TABLE OF CONTENTS Silicon carbide sensors are being developed for several demanding applications, often in the automotive and aerospace industries. The semiconducting functionality of SiC is due to its wide band gap and low intrinsic carrier concentration which, combined with other properties such as mechanical toughness and high thermal conductivity, make it an excellent material for use in harsh environments. Some properties of SiC are listed below:
Density: 3.21 10 3kg m 3.
Mohs hardness: ~9.
Melting point: ~2700 C.
Thermal conductivity: 490W mK 1.
Thermal expansion coefficient: 4-5 10 6 K 1.
Band gap: 3.27eV.
Breakdown electric field: 2-4 10 8Vm 1.
Dielectric constant: 9.7.
Further, the possibility of developing high temperature electronics from SiC may ultimately lead to sensors and electronics being located in a single package at the point of measurement, thus eliminating many leads and connectors. This is particularly important for commercial aircraft, where wiring and connector failure are crucial factors that determine engine maintenance cycles and the aircraft s downtime. SiC electronics and sensors that could operate uncooled at temperatures up to 600 C would result in substantial performance gains due to weight savings and increased reliability.
A good example of a SiC sensor operating in a harsh environment is an in-cylinder pressure sensor for a car engine, where temperatures can reach 500 C. By accurately monitoring and controlling the pressure and temperature in the combustion chamber, the engine efficiency can be raised and the fuel consumption and pollutant emissions reduced.
