The invention concerns novel varistors based on
zinc oxide and a method for making same, which consists in using as base products nanocrystalline powders obtained by high-intensity mechanical
grinding and in subjecting the mixture resulting from said nanocrystalline powders a consolidating treatment such as
sintering, in suitably selected temperature and time conditions so as to retain the smallest possible grain size of ZnO. The resulting varistors have a very fine
homogeneous microstructure and an average grain size characteristically not more than 3pm, i.e. five times smaller than standard materials. Said novel varistors have a larger number of grain boundaries per unit length unit and therefore a much higher
breakdown voltage. Said
voltage is characteristically higher than 10 kV / cm and can reach 17 kV / cm which is almost one
order of magnitude above the
breakdown voltage of standard varistors. The non-
linearity coefficient of the current-
voltage curve is also improved, and is greater than 20 and can reach values as high as 60. Moreover, the leakage currents below the
breakdown voltage of said varistors, are much lower.