Electric Field Induced $\text{ZnO}/\mathrm{A}1_{2}\mathrm{O}_{3}$ Self-Assembly Modulates the Nonlinear Conductivity of Composites

Nonlinear electrically conductive composites are widely used for electric field grading in HVDC systems. However, composites prepared using current methods can rarely simultaneously meet the requirements of a high nonlinear coefficient, low switching field and low filler content, which limits their application scope. In this study, we performed the Monte Carlo simulation for the self-assembly of the binary particles in an electric field. The assembly form shifts from string to column as the electric field increases. In the column, the fillers are assembled according to the body-centered tetragonal (bet) structure, which increases the number of contact points. Finite element simulations reveal that the composites with 4 vol% loading of self-assembled ZnO microvaristor can obtain nonlinear conductivity properties similar to those of ZnO microvaristor. When replacing some of the ZnO microvaristor with $\mathrm{A}1_{2}\mathrm{O}_{3}$ microspheres, the switching electric field strength can be modulated (from 250 to 1700 V/mm) while maintaining a high nonlinear coefficient (up to 60) to suit different insulation scenarios. This paper proposed the method on modulating the nonlinear conductivity of composite materials based on binary particles $(\text{ZnO}/\mathrm{A}1_{2}\mathrm{O}_{3})$ assembly induced by the electric field.