Thickness effect on threshold electric field of ZnO microvaristors/silicone rubber composite with nonlinear conductivity

Abstract

As a functional material, ZnO microvaristors/silicone rubber composite, with nonlinear conductivity, will be manufactured to different thicknesses for different applications. However, few study focuses on the thickness effect of the composite. In this paper, ZnO/SiR composites with thickness from 50 μm to 2800 μm were prepared. The conductivity results show that the threshold electric field (Eb) of the composites increases from 40 V/mm to a stable value (more than 1000 V/mm) as the thickness increases. A simulation model based on the Voronoi network was carried out to explore the mechanism. For the thickness close to the diameter of fillers, the key element determining Eb is the microstructural nonuniformity of electrical characteristics of microvaristors. As the sample becomes thick, the increasingly tortuous conduction path is considered to trigger off the increase of Eb. The thickness effect discussed in this paper will be helpful in designing electrostatic discharge elements in electronic devices.