There are several types of defects that can occur in crystalline materials, including point defects, line defects, and grain boundaries. Point defects include vacancies, interstitial atoms, and substitutional/interstitial impurities. Line defects include stacking faults which occur when the regular stacking sequence of atomic planes is disturbed. Grain boundaries separate crystalline grains of different orientations in polycrystalline materials. These defects influence many properties of materials.

1. Defects In Crystalline
Materials.

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3. Defects In Crystalline Materials.
 Metals, many ceramics and some
polymers are crystalline.
 Real crystals contain various types of
imperfections.
 Many of the important properties of
materials are due to the presence of these
imperfections.

4. Types Of Defects.
 Defects are categorized as:
1) Point defects.
2) Surface defects.
3) Volume defects.
4) Line defects.

5. Point Defects.
 All the atoms in a perfect lattice are at
specific atomic site.
 In a pure metal two types of point defects
are possible.
1) Vacancies.
2) Interstitial point defects.

6. Vacancies.
 Vacant atomic sites in
a structure.
 Due to plastic
deformation & high
energy particle
irradiation.

7. Interstitial Point Defects.
 “Extra" atoms positioned between atomic
sites.
 Due to plastic deformation & high energy
particle irradiation Interstitial
atom
distortion
of planes

8. Extrinsic Point Defects.
 Introduction of outsider atom.
 They play an important role in physical &
mechanical properties.
 Impurity atom can take two different sites
in crystal.
 Substitutional or Interstitial.

9. Point Defects
vacancy Interstitial
impurity
Substitutional
impurity

10. In metallic solids defects are not so
important but in ionic solids presence of a
vacant site (e.g. in NaCl), changes the
electrical properties.

11. Schottky & Frenkel Defects
 In order to conserve the overall neutral
charge vacancy must be occurred either in
pairs of opposite sign forming die-
vacancies called Schottky defects.
 In association of the interstitial of same ion
called Frenkel defects.

12. Defects in ionic solids
Frenkel
defect
Cation vacancy
+
cation interstitial
Schottky
defect
Cation vacancy
+
anion vacancy

13. Stacking Faults.
 Stacking fault is a planner defect and formed
when regular sequence of stacking is disturbed.
 Stacking faults are not may observed In planes
where the stacking sequence is
ABABAB….because there is no alternative site
for “A” layer other than resting on a “B” layer of
vice versa.
 In ABCABABC….layers it is visible.

14. A
B
C

15. Types Of Stacking Faults.
1) Intrinsic stacking faults.
2) Extrinsic stacking faults.

16. Intrinsic Stacking Faults.
 Removal of a layer from an arranged
sequence layer.
 E.g. CBACBA…..becomes CBABAC….

17. Extrinsic Stacking Faults.
 Addition of layer to the arranged sequence
layer.
 E.g. BACBAC….becomes BACABAC…

18. Grain Boundaries.
 A Grain Boundary is a general planar
defect that separates regions of different
crystalline orientation (i.e. grains) within a
polycrystalline solid.
 The atoms in the grain boundary will not
be in perfect crystalline arrangement

19. Grain Boundaries Cont...
 Grain boundaries are
usually the result of
uneven growth when
the solid is
crystallizing.