Electroconductive ceramic composites with low-to-zero shrinkage during sintering

Dense low or even zero shrinkage TiN/Si3N4 and ZrN/Si3N4 composites have been obtained by reaction of transition metal silicides TiSi2, ZrSi2 and Ti5Si3 with nitrogen gas in the temperature range 700–1500 °C. After transformation to nitrides, densification of the reaction-bonded composites is achieved (95–97% TD) in a subsequent sintering step up to 1800 °C in flowing nitrogen. Since the nitridation reaction is accompanied by volume expansions, linear shrinkage of the sinter bodies in relation to the die-pressed powder compacts is very low. In the case of TiSi2 even zero shrinkage was achieved by adjusting the green density during axial compaction by variation of the applied stress. The electrical conductivities of the obtained ceramic specimen differ strongly due to the volume amounts of the conducting phases and different microstructures. The conductivity of the composites made from pure silicides or their mixtures ranges from 10−1 to 105 Ω−1 cm−1.