Scalable Preparation of Fully Coated Ag@BaTiO₃ Core@Shell Particles via Poly(vinylpyrrolidone) Assistance for High-k Applications

Abstract

This paper reports a poly­(vinylpyrrolidone) (PVP)-assisted synthesis of Ag@BaTiO3 (BT) core@shell particles, consisting of smooth and fully coated BT shells on Ag cores. PVP adheres to Ag by coordination attraction, and it is present as a framework on the Ag surface. Driven by the adhesion forces from PVP, fully coated BT shells form on the template of the PVP framework. The shell phase is formed through a modified low-temperature direct synthesis method. Scanning electron microscopy examination of morphological evolution reveals smooth surfaces of the oxide coatings on Ag cores. X-ray diffraction pattern, energy-dispersive X-ray spectra, line scan, and mapping confirm the phase, chemical composition, and configuration of the shells. The synthesis method in this paper can achieve controllability of the growth rate and shell thickness. Because of the fully coated shells of BT, the poly­(dimethylsiloxane) composites filled with synthesized core@shell fillers have very small leakage currents of ∼10–8–10–7 A/cm2. A high permittivity of 202 (εr/εm = 84) and a low dielectric loss of 0.003 are achieved at 1 MHz in composites filled with 40 vol % Ag@BT fillers. Lichtenecker’s theory containing the equivalent permittivity of core@shell Ag@BT originating from interfacial polarization is used to account for the dielectric constant of the composite. The smooth and fully coated Ag@BT core@shell particles can be used in composite materials for high-dielectric-constant and low-loss applications.

Poly(vinylidene fluoride-co-hexafluoropropylene)-MXene Nanosheet Composites for Microcapacitors

“…On the basis of the percolation theory, a higher dielectric constant can more easily be achieved with lower filler content by replacing ceramic fillers with conductive fillers. − There is an abrupt increase when the content of conductive fillers is close to the percolation threshold that depends on the size, shape, and spatial arrangement of conductive fillers. , The percolation threshold can be very low for conductive fillers with a high aspect ratio. For example, two-dimensional (2D) fillers (e.g., graphene nanosheets − ) with higher aspect ratio have lower percolation threshold than one-dimensional (1D) fillers (e.g., nanowires, nanofibers, and nanotubes − ) and zero-dimensional (0D) fillers (e.g., metal nanoparticles , ). Usually, two-phase composites have a value of no more than 16 vol% for the percolation threshold .…”

“…10,11 The percolation threshold can be very low for conductive fillers with a high aspect ratio. For example, two-dimensional (2D) fillers (e.g., graphene nanosheets 12−16 ) with higher aspect ratio have lower percolation threshold than one-dimensional (1D) fillers (e.g., nanowires, nanofibers, and nanotubes 17−21 ) and zero-dimensional (0D) fillers (e.g., metal nanoparticles 22,23 ).…”

Synergistic enhancement in mechanical, thermal, and dielectric properties of PANI@BT/PVDF composites by adding 2D nanoplatelets

“…20 Fabrication of core-shell structure hybrid fillers is beneficial to combining the complementary functionalities of ceramics and conductive fillers. [21][22][23] Moreover, multiple interfaces provide more probability for the interfacial polarization. 24 Compared with metal shell and inorganic shell, conductive polymer shell presents more moderate electronic conductivity and better compatibility with polymer matrix, which helps to the dispersion of fillers in polymer matrix.…”

“…Fabrication of core‐shell structure hybrid fillers is beneficial to combining the complementary functionalities of ceramics and conductive fillers 21–23 . Moreover, multiple interfaces provide more probability for the interfacial polarization 24 .…”

Improving the Performance of Dielectric Nanocomposites by Utilizing Highly Conductive Rigid Core and Extremely Low Loss Shell

“…Another widely used strategy is to prepare polymer dielectric nanocomposites by incorporating conductive nanoparticles into the polymer matrix, such as metal nanoparticles, − carbon nanotubes (CNTs), − graphene, − graphene oxide (GO), , and carbon black, , which can achieve a high dielectric constant at a very low nanoparticle content. However, due to the existence of the percolation phenomenon, the dramatic enhancement of the dielectric constant near the percolation threshold ( f c ) is often accompanied by a sharp increase in the dielectric loss due to the formation of the conductive path in the nanocomposites.…”