Ceramics

Ceramics

• are materials derived from the Greek word keramikos (“burnt stuff”).

Electrically charged ions

ceramics are composed of what ions?

Two elements

Ceramics are typically made of at least how many elements?

• Shaping and drying

• Kiln drying (about 1000°C)

• Cooling

Typical steps for traditional pottery:

Ionic Ceramics

Strong ionic bonds

Covalent ceramics

ceramics with covalent bonds

Electrically neutral

The magnitude of component charges of crystal must be what?

Higher coordination number

Higher ratios means what?

Slip

Crystalline Ceramics deforms by?

• Strong bonds

• complex loose structure (low APF)

• Complex dislocation structures

Slip in Crystalline ceramics are very difficult due to what?

Amorphous Ceramics (Glass)

Ceramics that are almost perfectly elastic until fracture

• lack of disloacations (no slip & plastic deformation)

Amorphous ceramics are very brittle due to what

Viscous flow

Deformation of amorphous ceramics happens by?

Below glass transition temperature

Glass is highly viscous and barely flows at what temperature?

Strength and toughness

Tempering increases what property of glass

Frenkel defect

Defect where there is action vacancy and action interstitial pair and no net charge change

Schottky defect

Cation vacancy and anion vacancy pair

Maintains charge neutrality

Impurity Ions

Interstitial impurity ions

Substitutional impurity ions

Non Stoichiometric Compounds

Deviations from exact cation:anion ratios

• formation energy (),

• Boltzmann constant (),

• temperature (), and

• total number of lattice sites ()

Equilibrium number of defects depends on what

Rock Salt Structure

structure where coordination number for both cation and anion is 6 where the unit cell is FCC arrangement of anions with cation situated at center and one at the center of the 12 cube edges

cesium chloride structure

coordination number for both cation and anion is 8 where anions are lovatrd at esch corners of a cube anf the cube center is a single cation

Zinc blende structure

coordination number for both is 4 and all corner and face position are occupird by anions where cations fill interior tetrahedral position

Fluorite stucture

cation has 8 and anion has 4. one unit cell is composed of 8 cubes where cations are at the center and anions at the corners

perovskite structure

Ba ions are situated at all eight corner of the cube and single Ti ions is at the center of the cube with O2 ions located at the center of each faces