Application of Zinc Oxide Varistors

TLDR

ZnO varistors have been underexplored in systematic literature, prompting this study of their applications. The paper aims to detail the application parameters of ZnO varistors and their link to microstructure and processing. It reviews the varistor’s electrical, physical, chemical, and microstructural fundamentals, uses these to define nonlinear I‑V application parameters, and examines how microstructure and processing affect them, concluding with a grain‑boundary defect model for reliability. The grain‑boundary defect model explains both the instability and stability of ZnO varistors during use.

Abstract

This paper deals with the application of ZnO varistors—an area which has not been treated in a systematic way in the literature. The paper starts with a brief description of the fundamental properties comprising the electrical behavior as well as the physics, chemistry, and microstructure of the varistor. These properties then form the basis for defining the application parameters that are directly related to the nonlinear current‐voltage characteristics of the varistor. This paper provides a detailed description of these parameters and their relation to microstructure and the processing of the varistor. Finally, a discussion is presented on the reliability of the varistor by considering a grain‐boundary defect model which explains both the instability and the stability under use conditions.