How Is Aluminium Nitride Synthesized?

Aluminium nitride (AlN) is typically synthesized using one of two methods:

1. Direct Nitridation: In this method, aluminium metal or aluminium oxide is reacted with nitrogen gas at high temperatures (>1000°C) in the presence of a catalyst such as lithium or sodium. The reaction can be represented by the following chemical equation:

2 Al + N2 → 2 AlN

Alternatively, aluminium hydroxide can also be used as the starting material instead of aluminium metal or oxide. The direct nitridation method produces high-quality AlN powders with good crystallinity and purity.

2. Carbothermal Reduction: In this method, a mixture of aluminium oxide and carbon is heated to high temperatures (>1600°C) in a nitrogen atmosphere. The carbon reduces the aluminium oxide to metallic aluminium, which then reacts with the nitrogen gas to form AlN. The reaction can be represented by the following chemical equation:

Al2O3 + 3 C + N2 → 2 AlN + 3 CO

This method is more commonly used for synthesizing bulk AlN materials such as wafers and substrates rather than powders. The carbothermal reduction method can produce large, high-purity AlN crystals, but the process is more complex and expensive compared to direct nitridation.