The advantages and applications of Aluminum Nitride

Aluminum Nitride (AlN), a covalently-bonded ceramic, is synthesized from the abundant elements aluminum and nitrogen. It does not occur naturally.AlN is stable in inert atmospheres at temperatures over 2000°C. It exhibits high thermal conductivity but is, uniquely, a strong dielectric. This unusual combination of properties makes AlN a critical advanced material for many future applications in optics, lighting, electronics and renewable energy.

Advantages

• Uniform microstructure
• High thermal conductivity* (70-180 Wm-1K-1), tailored via processing conditions and additives
• High electrical resistivity
• Thermal expansion coefficient close to that of Silicon
• Resistance to corrosion and erosion
• Excellent thermal shock resistance
• Chemically stable up to 980°C in H2 and CO2 atmospheres, and in air up to 1380°C (surface oxidation occurs around 780°C; the surface layer protects the bulk up to 1380°C).

Applications

Epitaxially grown thin film crystalline aluminium nitride is used for surface acoustic wave sensors (SAWs) deposited on silicon wafers because of AlN's piezoelectric properties. One application is an RF filter which is widely used in mobile phones,which is called a thin film bulk acoustic resonator (FBAR). This is a MEMS device that uses aluminium nitride sandwiched between two metal layers.

Aluminium nitride is also used to build piezoelectric micromachined ultrasound transducers, which emit and receive ultrasound and which can be used for in-air rangefinding over distances of up to a meter.

Metallization methods are available to allow AlN to be used in electronics applications similar to those of alumina and beryllium oxide. AlN nanotubes as inorganic quasi-one-dimensional nanotubes, which are isoelectronic with carbon nanotubes, have been suggested as chemical sensors for toxic gases.

There are also multiple research efforts in industry and academia to use aluminum nitride in piezoelectric MEMS applications. These include resonators, gyroscopes and microphones.