Enabling high dielectric constant and low loss tangent in BaTiO3–epoxy composites through a 3D interconnected network structure of ceramic phase

Abstract

Constructing ceramic–polymer composites with a 3–3 connectivity is an effective strategy to achieve a notable increase in the dielectric constant at low ceramic contents. However, the dielectric data of the 3–3 composites with a low ceramic content (<10 vol. %) are still limited, and further investigation is thus required. Herein, composites with a 3–3 connectivity, in which BaTiO3 (BTO) and epoxy are self-connected in three dimensions, were developed and constructed at low BTO contents (2.0–8.3 vol. %). A three-dimensional network structure of the BTO ceramic (3D-BTO) was constructed via the sacrificial template method using polyurethane foam as the template. The dielectric constant and loss tangent of the composites increased with increasing BTO content. At a BTO content of 8.3 vol. %, the dielectric constant of the composite considerably increased to 33.4 at 1 kHz, which was ∼10-fold higher than that of neat epoxy (3.5). The loss tangent had a low value of< 0.030. By comparing with several theoretical models, the dielectric constants of the composites were well fitted with the effective medium theory model at low fitting factors (n = 0.008–0.013). The considerable increase in the dielectric constant of the composites with a low loss tangent at a low BTO content was attributed to the strong interfacial polarization and continuous polarization pathways through the interconnected 3D-BTO network structure in the composites. This study fills the gap in the literature by providing missing data on the dielectric properties of 3–3 composites at low ceramic contents (<10 vol. %), as well as a theoretical prediction.