Ceramics, Glasses, and Electronic Materials Flashcards

The primary bonding type in most ceramic materials is:

Answer: Ionic and/or covalent bonding

Ceramics are held together by ionic bonds (in oxides), covalent bonds (in carbides/nitrides), or a combination of both, which explains their high hardness and brittleness.

Which defect in a crystalline ceramic consists of a cation vacancy paired with an anion vacancy to maintain electrical neutrality?

Answer: Schottky defect

A Schottky defect consists of a paired cation-anion vacancy that maintains charge neutrality in the crystal.

The main reason ceramics are brittle compared to metals is:

Answer: Lack of mobile dislocations due to strong directional bonding and large unit cells

Ceramics have strong ionic/covalent bonds and complex crystal structures that make dislocation motion energetically very difficult, preventing plastic deformation and causing brittleness.

Silica glass (SiO2) has an amorphous structure because:

Answer: Rapid cooling from the melt prevents long-range atomic ordering

Silica glass is formed by cooling the melt rapidly enough that the SiO4 tetrahedra cannot arrange into a periodic crystalline lattice, resulting in a random network.

Partially stabilized zirconia (PSZ) is toughened by which mechanism?

Answer: Transformation toughening: stress-induced tetragonal-to-monoclinic phase transformation at a crack tip

In PSZ, the stress field ahead of a crack tip triggers the tetragonal-to-monoclinic transformation, which involves a volume expansion that closes the crack and absorbs energy.

In semiconductor materials, the band gap determines:

Answer: The energy required to excite an electron from the valence band to the conduction band

The band gap is the energy difference between the top of the valence band and the bottom of the conduction band; electrons must acquire this energy to become conductive.