Model experiments describing the microcontact of ZnO varistors

Abstract

A macroscopic model of the microcontacts in ceramic ZnO varistors was prepared by using ZnO single-crystal plates and a layer of the usual oxide additives. The electrical properties of these model contacts are very similar to those of the microcontacts. Measurements on one-sided macrocontacts require the assumption of a ‘‘buried’’ potential barrier underneath the surface of the ZnO, the formation of which is explained by the distribution of the atomic defects and the dopants in the ZnO. Based on this idea, the I-V characteristics in the prebreakdown region and the breakdown voltage have been calculated.