Chapter 12

means “burnt stuff,” indicating that desirable properties of these materials are normally achieved through a high-temperature heat treatment process called firing

• metallic ionsare - positively charged because they have given up their valence electrons to the nonmetallic ions

negatively charged

• most common AX crystal structure • coordination number for both cations and anions is 6 • two interpenetrating FCC lattices—one composed of the cations, the other of anions

• coordination number is 8 - anions are located at each of the corners of a cube, whereas the cube center is a single cation

• coordination number is 4 - all ions are tetrahedrally coordinated

four atoms (three in one plane, and a single one in the adjacent plane) surround one type

six ion spheres, three in each of the two planes

• materials composed primarily of silicon and oxygen, the two most abundant elements in Earth’s crust • not considered ionic

• most simple silicate material - material is electrically neutral and all atoms have stable electronic structures

silica made to exist as a noncrystalline solid or glass having a high degree of atomic randomness, which is characteristic of the liquid

other oxides that form glassy structures

oxides that do not form polyhedral networks, their cations are incorporated within and modify the SiO4-4 network

other oxides, such as TiO2 and Al2O3 although not network formers, substitute for silicon and become part of and stabilize the network

exists in two allotropic forms—diamond and graphite—as well as in the amorphous state

metastable carbon polymorph at room temperature and atmospheric pressure

• another polymorph of carbon - furthermore, it is a stable polymorph at ambient temperature and pressure

does not belong to a specific atom or bond

designate the types and concentrations of atomic defects in ceramics

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

• type of defect involves a cation–vacancy and a cation–interstitial pair • defect where cation leaves its normal position and moves into an interstitial site

• type of defect found in AX materials & involves a cation vacancy–anion vacancy pair • removing one cation and one anion from the interior of the crystal and then placing them both at an external surface

state for ionic compounds wherein there is the exact ratio of cations to anions as predicted by the chemical formula

points at which the magnitude of an applied tensile stress is amplified and no mechanism such as plastic deformation exists to slow down or divert such cracks