TRANSIENT CONDUCTION PHENOMENA IN NON-OHMIC ZINC-OXIDE CERAMICS

Transient conduction phenomena in non-Ohmic ZnO ceramics are studied. Several characteristic phenomena are observed by applying a rectangular-wave- pulse voltage, such as the gradual increase of current, the voltage overshoot, the current overshoot, and the current oscillation. In order to clarify these phenomena, the experiments of the effect of additives, the temperature dependence, and the effect of preinjection of carriers have been carried out. These phenomena of gradual increase of current and voltage overshoot, current overshoot, and current oscillation can be reasonably explained by the electron trapping in the intergranular layer, by the delay in the formation of conduction electrons, and by the generation of the group of excess electrons in the intergranular layer, respectively.