Investigation Of Properties And Microstrcture Of Nanometer ZnO Varistors

In the paper, the main work is to improve the microstructure uniformity and electric property of the ZnO varistor ceramic. On the basis of analyzing the ZnO varistor microstructure and crystal characterization, the nanometer ZnO varistor is got by means of several additives together. The electric properties and the relations between microstructure and property of the nanometer ZnO varistor and micrometer ZnO varistor are investigated through different ways. At last, the main conclusions are as follows:(1) Through optimizing the process craft, the nanometer ZnO varistor has more uniform composition, narrower the partical size distribution, and the powder grain aveage size is 38.4nm. Comparing with micrometer ZnO varistor, the nanometer ZnO varistor powder has a bigger surface area (171m2/g), which is about 16.1 times of that of micrometer varistor powder.(2) Nanometer ZnO varistor ceramic is mainly composed of ZnO main grain phase, Bi2O3 rich bismuth phase and spinel phase which consists of Zn7Sb2O12 and Zn2TiO4 etc.. The shape ofgrain boundary phase is similar to equilateral triangle in the triple point of ZnO grains, the grain boundary of two crystalline grain intersection points are straight, compact and clean, and there is not air vent and impurity, so the microstructure of the nanometer ZnO varistor ceramic is close to that of the ideal ceramic.(3) Under the same fabrication craft, the unite thickness varistor voltage V/mm of nanometer ZnO varistor ceramic is 456V, and that of micrometer ZnO varistor ceramic is 247V. If under the conditions of the same voltage, nanometer materials appear to be better in saving raw materials and can produce more obvious economic benefits compared with micrometer materials.(4) Compared the nonlinear coefficient, the leakage current and the varistor voltage to sinterring temperature, respectively, the nonlinear charactristics of nanometer ZnO varistor ceramic are better than those of micrometer ZnO varistor ceramic, and the best sintering temperature of nanometer ZnO varistor ceramic(1150°C) is lower than that of micrometer ZnO varistor ceramic (1200 °C).