Residual voltage caused by grain boundary in ZnO varistor ceramics

The residual voltage of ZnO varistor ceramics is not only determined by grain resistance but also by the process of grain boundary breakdown. Al-doped ZnO varistor ceramics were prepared on the basis of traditional composition by the solid stated method. The current-voltage characteristics (I-V), dielectric spectroscopy of the samples were measured and the grain boundary micro-parameters were calculated, including the height and width of the Schottky barrier, the carrier concentration and so on. It was indicated that the barrier height plays a major role in determining grain boundary residual voltage. From this point, the grain boundary residual voltage can be decreased by controlling the grain boundary barrier through adjusting the concentration of intrinsic defects with doping method.