A Comparative Study of Low Voltage SnO2- and ZnO- Based Varistor Properties

In the present work، the addition of CuO to the (Co، Cr، Nb) -doped SnO2 varistor systems for low voltage applications has been studied and compared with a typical ZnO-based formulation. The SEM micrographs exhibit a single phase microstructure having an average grain size of 10μm for SnO2- based varistors whereas the ZnO-based varistors show a multiphase structure with larger grains. The breakdown voltage، nonlinear coefficient، and leakage current are 0. 9kV/cm، 35، 7µA، respectively for the SnO2 based varistors which compare favorably with those of the low voltage ZnO-based varistors. A comparative study of the degradation phenomenon in the two systems indicates a superior behavior for the SnO2-based varistors.