Excellent Dielectric Properties and Finite Element Simulation of Al-Epoxy Composites with Constructed Ultrathin Al₂O₃ Parallel-Plate Microcapacitors

Metal-polymer dielectric compositesshow promising potentialas embedded capacitors, whereas it remains a great challenge to achievea high dielectric constant (& epsilon;(r)) and low dielectricloss (tan & delta;) simultaneously. This work demonstrates a strategyfor overcoming this challenge. Al nanoparticles with self-passivatedultrathin Al2O3 shells are compacted under theuniaxial pressure (P), and Al-epoxy compositesare prepared by curing the liquid epoxy monomer that infiltrates intoAl compacts. The contacting regions between adjacent Al nanoparticlesare flattened and enlarged during the compacting process, so thatthe ultrathin Al2O3 parallel-plate microcapacitorsare constructed by the insulating Al2O3 shellsand conductive Al cores. The composite with P of100 MPa and Al volume fraction (& upsilon;(Al)) of 53.7% exhibitsthe & epsilon;(r) of 189 at 10 kHz, which is much higher thanthe & epsilon;(r) (48-102) of 0-3 type Al-polymercomposites with similar & upsilon;(Al) and even higher thanthe highest & epsilon;(r) (160) reported in the Al-polymercomposite with & upsilon;(Al) > 80%. Furthermore, the presentcomposites show low tan & delta; (<0.03) and good frequency andtemperature stability of & epsilon;(r). The finite element simulationproves that the construction and enlargement of ultrathin Al2O3 parallel-plate microcapacitors dramatically increasethe electric energy stored in Al2O3 and thereforegreatly improve the & epsilon;(r).