From cyclotetrasilazane [(CH3)2SiNH]4 via crystalline silicon nitride imide Si2N2NH to α‐Si3N4

Abstract α‐Si3N4 is synthesized by an ammonia thermal synthesis using a cyclic oligosilazane, [(CH3)2SiNH]4, as the starting material. [(CH3)2SiNH]4 reacts in the presence of ammonia at 900°C and 80 MPa pressure to give silicon nitride imide (Si2N2NH). Subsequently, Si2N2NH is converted into α‐Si3N4 by thermal decomposition at 1500°C and 0.1 MPa nitrogen with the simultaneous loss of NH3.