Interfacial Polarization-Induced Loss Mechanisms in Polypropylene/BaTiO₃ Nanocomposite Dielectrics

Abstract

Polymer/inorganic particle nanocomposites (or nanodielectrics) have attracted pronounced attention for electric energy storage applications, based on a hypothesis that polymer nanodielectrics could combine the high permittivity of nanoparticles and the high electrical breakdown strength of the polymer matrix for enhanced dielectric performance. Although higher discharged energy densities have been reported for numerous polymer nanodielectrics, the dielectric loss mechanisms, which are extremely important for ultimate applications, are rarely discussed. In this work, we intend to address the intrinsic dielectric loss mechanisms associated with polymer nanodielectrics using a model system comprised of 70 nm BaTiO3 nanoparticles (BT NPs) in an isotactic polypropylene (PP) matrix. The effect of space charge-induced interfacial polarization on dielectric losses was investigated using bipolar and unipolar electric displacement -electric field (D-E) loop tests. Since the bipolar D-E loops always exhibited greater nonlinearity than the unipolar loops, the dielectric loss was attributed to the internal AC conduction loss from space charges (e.g., electrons) in the BT NPs, including boundary layer and bulk conductions. To mitigate the internal conduction along the PP/BT interface, atomic layer deposition of a nanolayer (5 nm) of amorphous TiO2 was applied to the BT NPs. Due to a higher resistivity, the coated amorphous TiO2 effectively reduced the boundary layer conduction loss. Nonetheless, the bulk conduction loss in BT NPs still needed to be reduced. This study suggests that more insulating high permittivity NPs are demanded for polymer nanodielectrics to enhance the dielectric performance.

Improved dielectric permittivity and retained low loss in layer-structured films via controlling interfaces

“…However, the dielectric permittivities of polymer dielectrics are usually very low (below 10 @1 kHz), which greatly hindered their wide applications. Toward this end, two strategies have been developed to improve the dielectric constants of polymer composites: (1) ceramic-polymer composites composed of high-k ceramic fillers (e.g., BaTiO 3 [23][24][25][26][27], TiO 2 [28,29], SrTiO 3 [30]) dispersed in polymer matrix and (2) conductor-polymer composites consisting of conductors (e.g., metals, [31,32], graphite [33,34], carbon nanotube [35][36][37], graphene [38,39], carbon black [40], and conductive polymer [41,42]) dispersed in polymer matrix. For ceramic-polymer composites, the enhancement of permittivity is limited (below 50 @10 kHz) even when the ceramic loading excesses 50 vol%, leading to deteriorated mechanical properties, high loss, and low breakdown strength [43].…”

Effects of internal and external electronic conduction in sodium titanate nanotubes on dielectric loss mechanisms in relaxor ferroelectric polymer nanocomposites

“…[24,33,34] Although enhanced apparent dielectric constants and increased discharge energy density are reported, the fundamental understanding of dielectric loss mechanisms in polymer nanodielectrics is just emerging. On the basis of a recent report, [35] dielectric losses of polymer nanodielectrics are closely related to the large contrast in permittivity and conductivity between the nanofillers and the polymer matrix. First, the high permittivity (ε r ) nanofillers tend to increase the local electric field in the polymer matrix, [36][37][38][39] especially between chained or clustered particles, [40] resulting in decreased electrical breakdown strength.…”

“…[42][43][44] To reduce the internal electronic conduction loss, unipolar, instead of bipolar, electric poling should be used. [35] Alternatively, highly insulating (conductivity σ <10 -13 S/m) nanoparticles with a high ε r (>100) should be used for polymer nanodielectrics; however, such nanoparticles are yet to be discovered. [35] In this study, we continue to investigate the effect of high aspect ratio nanofiber or nanotube fillers on the dielectric loss mechanisms in polymer nanodielectrics.…”

An ultra-broadband single-component fractional-order capacitor using MoS2-ferroelectric polymer composite

“…37-40 a) In this work, it is demonstrated that MoS 2 -PVDF ferroelectric polymer composites result in a broadband CPZ when they are used to fabricate FOCs. This broadband response results from the cumulative effect of three mechanisms on the composite's electrical properties: Maxwell-WagnerSillars relaxation, 41,42 the frequency-dependent phase angle of MoS 2 [due to its semiconducting nature 43 (see supplementary material Sec. S2, Figs.…”

“…Sillars relaxation takes place. 41 (2) Dipolar relaxation that takes place at intermediate frequencies due to the lack of the alignment response of the abundant dipoles in the polymer to the polarity change of the applied voltage. 5 Adding more fillers results in shifting of Maxwell-Wagner-Sillars relaxation towards higher frequencies [Figs.…”