Aluminiumnitride

Aluminum nitride (AlN) is an inorganic compound composed of aluminum and nitrogen. It forms a white ceramic material with a hexagonal wurtzite crystal structure and is valued for its combination of high thermal conductivity, electrical insulation, and stability at elevated temperatures.

In bulk form, AlN has a very high melting point (about 2,200°C) and a wide band gap of roughly 6.0 eV, making it an excellent insulator for high-temperature and high-power applications. Its thermal conductivity is among the highest for ceramics, typically reported around 140–180 W/m·K for high-quality material. AlN also exhibits a relatively high dielectric constant (approximately 8–9) and low thermal expansion, though these properties can vary with crystal quality and microstructure. The material is chemically robust but hydrolyzes in water or humid air, releasing ammonia over time.

Production and processing of AlN usually involve direct nitridation of aluminum or aluminum compounds in a nitrogen-containing environment to form AlN powder, followed by densification through hot pressing, spark plasma sintering, or related methods. Small amounts of sintering aids, such as yttria, are commonly used to enhance densification and limit grain growth. For thin films and epitaxial layers, AlN can be grown by various chemical vapor deposition techniques (MOVPE/MOCVD or HVPE) on substrates such as sapphire, silicon carbide, or silicon.

Applications of aluminum nitride center on its role as a substrate and heat spreader in electronics, particularly for GaN-based devices and deep ultraviolet LEDs, where lattice compatibility and high thermal conductivity are advantageous. It is also used in high-temperature electronics, ceramic insulators, and certain metal matrix composites.

Safety considerations include the potential health hazard of AlN dust; the material can release ammonia upon hydrolysis, so appropriate handling and ventilation are advised.