During the materials selection process for ceramics, engineers and designers often come across the term 'SiAlON' - often very close or related to a description of silicon nitride materials. This is quite understandable: SiAlONs are a solid solution of silicon, aluminium, oxygen and nitrogen - the name is revealed when the chemical symbols for these elements are put together.
In reality, SiAlONs are mixtures of alumina (Al2O3) and silicon nitride (Si3N4); alumina is able to substitute itself, to a limited extent, into the structure of the silicon nitride. The result is that the material exhibits the best quality of both parents in terms of properties such as thermal shock and corrosion resistance.
In addition, some grades of SiAlON have deliberate additions of electrically conducting secondary phases, making these grades of SiAlON machinable using electro-discharge machining (EDM).