Influence of Adding SiC on Microstructure and Electrical Properties of ZnO-based Nanocomposite Varistor

In this research the influence of adding SiC on microstructure and electrical properties of ZnO-based Nanocomposite varistors were investigated. SiC was added with amounts of 10-0 mass% to ZnO-based varistor composition. It is found that SiC allows reaching to high threshold voltage with formation of fine-grained ZnO.Another important effect of adding SiC is formation Zn2SiO4 (Willemite) on the surface of SiC grains. With this effects SiC had great influence on Varistor electrical properties. On the other hand relative density decreased with increasing percentage of SiC in the composition. Hence with adding SiC to the composition, the threshold voltage of varistors (VT) and non-linear coefficient (α) increased at first and then decreased with increaseing of porosity. Also Current leakage decreased at first and then increased with adding more SiC. Also ZnO powder size effect on the final properties was examined in this reasearch by using submicron size and Nano size ZnO powder. The best achieved electrical result was threshold voltage as large as 4220 V/cm and nonlinear coefficient α=44 that were gained by using of Nano ZnO powder and adding %4 SiC to the composition.