The effect of SiO sub(2) on electrical properties of low-temperature-sintered ZnO-Bi sub(2)O sub(3)-TiO sub(2)-Co sub(2)O sub(3)-MnO sub(2)-based ceramics

ZnO-Bi sub(2)O sub(3)- TiO sub(2)-Co sub(2)O sub(3)-MnO sub(2)-based (ZBTCM) varistors were fabricated via the conventional solid-state method, and the effect of SiO sub(2) content on the phase transformation, microstructure, and electrical properties of the ZBTCM had been investigated. Results showed that this varistor can be sintered at a low temperature of 880 degree C with a high sintering density above 0.95 of the ZnO theoretical density. In these components, SiO sub(2) acts as a controller in ZnO grain growth, decreasing the grain size of ZnO from 3.67 to 1.92 mu m, which in turn results in an increase in breakdown voltage E sub(1mA) from 358.11 to 1080 V/mm. On the other hand, SiO sub(2) has a significant influence on the defect structure and component distribution at grain-boundary regions. When SiO sub(2) content increases from 0 to 4 wt%, the value of the interface state density (N sub(s)) increases sharply. At the same time, the electrical properties are improved gradually, and reach an optimized value with the nonlinear coefficient ( alpha ) up to 54.18, the barrier height ( sub(b)) up to 2.90 eV, and the leakage current (I sub(L)) down to 0.193 mu A/cm super(2).