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

Metal-polymer dielectric composites show promising potential as embedded capacitors, whereas it remains a great challenge to achieve a high dielectric constant (ε) and low dielectric loss (tan δ) simultaneously. This work demonstrates a strategy for overcoming this challenge. Al nanoparticles with self-passivated ultrathin AlO shells are compacted under the uniaxial pressure (), and Al-epoxy composites are prepared by curing the liquid epoxy monomer that infiltrates into Al compacts. The contacting regions between adjacent Al nanoparticles are flattened and enlarged during the compacting process, so that the ultrathin AlO parallel-plate microcapacitors are constructed by the insulating AlO shells and conductive Al cores. The composite with of 100 MPa and Al volume fraction (υ) of 53.7% exhibits the ε of 189 at 10 kHz, which is much higher than the ε (48-102) of 0-3 type Al-polymer composites with similar υ and even higher than the highest ε (160) reported in the Al-polymer composite with υ > 80%. Furthermore, the present composites show low tan δ (<0.03) and good frequency and temperature stability of ε. The finite element simulation proves that the construction and enlargement of ultrathin AlO parallel-plate microcapacitors dramatically increase the electric energy stored in AlO and therefore greatly improve the ε.