Ceramic Structure and Properties Review

These flashcards cover the key vocabulary and concepts from Chapter 12 on Ceramic Structure and Properties, including crystal structures, defects, and mechanical testing.

Ceramics

Inorganic and non-metallic materials composed of compounds between metallic and non-metallic elements.

Ionic Character

The percentage of bonding that is ionic, which increases as the difference in electronegativity ($\Delta X$) between elements increases.

Coordination Number (C.N.)

The number of nearest oppositely charged neighbors surrounding an ion in a ceramic crystal structure.

Octahedral (OH) Site Ratio

A configuration where the ratio of cation radius to anion radius ($r_{cation}/r_{anion}$) falls between $0.414$ and $0.732$, resulting in a coordination number of 6.

Charge Neutrality

The requirement that the net charge in a ceramic crystal structure should be zero, represented by the general form $A_mX_p$.

Rock Salt Structure

An AX-type crystal structure with FCC anion packing and a coordination number of 6 for both cations and anions (e.g., $NaCl$, $MgO$, $FeO$).

Cesium Chloride Structure

An AX-type crystal structure with simple cubic packing and a coordination number of 8 for both cations and anions (e.g., $CsCl$).

Zinc Blende (Sphalerite) Structure

An AX-type crystal structure where the coordination number is 4 and bonding hybridization often favors tetrahedral (TD) sites (e.g., $ZnS$, $SiC$).

Fluorite Structure

An $AX_2$ crystal structure, such as $CaF_2$, where cations occupy half of the cubic sites in a simple cubic arrangement.

Perovskite Structure

A complex $ABX_3$ crystal structure involving two types of cations ($A$ and $B$), commonly found in materials like $BaTiO_3$.

Spinel Structure

An $AB_2X_4$ crystal structure with FCC anion packing, exemplified by $MgAl_2O_4$ and $FeAl_2O_4$.

Theoretical Density ($\rho$)

Calculated using the formula $\rho = \frac{n'( \Sigma A_C + \Sigma A_A)}{V_C N_A}$, where $n'$ is the number of formula units per unit cell.

Silicates

Common ceramic materials based on the strong $Si-O$ bond, including structures like quartz, crystobalite, and tridymite.

Amorphous Silica

A non-crystalline form of $SiO_2$ where atoms are not in a well-ordered lattice; examples include silica gels and silica glass.

Layered Silicates

Clay silicates where $SiO_4$ tetrahedra connect to form 2-D planes with the basic unit $(Si_2O_5)^{2-}$.

Diamond

A carbon form with tetrahedral bonding and $sp^3$ hybridization, characterized by extreme hardness and lack of good slip planes.

Graphite

A layered carbon structure with aromatic layers held by weak van der Waal's forces, allowing planes to slide easily.

Fullerenes

Carbon molecules formed by curving graphite sheets into balls (e.g., Buckminister fullerenes/Buckyballs like $C_{60}$) or tubes.

Frenkel Defect

A ceramic point defect that occurs when a cation is displaced from its normal lattice position to an interstitial site.

Schottky Defect

A ceramic point defect consisting of a paired set of cation and anion vacancies to maintain charge balance.

Electroneutrality

The condition of maintaining a zero net charge when impurities or defects are introduced into the ceramic lattice.

Flexural Strength ($\sigma_{fs}$)

A measure of the room temperature strength of ceramics, often determined via a 3-point bend test due to the difficulty of tensile testing brittle materials.

Porosity ($P$)

The volume fraction of internal pores, which reduces the elastic modulus ($E$) and flexural strength ($\sigma_{fs}$) of ceramic materials.