VARISTORS PREPARED BY SELF-PROPAGATING COMBUSTION ZnO POWDERS

Using zinc nitrate, urea and additives as raw materials, doped ZnO nanopowders for varistors were prepared by the self-propagating combustion method. The powders were characterized by means of X-ray diffraction, scanning electron microscopy, specific surface area analysis and laser size analysis. The effects of addition amounts of urea on the properties of the powders and sintering temperature on the properties of ZnO varistors were studied. The mechanism of the reaction in the self-propagating combus- tion process was discussed. The results showed that doped ZnO powders prepared at 600 ℃ when the mass ratio of urea and metal salts is 1, possess good properties. A ZnO varistor with the best electronic properties was prepared by the powders, which had a po- tential gradient of 745.27 V/mm, a nonlinear coefficient of 56.53 and a leakage current of 6 μA.