Electrical resistivity of silicon nitride-silicon carbide based ternary composites

New electrically conductive ternary composites were developed by adding 8 vol.% of ZrN or ZrB2 to a Si3N4-SiC matrix. During hot pressing, ZrB2 reacted with Si3N4 to form ZrSi2, ZrN, Si and BN whereas added ZrN did not undergo any reactions in the Si3N4-SiC-ZrN composite. The composites modified by ZrN or ZrB2 addition showed a lower resistivity (7 x 10(3) Omega cm and 3 x 10(-1) Omega cm) compared to the matrix (3 x 10(4) Omega cm). Further studies on the grain size distribution and the volume ratio of conducting and non-conducting phases excluded a percolation network of ZrN and ZrSi2 grains, in fact, doping of SiC grains and modified grain boundaries as a consequence of the formation of liquid phases during sintering are suggested to be the reason for the significantly lower resistivity of materials containing ZrSi2. A decrease in the composite resistivity due to a subsequent heat treatment was obtained for all hot-pressed composites. (C) 2011 Elsevier Ltd. All rights reserved.