Defects in solids

A solid material consists of some sort of defects. Various point defects observed in a solid are vacancy, Schottky, Frenkel, self-interstitial, interstitial impurity, colour centres, vacancy through aliovalent impurity, charge compensation and non-stochiometry. Edge dislocation and screw dislocations are the commonly observed one dimensional line defects. Commonly observed two-dimensional plane defects are grain boundary and stacking faults. If some of the lattice points normally occupied by metal ions are vacant, it will result in vacancy defects.This is observed in copper. Schottky defects are observed in ionic crystals. Frenkel defects are observed in silver halides which assume open structure symmetry. Self interstitial defects are observed in elemental solids. The introduction of impurity is causing interstial impurity defect. The introduction of aliovalent cation or anion into ionic solid produces vacancies. Charge compensation defect occur in ionic solids. Colour centers are defects which imparts colour to the colourless material. Grain boundaries are surface imperfections commonly observed in polycrystalline materials. Stacking faults are defects which occur due to dissociation of a dislocation. This type of defect is common in crystals which are grown in the laboratory.