Analysis of ZnO varistors prepared from high-energy mechanical activation

ZnO varistors were prepared by high-energy mechanical activation to study its effect on the microstructure and electrical properties. Comparison of different permutation and combination of ZnO powders and additives subjected to activation for 0, 6 and 12 h were given in I-V, C-V, complex resistance study. The variation of Schottky barrier height phi(b), donor concentration N-d, interface state density N-t and depletion layer width G were calculated in different samples. Finally, individual grain boundaries were investigated by SSPM (Scanning Surface Potential Microscopy) under in situ applied fields, allowing determination of the voltage dependence of grain boundary electronic properties.