Nanocomposite films with a small loading of two-dimensional Bi 2Te 3@Al 2O 3 hexagonal nanoplates exhibit a high dielectric constant of 140 and relatively low dielectric loss of 0.05 at 1 kHz.
Two-dimensional (2D) core–shell structure Bi 2Te 3@Al 2O 3 nanoplates were synthesized from 2D Bi 2Te 3 nanoplates via a sol–gel method, where the 2D Bi 2Te 3 nanoplates were prepared via a microwave-assisted method. Homogeneous nanocomposite films, with poly(vinylidene fluoride) (PVDF) as the polymeric matrix and Bi 2Te 3 nanoplates or core–shell structured Bi 2Te 3@Al 2O 3 nanoplates as the fillers, have been prepared. The dielectric behavior of the Bi 2Te 3/PVDF and Bi 2Te 3@Al 2O 3/PVDF nanocomposites has been investigated. Compared with the Bi 2Te 3/PVDF nanocomposite, the Bi 2Te 3@Al 2O 3/PVDF composite film exhibits larger breakdown strength and lower dielectric loss, due to the highly insulating Al 2O 3 shell layer, as well as the Al 2O 3 dielectric constant being incorporated into the Bi 2Te 3 nanoplate surface. As a result, the composite film loaded with 10 vol% 2D Bi 2Te 3@Al 2O 3 nanoplates exhibits a high dielectric constant of 140 and a relatively low dielectric loss of 0.05 at 1 kHz. Furthermore, finite element simulations were carried out to understand the dielectric mechanism of Al 2O 3 shell layer effects on the dielectric performances of the nanocomposite films. This study provides a solution for obtaining high- k dielectric composites with low dielectric loss, which is highly desired for power systems and advanced electronics.