Development of Reaction‐Bonded Electroconductive Silicon Nitride‐Titanium Nitride and Resistive Silicon Nitride‐Aluminum Oxide Composites

Abstract

Reaction‐bonded Si 3 N 4 · TiN and Si 3 N 4 · Al 2 O 3 composites were successfully fabricated by heating mixed powder compacts of Si and TiN or Si and Al 2 O 3 in a nitrogen atmosphere. The former showed electrical conductivity, owing to the presence of TiN. An electrical resistivity of 2.6 × 10 −5 Ω· m was obtained for the Si 3 N 4 · 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 Si 3 N 4 · Al 2 O 3 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 Si 3 N 4 · TiN/resistive Si 3 N 4 · Al 2 O 3 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 Al 2 O 3 . 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.