Energy Dispersive Spectrometer Analysis of AC Aged Zinc-Oxide Varistors

Aging performance decides the long-term stable operation of ZnO varistors. This paper applied the Scanning Electron Microscope (SEM) to determine the elements distribution inside ZnO varistors before and after ac aging, based on the Energy Dispersive Spectrometer (EDS) analysis, which consists of point analysis, line scan analysis, and mapping analysis. From experimental results, we can conclude that the combination of mapping analysis and line scan analysis can provide a relatively accurate elements distribution. The line scan analysis on ZnO varistors after aging shows that the distribution of zinc changes a lot along grain boundaries in ZnO varistors after aging test, and zinc accumulates along the boundary, which accounts for the migration of zinc ions. This result can provide fundament to determine the aging mechanism of ZnO varistors.