Crystal Structures & their imperfection
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Transcript of Crystal Structures & their imperfection
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Crystal Structures & their Imperfections
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A REGULAR THREE DIMENSIONAL ARRANGEMENT OF CONSTITUENT PARTICLES REPRESENTED BY POINT IN SPACE, IS KNOWN AS CRYSTAL LATTICE.
THERE ARE ONLY 14 THREE DIMENSIONAL LATTICES WHICH ARE KNOWN AS BRAVAIS LATTICES
CRYSTAL LATTICE
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UNIT CELL
The Smallest portion of a crystal lattice is known as Unit Cell which when repeated in different direction generates the complete lattice.
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TYPES OF CRYSTAL SYSTEMThere are 7 types of Crystal Systems :-
● Cubical Crystal System
● Tetragonal Crystal System
● Hexagonal Crystal System
● Rhombohedral Crystal System
● Orthorhombic Crystal System
● Monoclinic Crystal System
● Triclinic Crystal System
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CUBIC CRYSTAL SYSTEM
Axial Relationship -> a=b=cInter axial angle -> α=β=γ
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HEXAGONAL CRYSTAL SYSTEM
Axial Relationships -> a=b≠c Inter axial Angles -> α=β=90̊3, γ=120̊
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TETRAGONAL CRYSTAL SYSTEM
Axial Relationships -> a=b≠cInter axial Angles -> α=β=γ=90̊3
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RHOMBOHEDRAL CRYSTAL SYSTEM
Axial Relationships -> a=b=c Inter axial Angles -> α=β=γ≠90̊3
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ORTHORHOMBIC CRYSTAL SYSTEM
Axial Relationships -> a≠b≠cInter axial angles -> α=β=γ=90̊3
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MONOCLINIC CRYSTAL SYSTEM
Axial Relationships -> a≠b≠cInter axial Angles -> α≠90̊3 , β=γ=90̊3
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TRICLINIC CRYSTAL SYSTEM
Axial Relationships -> a≠b≠cInter axial Angles -> α≠β≠γ≠90̊3
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DEFECTS IN SOLIDS
Vacancy Defect - This defect develops in any crystal when some lattice sides are empty. As a result, the density of the substance decreases.
This Defects may develops when some substance heated.
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DEFECTS IN SOLIDS
Interstitial Defect – This defect develops when some constituents particles occupy interstitial sides. Due to this defects, the density of the crystal increases.
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DEFECTS IN SOLIDS
Frenkel Defect – In this Defect smaller ion (cation) is dislocated from its original sides to an interstitial sides due to which vacancy defect is developed at its original location.
It is also called with the name Dislocation Defect.
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DEFECTS IN SOLIDS
Schottky Defect – This defect develops when some cation & anion are missing from their lattice sides due to which the crystal remain neutral. So, it is a vacancy defect in ionic solid.
Due to Schottky Defect, the density of the crystal decreases.
This defect is shown by those ionic crystal solids in which the cations & anions are of almost similar sizes.
AgBr shows both frenkel & Schottky Defect.
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