Aluminium oxide - Al2O3

Aluminium oxide occurs as a natural raw material in its thermodynamically stable phase (corundum or alpha-Al₂O₃) and also in monocrystalline form as sapphires or rubies created by the embedding of different metallic salts. In addition to naturally-occurring or artificially-produced alpha-Al₂O₃ (sintered corundum), gamma-Al₂O₃(alumina) and beta-Al₂O₃ (as an ionic conductor) are also used in engineering ceramic applications.

Aluminium oxide is one of the most important oxide ceramic materials and finds use in probably the broadest number of engineering applications. Aluminium oxide ceramics are distinguished by their extreme hardness, strength and temperature stability and exhibit a high degree of resistance to wear and corrosion, even at high temperatures. They are also excellent electrical insulators, while simultaneously acting as adequate thermal conductors (in a densely sintered condition). However, they demonstrate poor resistance to fracturing, making Al₂O₃ components sensitive to impact and edge loading.

The favourable price/performance ratio of this material has contributed considerably to the broad distribution of aluminium oxide uses, particularly for structured ceramics. Typical examples of applications where aluminium oxide is used include:

 

Minimising the porosity and controlled utilisation of grit size enables the manufacture of transparent elements from aluminium oxide. These are used as pistons in high-pressure discharge lamps (e.g. in beamers). Transparent Al2O3 is also used in ballistic protection.