Material Science Practice Test: Imperfections in Solids — Flashcards

Imperfections in Solids topics include: Crystallographic defects classification, point and linear defects, interfacial defects and microscopic examination.

Solids can have several types of imperfections, including:
Point defects: These include vacancies, interstitials, and substitutional defects. Point defects can cause problems like decreased strength, decreased thermal and electrical conductivity, and increased susceptibility to corrosion.
Line defects: These include dislocations. Dislocations are line imperfections in a crystal, where the atoms around the dislocation are displaced from their lattice sites. The resulting distortion creates stress and strain fields around the dislocation line.
Surface imperfections: These include grain boundaries.
Volume defects: These include voids, inclusions, and precipitation regions. 

Here are some types of point defects:
Stoichiometric defects: These defects do not change the stoichiometry of the solid. One type of stoichiometric defect is the Schottky defect, which is a vacancy defect where the number of missing cations and anions in the crystal are equal.
Frenkel defect: Also called a dislocation defect, this is a type of point defect in crystalline solids. It occurs when an atom or smaller ion leaves its place in the lattice, creating a vacancy.
Impurity defect: This is when foreign atoms compress into the interstices or replace some atoms that make up the solid.
Substitutional impurity: In covalently bonded materials, substitutional impurities can create a unique imperfection in the electronic structure.