Tailoring energy storage properties of epoxy composites using ferroelectric, anti-ferroelectric particles and hybrid ceramic fillers

Epoxy-based dielectric composites reinforced with ferroelectric BaTiO3 and antiferroelectric AgNbO3 were fabricated and comprehensively evaluated to investigate the influence of filler type and composition on dielectric and energy storage performance. Structural, spectroscopic and microstructural analyses confirmed the successful incorporation of the ceramic fillers within the epoxy matrix. BaTiO3/epoxy composites exhibited markedly enhanced dielectric permittivity and polarization, resulting in a maximum recoverable energy density of 134.4 mJ·cm‒3, albeit with moderate charge-discharge efficiency due to hysteresis-induced energy loss. In contrast, AgNbO3/epoxy composites displayed lower permittivity but significantly reduced dielectric loss and excellent efficiency, reaching up to 96.7%, owing to low remanent polarization and a highly reversible dielectric response. Building on these complementary characteristics, hybrid BaTiO3-AgNbO3/epoxy composites were developed and found to provide complementary improvements in dielectric and energy-storage performance. The optimal hybrid formulation (15 wt% BaTiO3/30 wt% AgNbO3) achieved the highest recoverable energy density of 155.8 mJ·cm‒3, while the equimolar hybrid (22.5/22.5) provided exceptional efficiency of 99.06% with minimal energy loss. These enhancements arise from the complementary dielectric responses of the two ceramic fillers together with polymer-ceramic interfacial effects. The results demonstrate that combining ferroelectric and antiferroelectric fillers offers a powerful strategy for tailoring the dielectric response and optimizing energy storage performance in polymer-based composites.