration, sintering, or service exposure. With suitable methods, it can also estimate crystallite size, lattice strain, preferred orientation, residual stress, and degree of crystallinity.
The technique is most powerful for ordered crystalline material. Amorphous content, very small crystallites, rough surfaces, strong texture, fluorescence background, peak overlap, and multiphase mixtures can complicate interpretation. Sample preparation, instrument geometry, radiation source, detector response, and database choice all affect results.
Common mistakes
A common mistake is treating XRD as a direct elemental analysis method. It identifies crystalline phases and lattice structure; elemental composition usually requires a complementary technique such as X-ray fluorescence or chemical analysis. Another mistake is overinterpreting weak or overlapping peaks without uncertainty, reference patterns, or sample-preparation evidence. A strong XRD report states radiation source, scan range, step size, sample geometry, calibration, phase database, fitting assumptions, and detection limits.