In Situ Measurement of Shrinkage During Postreaction Sintering of Reaction-Bonded Silicon Nitride

The reaction-bonding technique is one of the major fabrication processes of silicon nitride (Si 3 N 4 ) ceramics, which has received much attention as a cost-effective process due to the use of cheap Si powder as a raw material. Many studies on the development of this method have been performed in order to improve their properties; however, the sintering shrinkage behavior, which is a very important information to optimize the firing condition, has not been well clarified. In this study, we focused on the reaction-bonding technique of the Si-Y 2 O 3 -Al 2 O 3 system. At first, reaction-bonded body of the Si-Y 2 O 3 -Al 2 O 3 system was prepared, and then its postreaction sintering shrinkage behavior was investigated by in situ dilatometry. It was found that no shrinkage occurred from 1400° to 1600°C due to grain rearrangement in the reaction-bonded Si 3 N 4 body. Furthermore, the shrinkage of the reaction-bonded Si 3 N 4 started around 1750°C, which is a higher temperature compared with the green body of conventional Si 3 N 4 powder. The restriction of shrinkage seems to result from neck growth and strong aggregation among reacted Si 3 N 4 particles.

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