This document discusses various types of imperfections that can occur in crystal structures, including point defects (vacancies, self-interstitials, substitutional impurities), line defects (dislocations like edge and screw dislocations), and planar defects (grain boundaries, twin boundaries, stacking faults). It provides examples of each type of defect, diagrams to illustrate defects like vacancies, interstitials, and different types of dislocations, and brief explanations of defects like Frenkel defects and Schottky defects. The document also mentions defects leading to properties like specific heat and electrical resistance, and discusses concepts like slip and twinning during plastic deformation.

1. Material Science
Imperfections In Crystals
By
Sandip Thorat
Mechanical Engg. Department
SRES, Sanjivani College of Engineering,
Kopargaon. (MS) 423603
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2. Imperfections In Crystal –
1. Lattice Vibrations or Phonons or volume defect: –
- Vibration of atoms @ their mean position
-Frequency of vibration depends on temp.
-Specific heat and electrical resistance of
material.
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3. 2. Point Defect or zero dimensional Defect:-
-Due to Vibration and Temp braking of bonds
-Atoms are free from their lattice sites.
• The simplest of the point defect is a vacancy,
or vacant lattice site.
• All crystalline solids contain vacancies.
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4. A)Vacancy: vacant atomic sites in a structure.
B) Self-Interstitials: -"extra" atoms positioned between atomic sites.
Vacancy
distortion
of planes
self-
interstitial
distortion
of planes
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5. C) Substitutional impurity atoms :
Foreign material occupies position of parent atom .
D) Frenkel Defect:
 Cation (being smaller) get displaced to interstitial voids
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6. E) Schottky defect- Pair of anion and cation vacancies
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7. • Frenkel Defect
--a cation is out of place.
• Shottky Defect
--a paired set of cation and anion vacancies.
Shottky
Defect:
Frenkel
Defect
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8. A part of line of atoms will be missing from its regular site
this missing row –dislocation.
A) Edge dislocation:
- extra half-plane of atoms inserted in a crystal structure
b (the berger’s vector) is  (perpendicular) to dislocation line
3.Line Defects-
Burger’s vector, b: It indicates amount and direction of shift of the
lattice on the slip plane.
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9. B) Screw dislocation:
– Due to shearing of one part of crystal wrt other parallel to cut.
– spiral planar ramp resulting from shear deformation
– b is  (parallel) to dislocation line
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10. 10
Edge, Screw, and Mixed
Dislocations
Adapted from Fig. 4.5, Callister 7e.
Edge
Screw
Mixed

11. A) Grain Boundaries-
– Observed during Solidification of
polycrystaline materials.
4.Planar Defects in Solids
grain boundary
surface groove
polished surface
(a)
• are imperfections,
• are more susceptible
to etching,
• may be revealed as
dark lines,
• change in crystal
orientation across
boundary.
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12. B) Twin Boundaries-
– Essentially a reflection of atom positions across the twinning plane.
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13. C. Stacking Fault:-
Extrinsic stacking fault Intrinsic stacking faultPerfect stacking
B
A
A
B
AA
A
B
A
B
A
A
B
AA
A
B
A
B
A
A
B
AA
A
B
A
CC
C
B
C
C
B
C
B
A
B
AA
A
B
CC
C
B
C
B
CC
AA 13

14. 2. Grain Boundaries
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15. Elastic and Plastic Deformation
Slip:- A permanent displacement of one part of
crystal relative to other.
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16. Twinning:-
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