ABSTRACT
Density (ρ) is a measure of the mass (m) per unit volume (V) of a material and is reported in units such as grams per cubic centimeter or pounds per cubic inch. Several factors influence density: the size and atomic weight of the elements, the tightness of packing of the atoms in the crystal structure, and the amount of porosity in the microstructure. The term density can be used in various ways, each with a different meaning. To be sure of the correct meaning, we need to use modifying words:
1. Crystallographic density: the ideal density of a specific crystal structure calculated from chemical composition data and from inter-atomic spacing data obtained by x-ray diffraction
2. Theoretical density: the density of a material that contains zero microstructural porosity (takes into account multiple phases, defect structures, and solid solution)
3. Bulk density: the measured density of a bulk ceramic body (includes all porosity, lattice defects, and phases)
4. Specific gravity: the density of a material relative to the density of an equal volume of water at 4°C (usually based upon crystallographic or theoretical density).
