Research on the Dielectric Property of Sandwich-Structured Polymer Coated with Hexagonal Boron Nitride Layers

Polymer dielectrics are widely used in electric power systems and electronics due to their high energy density. In this work, two types of polymer dielectrics, polythiourea (PTU) and polyurea (PU), are selected as the substrate and spatter with the wide bandgap hexagonal boron nitride (h-BN) on both sides in different times. For PU, a wider bandgap allows PU has higher breakdown endurance compared to PTU. The influence of different spattering time on the dielectric properties of the composite films are studied. After spattering, the breakdown strength of the composite films has effective improvements. As the spattering time increases, the content of h-BN on the composite films shows an exponential growth trend. For PTU, it can be observed that the breakdown strength of modified PTU shows increasing first and then decreasing after spattering the h-BN. The spattering time is 10 minutes, the breakdown strength reaches the maximum value, having an increase of 24.3%. The sandwich composite structure coated with wide bandgap proposed in this work provides a new strategy for optimizing the energy storage characteristics of dielectric polymer films.