röntgendiffraktiokuvauksessa

Röntgendiffraktion, or X-ray diffraction (XRD), is a family of techniques used to study the arrangement of atoms in crystalline materials. When X-rays interact with a crystal, the waves are scattered by electron clouds in the lattice, and constructive interference occurs at specific angles. This phenomenon is described by Bragg's law, nλ = 2d sin θ, where d is the spacing between crystal planes, θ is the angle of incidence, and λ is the X-ray wavelength.

The most common form is powder XRD, in which a powdered or polycrystalline sample provides many randomly oriented grains and yields a diffraction pattern that serves as a fingerprint of the material. Single-crystal XRD uses a well-ordered crystal to determine full three-dimensional atomic structures with high precision. Instrumentation ranges from benchtop diffractometers to synchrotron beamlines, and detectors may be scintillation counters or two-dimensional area detectors.

Data analysis in XRD includes phase identification by comparing patterns to reference databases, determination of lattice parameters, and assessment of crystallinity. Microstructural information such as crystallite size and lattice strain can be estimated using peak broadening, and quantitative structural models are often refined by methods such as Rietveld refinement.

Applications span materials science, chemistry, geology, mineralogy, and pharmaceuticals. XRD is used to identify phases, characterize polymorphs, measure residual stress, assess crystallinity, and analyze thin films and coatings. The technique requires careful sample preparation and safety considerations due to exposure to ionizing radiation, controlled by appropriate laboratory shielding and protocols.