Sintering Behaviour and Microstructure Development in Electroconductive Si3N4-TiN Composites

Abstract

The Si3N4-TiN composites offer the unique combination of thermal, mechanical and electroconductive properties making them suitable for wide range of engineering application. The use of the appropriate amount of TiN, which is dispersed in Si3N4 matrix, enables to achieve tailored electrical conductivity of composites, from high insulating to electroconductive ceramics. The use of TiN, ranging from 35 to 50%, together with appropriate sintering aids, resulted not only in fully dense compacts but also in compacts with a resistivity less than 10−1 Ωm as well. The addition of TiN has a marked effect in obtaining the uniform microstructure and improves also the mechanical properties such as the fracture toughness and flexural strength of composites as compared with those of the monolithic Si3N4 (Bellosi et al., 1992; Gogotsi, 1994; Boskovic et al., 1994; Choi et al, 1995). The electrical resistivity of Si3N4-TiN composites depends primarily on the amount of TiN content, but due to the percolation phenomenon and the probability of forming a conductive network, the conductivity depends in a great extent on the starting powders size and on the microstructure formed during the liquid phase sintering as stated by (1989), (1991) and (1991).