Microstructure and properties of Si₃N₄ ceramics obtained from addition of β-phase seeds and celsian

The silicon nitride based ceramics obtained by the addition of β-Si₃N₄ seeds was fabricated using celsian as the additive and by pressureless sintering. The microstructure of the material was observed and analyzed using XRD,SEM,and TEM and the mechanical response of this array microstructure was characterized for flexural strength and fracture behavior. The result shows that the growth of the larger aspect ratio grains initiate mainly from the seeds through the heterogeneous nucleation mechanism during the process of phase transformation,and the intergranular phase BaAl₂Si₂O₈ services as good refractory materials. In contrast to conven-tional processing,a stable bimodal microstructure and complicated component with a lower cost can be achieved using the above-mentioned process theoretically and practically.