Synergistically modulating multiscale polarizations in Al@Al2O3@TiO2/PVDF composites towards elevated integrating dielectric properties

Against the backdrop of the booming sophisticated electronics industry, polymer composites integrating superior dielectric permittivity ( ε ), low loss (tan δ ) and excellent breakdown strength ( E b ) have become a persistent pursuit in the research community. To simultaneously bolster the ε and E b in alumina (Al)/polyvinylidene fluoride (PVDF), in this study the neat Al particles were first surface-oxidized to thicken the alumina (Al 2 O 3 ) thickness and then encapsulated with a titanium dioxide (TiO 2 ) layer, followed by an investigation into the dielectric properties of the resulting Al@Al 2 O 3 @TiO 2 /PVDF composites. The results indicate that the Al@Al 2 O 3 @TiO 2 /PVDF exhibits a higher ε and E b but lower tan δ relative to pristine Al/PVDF. The elevated ε stems from the synergistic regulation of high-frequency fast intra-particle and low-frequency slow inter-particle polarizations in Al@Al 2 O 3 @TiO 2 /PVDF. The Al 2 O 3 @TiO 2 double-shell not only prevents direct contact between conductive Al but also induces deep traps immobilizing charges and lifts the energy barrier for captured charges de-trapping, thus restraining the tan δ and leakage current. Moreover, the double-shell effectively strengthens interfacial interactions and alleviates strong dielectric mismatch between the two components, leading to much reduced electric tree growth and improved E b . Theoretical simulation further reveals a profound understanding of the inherent multiple polarization mechanisms and the charge migration modulation induced by the double-shell structure. So, this work provides unique insights for realizing simultaneously high ε , superior E b and minimal tan δ via core@double-shell structure in percolating composites, which cannot be achieved in traditional composites, offering considerable application potential in power equipment and electric devices.