Application of Direct Current and Temperature Stresses of Low-Voltage ZnO Based Varistor Ceramics

Problem statement: The stresses to humidity, DC and AC bias, multiple impulse voltages and high temperatures are known to affect the varistor performance and it is also interesting to know the effect of both DC bias and temperature stresses at the same time. Approach: Here, the simultaneous DC and temperature stresses degradation was investigated to see the changes of nonlinear coefficient (α) in Zn-Bi-Ti oxide low-voltage varistor ceramics sintered at various sintering temperatures (1140-1260°C) and two sintering duration times of 45 and 90 min. The current-voltage characteristics of the varistor ceramics were evaluated. Results: The α of ceramic was observed to be decreased with increasing sintering temperature. After loaded with DC and temperature stresses of 0.75V_1mA/80°C/12 h, the α of ceramics for 90 min sintering time decreases with sintering temperature, however that sintered for 45 min sintering time increase with sintering time. Conclusion: The application of DC and temperature stresses in Zn-Bi-Ti oxide ceramics sintered at very long time cause the α to decrease as evidence from higher leakage current.