Responding to Temperature Changes

Abstract

Heat is essentially the vibration of atoms in a material. Consequently thermal properties reflect the type and strength of interatomic bonding and the crystal structure. The important thermal properties of any material are

• Heat capacity

• Coefficient of thermal expansion

• Thermal conductivity

Thermal properties of ceramics differ from those of metals whenever free (conduction) electrons are involved, such as in thermal conductivity. However, heat transfer by phonon (lattice vibration) transport can in some cases be more effective than through the movement of electrons. We describe melting and vaporization of ceramics as the temperatures for these transformations tend to be high, which can be critical in certain applications, such as the tiles on the space shuttle, but present problems during processing. It should also be obvious by now that heat affects many of the properties of ceramics such as Young’s modulus, electrical conductivity, magnetic behavior, and dielectric constant. There are major applications that utilize the varied thermal properties of ceramics, from high thermal conductivity substrates for electronic packaging to enormous mirror blanks for telescopes that have “zero” expansion.