Dielectric Relaxation Strength Research Articles

Moderate electric field driven ultrahigh energy density in BiFeO3–BaTiO3–based ceramics with improved relaxor behavior and breakdown strength

Dielectric ceramic–based capacitors have triggered growing concerns because of their potential applications in next–generation pulsed power electronic devices. However, the low energy density seriously hampers their further development, and the high energy density (>6 J/cm3) is generally realized under a giant external electric field (>500 kV/cm). Herein, an ultrahigh recoverable energy density of 8.5 J/cm3 and a high efficiency of 87 % under a moderate electric field of 470 kV/cm is obtained in the Sr(Sc1/2Nb1/2)O3 modified BiFeO3–BaTiO3 ceramics via the improved dielectric relaxation and electric breakdown strength (Eb). And the promoted band gap and reduced grain size play a key role in enhancing Eb. Moreover, the sample with the optimal composition also exhibits superb thermal reliability at a wide temperature range, and outstanding frequency and cycling stability under 350 kV/cm. This work not only provides a hopeful alternative for advanced energy storage capacitors, but also demonstrates an effective way to explore high–performance dielectric materials.

Effects of cross‐linked networks on dielectric properties of epoxy resins based on molecular dynamics

AbstractIn this paper, three epoxy resin systems commonly used in power equipment are prepared to obtain cross‐linked networks with structural differences. The relationship between microscopic structures and dielectric properties of epoxy resins is investigated and discussed. Experimental results show that the polarization and conductance losses are inhibited in the anhydride‐cured systems with methyl groups. The molecular dynamics (MD) simulation shows that rigid anhydride structures (such as methyl groups) play a major role in reducing the local segment mobility and increasing the free volume at cross‐linking points. The decrease in local segment mobility has been confirmed by the decrease of mean square displacement (MSD) at the cross‐linking points, which is consistent with the change of measured polarization and conductance loss. In the glassy state, the dielectric properties of different anhydride‐cured systems can be reflected by local MSD at the cross‐linking points. At high temperatures near the glass transition temperature, both the free volume and network mobility increase significantly, which reflects the increased dielectric relaxation strength and conductance loss. The understanding of the structure–property relationships could provide a theoretical foundation for epoxy modification in a controlled manner for power equipment applications.

Pathophysiology of acute graft-versus-host disease from the perspective of hemodynamics determined by dielectric analysis.

Numerous reports have demonstrated that the pathophysiology of graft-versus-host disease (GVHD) during hematopoietic stem cell transplantation (HSCT) is closely related to vascular endothelial disorders and coagulation abnormalities. We previously presented the discovery of a principle and the development of a novel instrument for measuring whole blood coagulation. This was achieved by assessing the variations in the dielectric properties of whole blood. To investigate how GVHD affects the changes of dielectric properties of whole blood in patients with HSCT. We examined the changes of dielectric properties of whole blood and erythrocyte proteins by sodium dodecyl sulfate-polyacrylamide gel electrophoresis sequentially in patients with HSCT and compared it with clinical symptoms and inflammatory parameters of GVHD. During severe GVHD, the dielectric relaxation strength markedly increased and expression of band3 decreased. The dielectric relaxation strength normalized with the improvement of GVHD. In vitro analysis confirmed that the increase of relaxation strength was associated with severe erythrocyte aggregates, but not with decreased expression of band3. Severe erythrocyte aggregates observed in GVHD may cause coagulation abnor malities and circulatory failure, which, together with the irreversible erythrocyte dysfunction we recently reported, could lead to organ failure.

A multi-parameter approach to predicting adhesive bond strength in carbon fiber reinforced composites through surface and dielectric characterization

Accurate assessment of composite adhesive bonds is one of the most crucial challenges in replacing metals with composites for structural materials. In this study, carbon fiber composite bonded lap-shear specimens with bond strengths varying from strong bonds to kissing bonds were manufactured using surface modifications and controlled chemical contaminations. The adherend surfaces were characterized by profilometry, Surface Free Energy (SFE) measurement, Fourier Transform Infrared (FTIR) spectroscopy, and Energy Dispersion Spectroscopy (EDS). The bonded specimens were characterized using Broadband Dielectric Spectroscopy (BbDS). Upon destructive testing, the strength and failure modes of the bonds were studied, and strong correlations were observed with the surface properties of the bonds. The observed trends of dielectric relaxation strength with lap-shear strength confirm the potential of BbDS as an effective non-destructive assessment tool.

Revealing Local Structure and Dynamics in Li-Salt Electrolytes Using Dielectric Relaxation Spectroscopy

Understanding the interplay between local structure and dynamics is critical for establishing design rules for advanced ion-conducting electrolytes. In this work, a set of Li-salt in liquid electrolytes is studied using dielectric relaxation spectroscopy (DRS) to examine correlations between several electrolyte properties, including conductivity, dielectric relaxation time and strength, ionicity, and viscosity. These properties were evaluated by changing ion concentration, solvent type, and anion type. DRS was used to identify relaxation processes associated with the solvent and different ion-solvent coordinating structures, and the dielectric properties are reported for the first time for a majority of these systems. The behavior of viscosity and conductivity were shown to change similarly with concentration when accounting for the local coordinating environment, regardless of the salt or solvent type. τα, the dielectric relaxation time of the solvent-ion complexes, is shown to be independent of ion content at low salt concentrations, when solvent separated ion pairs are the dominant ion-solvent complex. However, at high ion concentrations, a new relationship, a power-law dependence, was identified between molar conductivity and τα, as well as viscosity and τα, demonstrating that the dependence of molar conductivity or viscosity on τα is controlled in part by the solvent type, due to variation in shielding between contact ion pairs and aggregates. In contrast, there was not a clear change in the dependence of molar conductivity or viscosity on τα with changing anion. Furthermore, the effective dipole moments of the ion-solvent complexes were determined, and found to decrease with increasing ion concentration, as contact ion pairs and aggregates form. This systematic analysis of the wide range of Li-salts and solvents, and discussion of relations between different local structures and dynamic processes that contribute to conductivity, helps lay a foundation for the design of new liquid electrolytes.

Predicting the Density-Scaling Exponent of a Glass-Forming Liquid from Complex Dielectric Permittivity Measurements.

One of the challenging problems related to the liquid-glass transition phenomenon is establishing a link between the character of intermolecular interactions and the behavior of molecular dynamics. Introducing the density scaling concept, according to which dynamic quantities, e.g., viscosity or structural relaxation time (τ_{α}) measured at different thermodynamic conditions are expressed as a single universal curve if plotted against ρ^{γ}/T, led to significant progress in solving this problem since the scaling exponent γ defines the steepness of the repulsive part of the intermolecular potential. Herein, we found that relaxation dynamics of van der Waals and H-bonding glass formers, for which the Kirkwood factor (g_{K}) is an isomorph-invariant quantity, satisfy an alternative scaling, logτ_{α} vs T(Δϵ_{s}T)^{-γ}. As a result, the exponent γ is determined from the temperature and pressure evolutions of τ_{α} and dielectric relaxation strength Δϵ-both obtained in a single dielectric experiment, which makes the γ coefficient to be accessed in the future for an extensive database of glass-forming liquids.

Enhanced Dielectric Properties of All-Cellulose Composite Film via Modulating Hydroxymethyl Conformation and Hydrogen Bonding Network.

Cellulose-based dielectrics with attractive dielectric performance are promising candidates to develop eco-friendly electrostatic energy storage devices. Herein, all-cellulose composite films with superior dielectric constant were fabricated by manipulating the dissolution temperature of native cellulose, where we revealed the relationship among the hierarchical microstructure of the crystalline structure, the hydrogen bonding network, the relaxation behavior at a molecular level, and the dielectric performance of the cellulose film. The coexistence of cellulose I and cellulose II led to a weakened hydrogen bonding network and unstable C6 conformations. The increased mobility of cellulose chains in the cellulose I-amorphous interphase enhanced the dielectric relaxation strength of side groups and localized main chains. As a result, the as-prepared all-cellulose composite films exhibited a fascinating dielectric constant of as high as 13.9 at 1000 Hz. This work proposed here provides a significant step toward fundamentally understanding the dielectric relaxation of cellulose, thus developing high-performance and eco-friendly cellulose-based film capacitors.

Engineering Conductivity and Performance in Electrorheological Fluids Using a Nanosilica Grafting Approach

Carbonization is considered an effective process for the preparation of carbon-rich solids for various applications. Raw carbonaceous particles however often possess high electrical conductivity, limiting their applicability in electrorheology. To address this drawback, the carbonaceous particles prepared from glucose through hydrothermal synthesis, followed by thermal carbonization in an inert atmosphere, were subsequently coated by compact and mesoporous nanosilica, giving rise to semiconducting particles. The successful coating was confirmed using transmission electron microscopy and spectroscopic analysis, and the composite particles were further used as a dispersed phase in electrorheological (ER) fluids of concentration 5 wt %. While an ER fluid based on pure carbonized particles caused a short circuit of the measuring device at the electric field of intensity 1 kV mm–1, the ER behavior of its analogue based on mesoporous silica-coated particles was successfully measured up to 3 kV mm–1, giving a high yield stress exceeding even the values estimated for ER fluids based on similar carbonaceous particles coated with a compact silica layer. Even though the conductivity decreased only about one order of magnitude after the coating process, the dielectric properties of the prepared ER fluid differed significantly, the relaxation process was shifted to lower frequencies, and most importantly, the dielectric relaxation strength increased, indicating an increased amount of interactions. The presence of mesoporous nanosilica further enhanced the sedimentation stability of the ER fluids when compared to its analogue with the compact silica coating, expanding the scope of practical applicability.

The Nature of the Low-Temperature Crossover of Water in Hard Confinement.

The dynamics of water confined in mesoporous MIP (2-3 nm pores in size) with silica gel (secondary silica; further, the abbreviation SG will be used) and MAP (10-35 nm pores in size) without SG borosilicate glasses have been studied by broadband dielectric spectroscopy (BDS), nuclear magnetic resonance (NMR), and differential scanning calorimetry (DSC). MIP samples contain secondary silica inside the pores and provide a confinement size of about 2-3 nm, whereas MAP samples are free of secondary silica and provide a confinement size of about 10-35 nm. It is shown by BDS and NMR techniques that water exhibits a dynamic crossover of around 180 K when it is confined in MIP samples. By contrast, water confined in larger pores (MAP) does not exhibit any changes in its relaxation behavior. It is also shown that the crossover temperature depends on the hydration level (the higher the hydration level, the lower the crossover temperature). Below the crossover temperature, we find that water reorientation is isotropic (NMR) and that the temperature-dependent dielectric relaxation strength (BDS) follows the tendency expected for a solid-like material. In contrast, water reorientation is related to long-range diffusion above the crossover temperature, and the dielectric relaxation strength follows the tendency expected for a liquid-like material. Furthermore, the calorimetric results are compatible with crossing a glass transition near 180 K. Finally, the results are discussed within the Gibbs-Thomson model. In this framework, the crossover could be related to ice crystals melting.

Dynamical Susceptibilities of Confined Water from Room Temperature to the Glass Transition.

We confine water to narrow silica pores, where crystallization is suppressed, and determine the dynamical susceptibilities of the liquid from room temperature down to the glass transition by combining broadband dielectric spectroscopy (BDS) with 1H and 2H nuclear magnetic resonance (NMR), in particular, by establishing NMR field-cycling relaxometry. For the correlation times, derivative analysis reveals Vogel-Fulcher-Tammann and Arrhenius regimes at T ≥ 215 K and T ≤ 160 K, respectively, which are separated by a broad crossover region. The continuous transition in the temperature dependence is accompanied by a gradual change from asymmetric high-temperature shapes of the dynamical susceptibilities to symmetric low-temperature ones and by a steady decrease of the dielectric relaxation strength. In the Arrhenius regime (Ea = 0.48 eV) at T ≤ 160 K, 2D 2H NMR spectra reveal quasi-isotropic water reorientation. We rationalize these results in terms of a crossover to an interface-affected, noncooperative relaxation involving both rotational and translational motions.

Characteristics of segmental dynamics in EP/TiO2 nanocomposites and its effect on dielectric breakdown

Epoxy nanocomposites with excellent mechanical, thermal and dielectric properties have potential applications in electrical and power electronic devices. However, due to the complex structure of the interfacial region in nanocomposites, molecular dynamic characteristics and how they relate to macro-dielectric performances still needs to be investigated. In this study, several kinds of epoxy nanocomposites were prepared. Segmental dynamics and charge migration parameters are characterised by a dielectric spectroscopy using the Havriliak–Negami equation. The DC breakdown strength of EP/TiO2 nanocomposites was tested for temperature values between 403 and 433 K, and the influence of segmental dynamic characteristics on DC breakdown was discussed. The results indicate that EP/TiO2 nanocomposites with optimised filler content (0.5 wt%) have lower values of dielectric relaxation strength, characteristic relaxation time and thermal expansion coefficients than other samples and that segment dynamics and charge transport processes are suppressed by nanoparticle incorporation. The DC breakdown strength of EP/TiO2 nanocomposites with filler content initially increases and then decreases at a certain temperature, while it significantly decreases with temperature. Correlation analysis indicates that DC breakdown above the glass transition temperature is dominated by segmental dynamics rather than carrier transport. Owing to the tight bond between the nanoparticle and the epoxy matrix, segmental dynamics are impeded when the proper contents of nanoparticles is incorporated, resulting in a decrease in the free-volume fraction and an increase in DC breakdown strength. However, when the temperature rises, the free volume in the intersection of segments expands due to thermal stimulation and free electrons gain sufficient energy in the free length to trigger DC breakdown, hence DC breakdown strength decreases with temperature.

Dielectric state variables as qualitative indicators of moisture absorption-caused mechanical property degradation in GFRP composite structures

Fiber reinforced polymer (FRP) composites are being used in numerous fields owing to their intrinsic strength to weight ratio and various design benefits. However, these materials are prone to environmental aging, particularly moisture absorption. In essence, absorbed moisture infiltrates the polymer matrix and induces changes in the polymer network through chain scission, plasticization, and other bonding interactions. This causes irreversible damages to the material and significantly decreases mechanical strength. In this study, Broadband Dielectric Spectroscopy (BbDS) has been used to identify the absorption mechanisms in glass fiber reinforced polymer (GFRP) composites by detecting the related polarization mechanisms. Here, results show an increase in the real permittivity and dielectric relaxation strength of the material with moisture absorption and attaining a steady-state once absorption approaches saturation. In this work, moisture-induced degradation of tensile and flexural properties of the material have also been studied and a correlation has been found to exist between the dielectric state variables, absorbed moisture, and the mechanical properties of the material. The correlation resolves the integration of the different material physics involved here and can be used to empirically predict the residual strength of a composite structure using the non-destructive broadband dielectric characterization technique.

Transformation of Cellulose via Two-Step Carbonization to Conducting Carbonaceous Particles and Their Outstanding Electrorheological Performance.

In this study, cellulose was carbonized in two-steps using hydrothermal and thermal carbonization in sequence, leading to a novel carbonaceous material prepared from a renewable source using a sustainable method without any chemicals and, moreover, giving high yields after a treatment at 600 °C in an inert atmosphere. During this treatment, cellulose was transformed to uniform microspheres with increased specific surface area and, more importantly, conductivity increased by about 7 orders of magnitude. The successful transition of cellulose to conducting carbonaceous microspheres was confirmed through SEM, FTIR, X-ray diffraction and Raman spectroscopy. Prepared samples were further used as a dispersed phase in electrorheological fluids, exhibiting outstanding electrorheological effects with yield stress over 100 Pa at an electric field strength 1.5 kV mm−1 and a particle concentration of only 5 wt%, significantly overcoming recent state-of-the-art findings. Impedance spectroscopy analysis showed clear interfacial polarization of this ER fluid with high dielectric relaxation strength and short relaxation time, which corresponded to increased conductivity of the particles when compared to pure cellulose. These novel carbonaceous particles prepared from renewable cellulose have further potential to be utilized in many other applications that demand conducting carbonaceous structures with high specific surface area (adsorption, catalyst, filtration, energy storage).

Predicting Dielectric and Shear-Rheology Properties of Glass-Forming Pharmaceutical Liquids from Each Other: Applications and Limitations.

Acetaminophen, nicotine, and lidocaine hydrochloride were investigated in their deeply supercooled liquid states using oscillatory shear rheology. The mechanical spectra of these drugs are presented in modulus, compliance, as well as fluidity formats. Their frequency profiles can be described via models adapted from the field of charge transport. Inspired by the success of this approach, the Barton-Nakajima-Namikawa relation, best known from the same field, was also tested. When adapted to rheology, this approach interrelates static and dynamic characteristics of viscous flow and was found to work excellently. The temperature dependence of the characteristic shear frequencies was checked against the shoving model, which relates them to the temperature-dependent instantaneous shear modulus and acceptable agreement was found. Combined with shear mechanical literature data on ibuprofen and indomethacin, a modified version of the phenomenological model by Gemant, DiMarzio, and Bishop (GDB) was employed to successfully predict the shape and amplitude of the dielectric spectra for all studied liquids, except for lidocaine hydrochloride. For the latter, the modified GDB model is suggested to aid in mapping out the reorientational part of the dielectric response, while the experimental results are strongly superimposed by ionic conduction phenomena. The reverse transformation, the calculation of rheological spectra based on dielectric ones, is also successfully demonstrated. For the example of acetyl salicylic acid, it is shown how dielectric spectra can be used to even predict rheological ones. The limits of the central parameter governing these mutual transformations, the electroviscoelastic material constant, and indications for its correlation with the dielectric relaxation strength are discussed. For pharmaceuticals characterized by a strong dynamical decoupling of the electrical from the mechanical degrees of freedom, the modified GDB model is not expected to be applicable.

Synthesis of polar polynorbornenes with high dielectric relaxation strength as candidate materials for dielectric applications.

Materials with high dielectric permittivity and dielectric relaxation strength are sought for thermal and pressure sensors and electrical energy generators. However, most polymers have either too low dielectric permittivity or are so polar that their glass transition temperature (Tg) is too high and thus decomposition and side reactions occur before an electric field can polarize the polar groups. Here, we use the power and versatility of ring-opening metathesis polymerization (ROMP) to synthesize polar polymers with high dielectric relaxation strength and Tg significantly below the decomposition temperature. We first synthesized six polar norbornene monomers by conventional esterification, which were then polymerized by ROMP using Grubbs first- and third-generation catalysts. The structure of the polynorbornenes obtained were verified by multinuclear NMR spectroscopy, molecular weights determined by gel permeation chromatography (GPC), and thermal properties evaluated by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Additionally, their dielectric permittivity, conductivity, and dielectric losses were measured at different temperatures and frequencies ranging between 0.1 and 106 Hz.

Comparative analysis of dielectric, shear mechanical and light scattering response functions in polar supercooled liquids

The studies of molecular dynamics in the vicinity of liquid–glass transition are an essential part of condensed matter physics. Various experimental techniques are usually applied to understand different aspects of molecular motions, i.e., nuclear magnetic resonance (NMR), photon correlation spectroscopy (PCS), mechanical shear relaxation (MR), and dielectric spectroscopy (DS). Universal behavior of molecular dynamics, reflected in the invariant distribution of relaxation times for different polar and weekly polar glass-formers, has been recently found when probed by NMR, PCS, and MR techniques. On the other hand, the narrow dielectric permittivity function ε*(f) of polar materials has been rationalized by postulating that it is a superposition of a Debye-like peak and a broader structural relaxation found in NMR, PCS, and MR. Herein, we show that dielectric permittivity representation ε*(f) reveals details of molecular motions being undetectable in the other experimental methods. Herein we propose a way to resolve this problem. First, we point out an unresolved Johari–Goldstein (JG) β-relaxation is present nearby the α-relaxation in these polar glass-formers. The dielectric relaxation strength of the JG β-relaxation is sufficiently weak compared to the α-relaxation so that the narrow dielectric frequency dispersion faithfully represents the dynamic heterogeneity and cooperativity of the α-relaxation. However, when the other techniques are used to probe the same polar glass-former, there is reduction of relaxation strength of α-relaxation relative to that of the JG β relaxation as well as their separation. Consequently the α relaxation appears broader in frequency dispersion when observed by PCS, NMR and MR instead of DS. The explanation is supported by showing that the quasi-universal broadened α relaxation in PCS, NMR and MR is captured by the electric modulus M*(f) = 1/ε*(f) representation of the dielectric measurements of polar and weakly polar glass-formers, and also M*(f) compares favorably with the mechanical shear modulus data G*(f).

Effects of Asymmetric Molecular Architecture on Chain Stretching and Dynamics in Miktoarm Star Copolymers

We use broad-band dielectric spectroscopy (BDS) and small-angle X-ray scattering (SAXS) to investigate the impact of architectural asymmetry in the miktoarm star copolymer on the dielectric polymer relaxations. The miktoarm copolymers studied contain one or two polystyrene (PS) chains of constant molecular weight and two identical poly(cis-1,4-isoprene) (PI) chains with varied molecular weights. Using the chains in the PI block as dielectric probes, we find that the architecturally asymmetric miktoarm star copolymer systems (PSPI2) feature distributions in chain relaxation times and dielectric relaxation strengths that are not dependent on molecular weight or morphology, in stark contrast to the effects of morphological confinement observed for symmetric diblock systems (PS-b-PI or PS2PI2). Along with evidence from the SAXS measurements regarding phase separation, these results are attributed to influences from chain stretching within the framework of the Gaussian chain model for block copolymer systems. As such, the molecular architecture in block copolymers happens to be a versatile handle to control polymer chain dynamics and, ultimately, the macroscopic physicochemical properties in architecturally complex polymers.

Effects of ultralow concentration MXene (nano-Ti3C2Tx) on the electric and physical properties of ternary polyvinyl alcohol composites

High-dielectric-constant (high-κ) fillers are embedded in polymer materials to improve the dielectric constant of polymer and form high-κ composites for the latest generation of energy storage devices. However, the addition of high-κ fillers will introduce interface polarization and cause space charge accumulations that will increase dielectric loss and reduce breakdown strength. Herein introduces a conductive MXene(nano-Ti3C2Tx) with high surface area to remarkably suppress space charge in polyvinyl alcohol (PVA) matrix. A ternary PVA composite with high dielectric constant and low dielectric loss is formed by doping with ultralow concentration MXene and soluble ferroelectric [Hdabco]ClO4 (TEDA.C) via solution mixing. The space charge suppression capability of MXene sharply reduces the dielectric loss of 1M@1788PVA and 5M@1788PVA (PVA with 0.0001 wt.% and 0.0005 wt.% MXene) at low frequency (0.1−10 Hz). By comparing the activation energy of dielectric relaxation (Ea) and breakdown strength (BDS) under AC electric field between pure PVA and PVA composites, ultralow concentration MXene declines the Ea of 1M@1788PVA and 5M@1788PVA by 26.8 % and 60.9 %, and effectively improves the BDS of 1M@1788PVA and 1M5T@1788PVA (PVA with 0.0001 wt.% MXene and 4.7 wt.% TEDA.C) by 3%. The addition of ultralow concentration MXene and TEDA.C bring 5M5T@1788PVA(PVA with 0.0005 wt.% MXene and 4.7 wt.% TEDA.C) highest discharged energy density(17.32 J/cm3)which is 1.53 times of that of 1788PVA.

Miscibility of Poly(Methyl Methacrylate) and Poly(Vinylidene Fluoride) Examined by Thermally Stimulated Depolarization Current and Dielectric Relaxation Spectroscopy

Samples of poly(methyl methacrylate) (PMMA), poly(vinylidene fluoride) (PVDF) and melt blended PMMA/PVDF with weight ratios 4/1 and 3/2 were characterized by thermally stimulated depolarization currents (TSDC) in the temperature interval 123-303 K and by dielectric relaxation spectroscopy (DRS) in the frequency window 10−2 − 106 Hz in the temperature interval 153-423 K. The TSDC thermograms and DRS profiles of the samples showed the two types of conducnivity – non-cooperative and cooperative. The experimental DRS data in the vicinity of the glass transition temperature, Tg, were quantitatively fitted to the Havriliak-Negami function and values of the maximum relaxation time were fitted to the Vogel-Tammann-Fulcher equation. Higher values of the strength index D, of the dielectric relaxation strength Δε and of the σ ac conductivity for the binary blends were considered as experimental evidence for nanoscale composition heterogeneities originating from strong specific interactions between the PMMA and PVDF. Therefore, we suggest the PMMA/PVDF blends will be usefull as effective materials for the manufacture of lithium-ion batteries, electrostatic capacitors with superior energy storage performance, polymer composite electrolytes for solar cells, etc.

Ferroelectric behavior in paracrystalline poly(vinyl trifluoroacetate)

Abstract Dielectric behavior in paracrystalline poly(vinyl trifluoroacetate) was investigated from the viewpoint of ferroelectricity. This polymer has a large CF3 dipole moment (2.3 Debye) and structural defects due to the atactic sequence in its chain conformation. It is possible to rotate the dipoles in paracrystals with defects under high electric field. The dielectric behavior was measured from 20 to 200 °C. A large dielectric constant and dielectric relaxation strength (Δε = 17 at 110 °C) were observed in the α-relaxation region. Corona poling on the samples was carried out at DC field 80 MV/m and 80 °C. Ferroelectric D–E hysteresis loop was observed under high electric field, and the remanent polarization and coercive field at 40 °C were 15 mC/m2 and 155 MV/m, respectively. Pyroelectric response and thermally stimulated current were measured from the current through the electrode irradiated by a pulsed semiconductor laser. A pyroelectric constant of about 6 μC/m2K was observed, which was stable up to near the poling temperature. The ferroelectricity in poly(vinyltrifluoroacetate) stems from the rotation of molecular chains in its paracrystals and orientation of the CF2 dipoles. Poly(vinyltrifluoroacetate) dielectrics can be used for capacitors with high power density, artificial skins, muscles and other flexible electronics.