Frankel and Schottky defects occur in ionic crystals when ions leave their lattice sites. Frankel defects occur when an ion leaves its site and occupies an interstitial site, maintaining electrical neutrality and stoichiometry. Examples include AgCl and AgBr. Schottky defects occur when both cation and anion ions leave their lattice sites, creating vacancies that decrease the crystal's density. Examples include NaCl and KCl. The key difference between the defects is that Frankel defects do not change density while Schottky defects do due to vacancies formed by both ion types leaving lattice sites.

1. TOPIC :- Frankel and Schottky Defect
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2. If an ion left its lattice site (causing a vacancy or
a hole there) and occupies the interstitial site,
electrical neutrality as well as stoichiometry of the
compound are maintained.
This effect does not cause effect on density of
crystal as no ion lefts the crystal.
Examples of such compounds:-
AgCl , AgBr , etc.
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3. TYPES OF
COMPOUNDS
EXHIBITS
FRANKEL
DEFECTS
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Low
Coordination
number
Large Difference
between size of
cation and anion

4. The smaller ion lefts the lattice sits and shifted
towards an interstitial site which cause a hole
there. This is Frankel Defect
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5. 5

6. SCHOTTKY
DEFECT
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In ionic crystals, the defect forms when
oppositely charged ions leave their lattice sites,
creating vacancies. These vacancies are formed in
stoichiometry units, to maintain an overall neutral
charge in the ionic solid. The vacancies are then free
to move about as their own entities. Normally these
defects will lead to a decrease in the density of the
crystal.
For examples in compounds :-
NaCl , KCl , AgBr etc.

7. Types of
Compounds
Exhibits
Schottky
Defects
Low Coordination
number
Small Difference
size between of
cation and anion
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8. In this both cation and anion lefts there lattice site
and moves out of crystal and left a vacancy there.
This is Schottky Defect.
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9. NaCl is an
example of
Schottky
Defect where
both Na+ and
Cl- left the
crystal.
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10. SOME OTHER CONSEQUENCES OF FRANKEL
AND SCHOTTKY DEFECTS
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• Solids with these defects conduct
electricity at a small extent.
• Stability of crystal decreases.
• Increase in dielectric constant of crystal.

11. MAIN DIFFERENCES BETWEEN SCHOTTKY
DEFECT AND FRANKEL DEFECT
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Schottky Defect 1. Frankel Defect
It is due to equal number of cations
and anions missing from lattice
site.
It is due to missing of ion from
lattice site and occupies the
interstitial site.
This results in decrease of density
of the crystal.
This has no effect on density.
This type of defect is found in
highly ionic compounds with
high coordination number.
This type of defect is found in
crystals with low coordination
number.
For Example:- NaCl , CsCl etc. For example:- AgCl , AgBr etc.