Electrical Properties of ZnO Microvaristors under HV Application (特集放電現象・新素材とその応用技術)

概要

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Zinc oxide (ZnO) particles are well known for their non-linear properties. Recently, they are being used in epoxy resin of Air bushings to control the surface potential distribution. In this research work, we used 4 different types of ZnO particles (A, B, C and D) and measured their electrical characteristics. Among them, A and B were injected to epoxy resin. And the sample A was applied with high voltage (HV) application. Samples A, B and C were treated with heat for couple of hours before measurements. We have developed a measuring system by using a micromanipulator to measure the electrical properties of micro particles. The I-V and C-V characteristics of the samples were measured. We found non-linear properties in each particle while measuring I-V characteristics. Non-linearity appears for the DSB (Double Schottky Barrier) formed in grain boundaries. Microstructures of the samples were observed by a SEM. From their microstructures, it was confirmed that the I-V characteristics of ZnO particles depended only on the grain boundaries. We also calculated the donor concentration of ZnO and barrier height of DSB model from the C-V measurements. We found that the samples were not deteriorated either by HV application or the injection of them to epoxy resin.