Improvement Of ZnO Varistor Performance

The composited nanometer additives of ZnO varistor were prepared by the Sol-Gel method through lots of experiments on the basis of analyzing the theory of the Sol-Gel method in this dissertation. The diversified phenomenon in the experiment was also described and discussed in details.The powders of ZnO varistor fabricated by blending and grinding of ZnO, Sb₂O₃, SiO₂ and multiplex composite nanometer additives prepared by the Sol-Gel method were used to manufacture varistors with the size of 8.5mm in diameter and 1mm in thickness under proper technique. The microstructure of the varistor was analyzed by SEM and the performances of ZnO varistor were also tested. The results show that the Sol-Gel powder is homogeneous in distribution of dopants, the grains are regular and small in size and the pores are fewer in quantity. The varistors made by the Sol-Gel method show great improvement relative to conventional technique in the electrical properties. The 8/20μs surge absorption capability attains to 2500A and the withstanding rectangular current pulse(2ms) capability preponderates over 46J. Simultaneity, the small electrical current character was improved obviously.The effect of the different sintering temperature on the electrical performances of ZnO varistor was researched. The conclusion is drawn that 1100℃is the appropriate temperature of sintering. The effect of the electrical ageing technology on the 2ms rectangular current pulse capability of ZnO varistor was also studied. It is discovered that the current pulse capability of the varistor improved under the condition of Impulse voltage is 2.5 times of the varistor voltage and the times of the impulse is 6.