Lecture 9

Question 1

What are point defects?

Answer 1

Vacancy atoms, Interstitial atoms,
Substitutional atoms

Question 2

What are line defects?

Answer 2

. Line defects: Dislocations

Question 3

What are area defects?

Answer 3

Area defects: Grain boundaries

Question 4

What are vl defects?

Answer 4

Volume defects: Cracks, pores, inclusions

Question 5

Define the imperfections that can be found within ceramics

Answer 5

Point defects - defined as deviations from the perfect
atomic arrangement.
(1) Missing ions
(2) Substituted ions
(3) Interstitial ions (extra atoms)
(4) Associated valence electrons

Question 6

Define Electroneutrality and should it be maintained?

Answer 6

state that
exists when there are equal numbers
of positive and negative charges
from the ions.

Yes, electroneutrality should be maintained.

Question 7

Frekel Defect

Answer 7

• cation vacancy and a cation
  interstitial pair
• theory of the vibrational translational movement of molecules in liquids and amorphous bodies
• cation leaving its normal position and moving into an interstitial site.

Question 8

Schottky Defect

Answer 8

-Cation vacancy

– anion vacancy
pair

-Both cations and anions have the same
charge,

• the charge neutrality of the crystal is maintained

Question 9

Nonstoichiometry

Answer 9

ceramic materials in which
two valences (or ionic) states exist for one of the ion types

Question 10

equilibrium numbers of both Frenkel and Schottky defects….

Answer 10

increase with and depend on the temperature in a manner similar to the number of vacancies in metals.

Question 11

Equilibrium number of defects

Answer 11

N: The total number of lattice sites
𝑄fr or 𝑄s
: The energy required for the formation of each Frenkel or Schottky
defects
k: Boltzmann constant
T: Absolute temperature