Aluminum nitride, or AIN, is one of the post-transition metal nitrides and is an inorganic compound with chemical formula AlN. It has a crystal structure that is hexagonal and it is an electrical insulator in its natural state. However, it can be doped to allow it to behave as a semiconductor and has a wide band gap at room temperature that could potentially make it useful in deep ultraviolet optoelectronics.
It is a newer material in the technical ceramics family and was only discovered over 100 years ago, although it has been made into a commercially viable product with controlled properties within the last 20 years. Its thermal conductivity is nine times greater than alumina and it is used in several applications such as thermocouple insulators, evaporation boats, grinding media, and crystal growing crucibles. The market is expected to grow owing to its use in power electronics, and as a substitute for tungsten carbide in high-speed tools.
The structure of AlN is based on ionic bonds and therefore it does not exist as individual molecular units like water or other molecules do. Instead, an ionic compound has a large three-dimensional array of cations and anions arranged in a tetrahedral coordination. When writing the chemical formula for ionic compounds it is important to write the symbol of the metal cation and then the non-metal anion, crisscrossing their ion charges to make sure that the final formula is neutral. For example, zinc phosphate is composed of three zinc cations with 2+2+ charges balancing out two phosphate anions with 3-3- charges.