Construction of parallel-structured composites based on a theoretical model to achieve an ultra-high dielectric constant†

Abstract

According to theoretical studies on ceramic/polymer composite dielectrics, the maximum achievable dielectric constant is observed in composites with a parallel structure connecting the ceramic and polymer phases. However, the practical preparation of parallel-structured composites poses significant challenges. Here, aimed at the theoretical model, we prepared a parallel-structured BaTiO₃ (BT) skeleton through bidirectional freezing, and further prepared a parallel-structured BaTiO₃/epoxy (BT/EP) composite through vacuum impregnation. When the electric field is completely parallel to the interfaces between BT and EP phases, the composites basically realize the ideal parallel structure and exhibit excellent dielectric properties. For example, the composite with 59 vol% BT content has an ultra-high dielectric constant of 2017 and shows a low loss of <0.02 at 1 kHz. Even at a low BT content of 18 vol%, the dielectric constant of the parallel-structured composite is still as high as 489 at 1 kHz. Based on the ultra-high dielectric constant of the parallel-structured composites, a high polarization intensity of 24.8 μC cm⁻² and a discharge energy density of 13.4 × 10⁻² J cm⁻³ are achieved at a low electric field of 4 kV mm⁻¹. Experiments and simulations demonstrated that the parallel arrangement along the direction of the electric field and the connectivity of the ceramic fillers are the key factors to realize the parallel structure. This work achieved the parallel structure described by the theoretical model and further clarified the relationship between the structure and dielectric properties of the composites.