This document discusses various types of defects that can occur in crystal structures, categorizing them based on dimensionality. Point defects are irregularities around a single atom and include vacancies, interstitials, Frenkel defects, and Schottky defects. Line defects distort atomic bonds around a dislocation line and include edge and screw dislocations. Surface defects occur at grain boundaries where crystal orientations change. Bulk defects in the volume of the material include precipitates, dispersants, inclusions, and voids. Defects can impact material properties and are sometimes deliberately introduced to improve characteristics.

1. DEFECTS IN CRYSTALS
“Crystals are like people, it is the defects
in them which tend to make them
interesting!” - Colin Humphreys
MADE BY – VIKASH PRASAD
S.E. ELECTRICAL
PVG’S COET PUNE

2. INTRODUCTION
• Crystalline material has a crystal structure in
which the atoms are positioned in perfect
ordered pattern which is repetitive over large
atomic distance.
• Defects have a profound impact on the
macroscopic properties of materials.
• Sometimes defects are deliberately created to
improve properties of crystal.

3. CLASSIFICATION OF DEFECTS BASED ON DIMENSIONALITY
0D
(Point defects)
1D
(Line defects)
2D
(Surface / Interface)
3D
(Volume defects)
Vacancy
Interstitial
Frenkel
defect
Schottky
defect
Edge
Dislocation
Grain
boundary
Twin
boundary
Dispersant
Precipitate
Inclusion
Voids /
Stacking Cracks
faults
Screw
Dislocation

4. POINT DEFECTS
Point Defects are the irregularities or deviations
from ideal arrangement around a point or an
atom in a crystalline substance.
0D
(Point defects)
Vacancy
Interstitial
Frenkel defect
Schottky defect
Non-ionic
crystals
Ionic
crystals

5. VACANCY DEFECT
Missing atom
 Atom missing from an atomic site
 Occur due to imperfect packing during crystallisation
 This results in decrease in density of the substance
 Number of vacancy defects depend on temperature

6. INTERSTITIALS DEFECT
Interstitial atom
 Addition of an extra atom within a crystal structure
 This defect increases the density of the substance
 Causes atomic distortion
 Vacancy and interstitials are inverse phenomena

7. SCHOTTKY DEFECT
 Pair of anion and cation vacancies
 In order to maintain electrical neutrality, the number of missing
cations and anions are equal
 It also decreases the density of crystal
 E.g. Alkali halides such as NaCl, KF, etc.

8. FRENKEL DEFECTS
 Cation (being smaller get displaced to interstitial voids
 Combination of vacancy and interstitial atom
 No change in the density
 E.g. AgI, CaF2

9. LINE DEFECTS
• Line defects are the irregularities or deviations from
ideal arrangement in entire rows of lattice points.
• Interatomic bonds significantly distorted in
immediate vicinity of dislocation line.
• Dislocation affects the mechanical properties.

10. EDGE DISLOCATION
• POSITIVE DISLOCATION
• NEGATIVE DISLOCATION
SCREW DISLOCATION
The lattice/atomic planes
follow helical or spiral
along the dislocation line.

11. SURFACE DEFECTS
• Surface defects are associated with boundaries
that are separate regions of the materials and
have different crystal structure.
• Two Dimensional defect.
• Due to change in orientation of the atomic
planes and stacking sequence of atomic planes.
• Caused during solidification or mechanical or
thermal treatment of material.
• Effect the mechanical properties, electrical
resistance and corrosion resistance.

12. Bulk or Volume Defects
 PERCIPITATES : Fraction of a micron in size
 DISPERSANTS : may be large precipitates, grains, or polygranular
particles distributed through microstructure
 INCLUSIONS : foreign particles or large precipitate particles ;
undesirable ; harmful
 VOIDS : Trapped Gases ; Decreases mechanical strength
Cluster of microcracks in a
melanin granule irradiated
by a short laser pulse.

13. THANk
you
...Perfection's a gift of
The gods , few can boast they possess it - and most
Of you, my dears, don't .
- Ovid