Reaction bonded and post-sintered silicon nitride ceramics was fabricated using ZrO2-MgAl2O4 as sintering additives. It was clarified that added ZrO2 was act as nitridation enhanced effect under MgAl2O4 coexistence during reaction bonding process, and nitridation of the silicon was also completed lower temperature than that of Silicon without ZrO2-MgAl2O4. The post-sintered specimen had a four-point bending strength of 850 MPa, which was obtained same fracture strength at same additive system prepared using high purity silicon nitride powder as a starting material.
