Preparation, microstructure, and mechanical property relationships in silicon nitride based ceramics

摘要

Two commercial Si_3N_4 powders and several sintering aid systems (AlN + Y_2O_3; Al_2O_3 + Y_2O_3; La_2O_3 + Y_2O_3) were chosen to produce fully dense materials to investigate the relationships between the preparation methods, microstructure, and mechanical properties of some silicon nitride ceramics. Correlations between the aspect ratio and grain size, grain boundary phase characteristics and Young's modulus, hardness, strength, and fracture toughness are discussed. The study was focused on crack propagation and grain boundary toughness in order to contribute to the understanding of the fracture resistance of silicon nitride based ceramics.