Highly enhanced frequency- and temperature-stability permittivity of three-phase poly(vinylidene-fluoride) nanocomposites with retaining low loss tangent and high permittivity

Abstract

Although ceramic/polymer composites have been of great interest as embedded capacitor materials, the composites have a low dielectric permittivity (ε′ ≪ 100) and very large dissipation factor (tanδ ≫ 0.1). In this work, the hybrid particles of silver nanoparticles deposited on BaTiO3 nanoparticles (nAg-nBT) have been used as a filler to enhance the ε′ response in a poly(vinylidene-fluoride) (PVDF) polymer with retaining low tanδ. Residual isolated particles of nAg (i-nAg) and nBT (i-nBT) are the key factors for enhancing the dielectric properties. Significantly increased ε′ ~ 247 (at 103 Hz) with tanδ ~ 0.038 is obtained. The ε′ value is slightly dependent on frequency and temperature over wide ranges. A linear increase in ε′ of the composites at low volume fractions of filler (fAg+nBT < 0.29) is caused by a high ε′ value of nBT particles. An abrupt change in ε′ is observed in the composites at fnAg+nBT > 0.29, which is attributed to a shorten interparticle distance between filler particles, giving rise to strong interfacial polarization. The dielectric behavior can be well described by the effective medium percolation theory (EMPT) model. The discrete deposition of nAg observed in the nAg-nBT and uniform distribution of i-nAg in the PVDF matrix, which is dispersed by nAg-nBT and i-nBT particles, can effectively prevent the formation of the conduction pathways. The obtained low tanδ over the temperature range of 30-140 °C is explained by these two reasons. This research provides a new important concept for the material development of dielectric polymer matrix composites..