Kikuchimønstre

Kikuchimønstre, or Kikuchi patterns, are sets of diffraction lines observed when high-energy electrons interact with a crystalline material. They were discovered by Seishi Kikuchi in 1928.

Formation: In a crystal, incident electrons undergo inelastic scattering, creating a cone of exit directions. A portion of these electrons is Bragg-diffracted by lattice planes. For each family of lattice planes (hkl) two symmetric bands appear on a detector, forming a characteristic network of curved Kikuchi lines. The pattern is a projection of the crystal’s geometry and reflects the orientation of the crystal with respect to the beam.

Observation: Kikuchi patterns are commonly recorded in transmission contexts (TEM) or in scanning electron microscope setups using backscattered electron detectors (EBSD). The bands are broad and curved, and their intersections identify zone axes and crystallographic relationships.

Information: By indexing the pattern—matching bands to known plane families—one can determine the crystal orientation, phase, and local lattice parameters. The pattern can also reveal strain and microstructure information when analyzed quantitatively.

Applications: Used in materials science, metallurgy, geology, and ceramics to map crystallographic texture, identify phases, and study microstructures. Electron backscatter diffraction and transmission electron diffraction are typical modalities.

Limitations: Require suitable crystal thickness and quality, good surface condition for EBSD, and careful interpretation in low-symmetry or polycrystalline samples. Complex scattering can complicate indexing.

History: The phenomenon was first described by Seishi Kikuchi in 1928, with widespread routine use expanding after the development of EBSD and advanced TEM diffraction techniques.