Suppressed dielectric loss and enhanced breakdown strength in Ni/PVDF composites through constructing Al2O3 shell as an interlayer

Developing polymer dielectrics with a low dielectric loss but high dielectric permittivity ( ε ′) and breakdown strength ( E b ) is constantly pursued for applications in microelectronics and electrical industries. In this work, nickel (Ni) powders were coated by a layer of insulating aluminum oxide (Al 2 O 3 ) via a facile sol–gel process, and the obtained core–shell Ni@Al 2 O 3 particles were admixed into poly(vinylidene fluoride) (PVDF) to study the impacts of the Al 2 O 3 shell and its thickness on dielectric properties of the composites. The results verify the formation of the insulating Al 2 O 3 layer on the surface of the Ni core, which obviously enhances interfacial compatibility and interactions between the matrix and the fillers. The Ni@Al 2 O 3 /PVDF composites show better dielectric performances compared with the pristine Ni/PVDF. The dramatically suppressed dielectric loss and conductivity can be attributed to the insulating Al 2 O 3 interlayer avoiding the Ni cores from direct contact with each other and blocking the long-range migration of electrons. Furthermore, the Al 2 O 3 shell serves as an interlayer which lessens the distortion and concentration of local electric field subsequently leading to enhanced E b . Thus, the dielectric properties of the Ni@Al 2 O 3 /PVDF composites can be effectively tuned through finely tailoring the Al 2 O 3 shell’s thickness. The developed Ni@Al 2 O 3 /PVDF composites with high E b and ε ′ but low dielectric loss have potential applications in the microelectronic and electrical industries.