Significantly enhanced permittivity and energy density in dielectric composites with aligned BaTiO3 lamellar structures
Significant improvement of the permittivity and energy density will enable the miniaturization of dielectric capacitors and promote the integration for applications in electrical power and defense systems. In this work, lamellar composite architectures formed from aligned barium titanate (BaTiO3) in an epoxy resin are fabricated using the freeze casting method. Due to the continuous coupling effect originated from the interconnected and highly oriented BaTiO3 particles, this composite exhibits extremely high permittivity (εr = 1408) at 1 kHz, which is the highest value achieved in BaTiO3/polymer composites reported so far and fits well to the parallel mode of the mixing rule. A finite element model is used to investigate the local electric field distributions in the BaTiO3 laminar under the applied electric field parallel and perpendicular to the freezing direction, respectively. A high ratio value of discharge energy density per electric field, Udis/E, ~ 0.033, is achieved due to the high electric displacement of D = 15.11 µC/cm2 and discharge energy density of Udis = 19.6×10-2 J/cm3 achieved at a low electric field (6 kV/mm). This work provides an effective strategy of designing ceramic-polymer composite to realize high permittivity and energy density of capacitors for modern electrical and electronic industries.