Correlation between sintering temperature and electrical properties of ZnO-polyanilinepolyethylene composite varistors

Varistors were prepared by using hot press method at the sintering pressure of 60 MPa and different sintering temperature of 70 °C, 90 °C, 110 °C and 130 °C. Samples with the following specific mass percentage values were prepared: 92% wt. ZnO- 4% wt. PANI- 4% wt. PE. The effect of sintering temperature on their electrophysical behavior were then investigated. Current-voltage characteristic of the samples reveals that leakage current increases with increasing sintering temperature. Furthermore, increasing sintering temperature results in reduction of breakdown voltage, nonlinear coefficient, potential barrier height and electrical resistance in pre-breakdown region. Results are analyzed regarding SEM micrographs of the samples. In these varistors, grains and their boundaries are mainly formed from zinc oxide and polymeric materials, respectively. Regarding to SEM micrographs, the increase of sintering temperature leads to decrease of inter-grain spacing. Thus, potential barrier height between boundaries decreases and leakage current increases.