Relationship between Microstructure and Mechanical Properties for Silicon Nitride Based Ceramics Fabricated by PECS

摘要

Silicon nitride ceramics with various α/β-gratio were fabricated by Pulse Electric Current Sintering (PECS). As a sintering additives Y2O3 and Al2O, were used. Densified Si3N4 materials which have over 99. relative density were obtained by controlling the sintering conditions and their pphase ratio was over 20 vol. The effect of α/β ratio was investigated with respect to hardness, strength, Young's modulus and toughness for the densified Si3N4 ceramics. The change of microstructure with diferent α/β-ratio was also ohserved by SEM. The fracture strcngth increased with increasing ,2-phase up to 6080 of β-content, and after saturation, decrcased with increasing β -phase. These results were closely related to variation of fracture toughncss and microstructure. Futhcrmore, the SiC particle was disperscd into Si3N4 ceramics and the effects of SiC dispersion on α /β-ratio, microstructure and mechanical properties were investigatcd.