Potential-current characteristics in SiC/ZrB2 composite ceramics

ZrB2/SiC composite ceramics were fabricated to improve the electrical conductive properties of SiC matrix. The debinding and sintering temperatures were determined by computation of Gibbs free energy. As a result, all the samples have the relative density above 99%, and have excellent mechanical and electrical properties. The effects of ZrB2 content on the microstructure, mechanical and electrical properties were systematically studied. With increasing ZrB2 content, as-prepared composites show great improvement in their mechanical properties. Importantly, the introduction of ZrB2 weakened varistor nonlinear characteristic of composite and reduced its resistivity. The reason is the evolution of grain boundary in conductive paths. The sharp decrease of resistivity indicates the formation of percolation paths. The percolation threshold at 1 mA cm−2 obtained via percolation model is 10.7963 vol% (19.7098 wt%) ZrB2. This value is much less than conventional composites, because the percolation path originates from grain boundary breakdown other than continuous conductor chains.