SiAlONs are ceramic alloys based on the elements silicon (Si), aluminium (Al), oxygen (O) and nitrogen (N) and were developed in the 1970s to solve the problem of silicon nitride (Si3N4) being difficult to fabricate.
As alloys of Si3N4, SiAlONs exist in three basic forms. Each form is isostructural with one of the two common forms of Si3N4, beta (β) and alpha (α) and with silicon oxynitride. The relationship between that of SiAlON and Si3N4 is similar to that between brass and pure copper. In the latter case, copper atoms are replaced by zinc to give a better and stronger alloy than the mother metal. In the case of SiAlON, there is substitution for Si by Al with corresponding atomic replacement of N by O, to satisfy valancy requirements. The resulting 'solution' (SiAlON) has superior properties to the original pure solvent (silicon nitride).