What Is The Crystal Structure Of Aluminium Nitride?

Aluminium nitride (AlN) has a hexagonal crystal structure, with the lattice parameters a = 3.112 Å and c = 4.982 Å. The unit cell of AlN is shown in Figure 1.

The crystal structure of AlN is similar to that of wurtzite-type zinc oxide (ZnO) and gallium nitride (GaN). It consists of layers of close-packed nitrogen atoms in a hexagonal arrangement, with aluminium atoms occupying octahedral sites between these layers. The aluminium atoms are coordinated by six nitrogen atoms, forming an octahedral coordination environment.

The hexagonal unit cell of AlN contains two formula units, with four aluminium atoms and four nitrogen atoms arranged in a zigzag pattern along the c-axis. The Al-N bond length is 1.77 Å, which is shorter than the corresponding bond length in GaN (1.86 Å), indicating a stronger bond in AlN.

AlN has a high thermal conductivity, low thermal expansion coefficient, and excellent electrical insulation properties, making it an attractive material for electronic and optoelectronic applications such as substrates, heat sinks, and high-power electronic devices.