Abstract
Reaction-bonded Si3N4· TiN and Si3N4· Al2O3 composites were successfully fabricated by heating mixed powder compacts of Si and TiN or Si and Al2O3 in a nitrogen atmosphere. The former showed electrical conductivity, owing to the presence of TiN. An electrical resistivity of 2.6 × 10−5Ω· m was obtained for the Si3N4· TiN composite with 70 vol% TiN. The composite with 20 vol% TiN showed an electrical resistivity of 0.22 Ω· m and a bending strength of 460 MPa. On the other hand, the Si3N4· Al2O3 composite had insulating properties. The use of an appropriate amount of resin binder resulted in a higher green density and, consequently, a higher bending strength. Moreover, electroconductive Si3N4· TiN/resistive Si3N4· Al2O3 complex ceramics could be fabricated by heating green compacts composed of two different portions, one composed of mixed powders of Si and TiN and the other of Si and Al2O3. Attainment of such complex ceramics was attributed to the small dimensional change at the nitriding stage, under 0.3% and the similarity of the thermal expansion coefficients of the two composites.
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