Mumbai university > FE > SEM 1 > Applied Physics 1

Marks: 5M

Year: Dec 2012

Real Crystals:-

• Unlike ideal crystals, real crystals have imperfections.

• Any deviation from the standard lattice pattern of a crystal is an imperfection.

• The imperfection may be because of presence of impurity atom or a disturbed crystal structure.

Point Defects:-

Point defects or a zero-dimensional defect are the defects that occur only at or around a single lattice point. Point defects include:-

• Vacancy – Removal or a missing atom from its regular position.

• Interstitial – Presence of an extra atom of same crystal in the void spaces of crystal lattice.

• Substitution Impurity – An atom from the crystal gets replaced by a foreign or impurity atom.

• Interstitial Impurity – A foreign or impurity atom occupies a void space in crystal lattice.

• Shottky Defect – A missing pair of anion and cation from the crystal structure.

• Frankel Defect – A cation or an anion gets displaced from its original position in the lattice and occupies a void space. It generally occurs due to displacement of cations as they are generally smaller in size.