Field Grading Composites Tailored by Electrophoresis—Part 2: Permittivity Gradient in Non-Uniform Electric Field

A series of three articles present an innovative way to build advanced functionally graded materials (FGM) based on polymer/ceramic composites tailored by electrophoresis from the process principle to their field grading application in power electronics. In this Part 2, it was studied the impact of a non-uniform electric field on the high-k SrTiO3 particle organization within an epoxy matrix. In that purpose, DBC substrates with sharp metallization tracks were used to generate a strong electric field divergence. This non-uniform field has been used to organize the particles around the field reinforcement regions during the electrophoresis process. It was discovered that the particles self-arrange into a conformal composite FGM layer that presents a local permittivity gradient: the highest ε being located around the electric field peak areas. This new process could be used to selectively `heal' the electric field-induced weaknesses of any high voltage electrical system by using its own design.