Aluminium Oxynitride

Aluminium Oxynitride

Aluminium oxynitride is a transparent ceramic made up of aluminium, oxygen, and nitrogen. It is a ceramic substance that combines the characteristics of alumina and aluminum nitride. It is commonly utilized in applications that demand a translucent, durable material with high strength and hardness.

It has optical transparency (≥80%) in the near-ultraviolet, visible, and mid-wave-infrared areas of the electromagnetic spectrum. It is four times as hard as fused silica glass, 85% harder than sapphire, and over 115% harder than magnesium aluminate spinel. It can be processed into transparent windows, plates, domes, rods, tubes, and other shapes using standard ceramic powder processing methods.


Aluminium oxynitride is the hardest polycrystalline transparent ceramic available commercially. Because of its relatively low weight, distinctive optical and mechanical properties, and resistance to oxidation or radiation, it shows promise for applications such as bulletproof, blast-resistant, and optoelectronic windows.

  • Chemical formula: (AlN)x·(Al2O3)1−x, 0.30 ≤ x ≤ 0.37
  • Appearance: White or transparent solid
  • Density: 3.691–3.696 g/cm3
  • Melting point: ~2150 °C
  • Solubility in water: insoluble
  • Refractive index (nD): 1.79
  • Crystal structure: cubic spinel

Aluminum oxynitride is a very hard ceramic substance. It is commonly utilized as a transparent armor material in military applications to guard against projectiles and ballistic threats. It has excellent strength and toughness, which makes it resistant to mechanical impact and wear. This feature, paired with its hardness, enhances its usefulness in protective applications.

Aluminium oxynitride has excellent thermal conductivity. This characteristic is significant in applications where efficient heat dissipation is required. It is an electrical insulator, hence it is appropriate for applications that require electrical insulation. The coefficient of thermal expansion is relatively low. This characteristic is useful in applications that require dimensional stability across a wide range of temperatures.


Aluminium oxynitride is utilized in infrared-optical windows because it has more than 80% transparency at wavelengths less than about 4 micrometers and nearly zero at about 6 micrometers. It has also been used as an interface passivation layer in certain semiconductor-related applications.

Aluminium oxynitride is significantly lighter and thinner than glass-based transparent armor. Aluminium oxynitride armor with a thickness of 1.6 inches (41 mm; 4.1 cm) can withstand.50 BMG armor-piercing rounds that can penetrate 3.7 inches (94 mm; 9.4 cm) of standard glass laminate.