Defektstellen

Defektstellen, or defect sites, are locations in a material where the ideal crystalline order is disrupted. They occur in metals, ceramics, semiconductors and polymers and influence a range of properties, including strength, conductivity, diffusion and chemical reactivity. Defektstellen can be classified by dimensionality and nature of the disturbance.

Types of defects include point defects (such as vacancies, self-interstitials, substitutional atoms and Frenkel pairs), line defects (dislocations) and planar defects (grain boundaries, stacking faults, phase boundaries). In polymers, defect sites may arise as chain ends, voids or irregular crosslinking. In semiconductors, impurities and antisites also contribute to defect chemistry and electronic behavior.

Formation and dynamics:

Defect sites form during synthesis, processing or irradiation, and can also arise from mechanical deformation. Their concentration and distribution depend on temperature, pressure and chemical environment. Many defects are mobile at elevated temperatures and can migrate, interact or annihilate, while others act as traps for impurities or charge carriers.

Effects and applications:

Defect sites affect mechanical performance through dislocation motion and hardening, alter diffusion pathways, and modify electrical and optical properties. They play a crucial role in corrosion, catalysis and semiconductor device operation, where defect concentration and type control carrier lifetimes and recombination, or diffusion-mediated processes.

Detection and analysis:

Characterization methods include microscopy (transmission and scanning electron microscopy), diffraction (X-ray diffraction), spectroscopy and advanced techniques like atom probe tomography and positron annihilation spectroscopy. Computational modeling complements experiments by predicting defect formation energies, migration barriers and interaction with impurities.

Relevance:

Understanding defect sites is essential for materials design and performance prediction across engineering, electronics, energy storage and catalysis.