A modified measurement method of electrical properties for ZnO microvaristors by direct measurements

Zinc oxide (ZnO) materials are fine ceramics with non-linear electrical properties. Their non-linear electrical properties appear from a double Schottky barrier formed in the grain boundaries (GBs). These microparticles are not easy to measure directly with electrical microprobes due to their small size (i.e., 50–100 µm). We developed a direct measurement process with two Cu cables of small diameter. In this paper, we have developed an amplified method of the previous measurement system, which can measure not only one ZnO microvaristor directly but also a group of microvaristors in a series connection. The I–V characteristics of the microvaristors were measured with the modified method, and we found non-linear properties in each particle while measuring I–V characteristics. Their fine structures were also investigated, and the non-linear I–V characteristics showed a direct relationship with the number of the GBs of the samples. Moreover, varistor voltage was calculated for a single GB for the I–V measurements for ZnO microvaristors connected in a series connection.