Equiaxed β–Si 3 N 4 ceramics prepared by rapid reaction‐bonding and post‐sintering using TiO 2 –Y 2 O 3 –Al 2 O 3 additives

Sintered reaction‐bonded Si 3 N 4 ceramics with equiaxed microstructure were prepared with TiO 2 –Y 2 O 3 –Al 2 O 3 additions by rapid nitridation at 1400°C for 2 hours and subsequent post‐sintering at 1850°C for 2 hours under N 2 pressure of 3 MPa. It was found that α–Si 3 N 4 , β–Si 3 N 4 , Si 2 N 2 O, and TiN phases were formed by rapid nitridation of Si powders with single TiO 2 additives. However, the combination of TiO 2 and Y 2 O 3 –Al 2 O 3 additives led to the formation of 100% β–Si 3 N 4 phase from the nitridation of Si powders at such low temperature (1400°C), and the removal of Si 2 N 2 O phase. As a result, dense β–Si 3 N 4 ceramics with equiaxed microstructure were obtained after post‐sintering at high temperature.