High Dielectric Response Research Articles

Novel One-Dimensional Organic–Inorganic Hybrid Halide Perovskite Material with Coexistence of High Phase Transition Temperature and Corresponding Dielectric Response

Novel One-Dimensional Organic–Inorganic Hybrid Halide Perovskite Material with Coexistence of High Phase Transition Temperature and Corresponding Dielectric Response

High field dielectric response in κ-Ga2O3 films

κ-Ga2O3 has been predicted to be a potential ferroelectric material. In this work, undoped Ga2O3 films were grown by either plasma-enhanced atomic layer deposition (PEALD) or metal organic chemical vapor deposition (MOCVD) on platinized sapphire substrates. 50 nm thick PEALD films with a mixture of κ-Ga2O3 and β-Ga2O3 had a relative permittivity of ∼27, a loss tangent below 2%, and high electrical resistivity up to ∼1.5 MV/cm. 700 nm thick MOCVD films with predominantly the κ-Ga2O3 phase had relative permittivities of ∼18 and a loss tangent of 1% at 10 kHz. Neither film showed compelling evidence for ferroelectricity measured at fields up to 1.5 MV/cm, even after hundreds of cycles. Piezoresponse force microscopy measurements on bare κ-Ga2O3 showed a finite piezoelectric response that could not be reoriented for electric fields up to 1.33 MV/cm.

Rare earth ion-infused α-MnO2 nano-rods for excellent EMI shielding efficiency: Experimental and theoretical insights

In this communication, for the first time rare earth elements like Gd3+ and Er3+ ions are impregnated into the α-MnO2tunneled structure involving the modified chemical synthesis route followed by hydrothermal technique. X-ray diffraction patterns and Raman spectroscopy confirm the proper phase formation without any impurity. A theoretical in-depth DFT study for the electronic bands and variation of density of states with the infusion of rare earth elements into the host structure confirms the experimental findings and depicts the suitability of the material for the EMI shielding application. The novel synthesis technique helps to achieve uniform nanorod formation with a high specific surface area. Doping-induced defects, high surface-to-volume ratio, Maxwell-Wagner–Siller interfacial polarization, etc. lead to achieving high dielectric response with moderate tangent loss at a frequency range of 40 Hz to 1 MHz. Temperature-dependent dielectric behavior indicates the paramagnetic to ferromagnetic transition at 120 °C and 70 °C for the Gd- and Er-doped α-MnO2 samples respectively. The electromagnetic interference (EMI) shielding effectiveness (SE) has achieved a maximum of −43 dB at 15.3 GHz and − 46 dB at 15.3 GHz for Gd- and Er-doped α-MnO2 thin layer of thickness ∼600 μm respectively. Higher dipolar polarization, loss tangent, conductive pathways, and defects inside the crystal lead to attaining a high EMI shielding efficiency. This result reveals >99.997% EMI SE against the hazardous electromagnetic waves in the microwave/GHz frequency region.

Smart and Multifunctional Materials Based on Electroactive Poly(vinylidene fluoride): Recent Advances and Opportunities in Sensors, Actuators, Energy, Environmental, and Biomedical Applications.

From scientific and technological points of view, poly(vinylidene fluoride), PVDF, is one of the most exciting polymers due to its overall physicochemical characteristics. This polymer can crystalize into five crystalline phases and can be processed in the form of films, fibers, membranes, and specific microstructures, being the physical properties controllable over a wide range through appropriate chemical modifications. Moreover, PVDF-based materials are characterized by excellent chemical, mechanical, thermal, and radiation resistance, and for their outstanding electroactive properties, including high dielectric, piezoelectric, pyroelectric, and ferroelectric response, being the best among polymer systems and thus noteworthy for an increasing number of technologies. This review summarizes and critically discusses the latest advances in PVDF and its copolymers, composites, and blends, including their main characteristics and processability, together with their tailorability and implementation in areas including sensors, actuators, energy harvesting and storage devices, environmental membranes, microfluidic, tissue engineering, and antimicrobial applications. The main conclusions, challenges and future trends concerning materials and application areas are also presented.

Dielectric response as a novel marker for ablation lesion quality: Relation to conventional ablation parameters.

The tissue response viewer (TRV) is a novel marker for ablation lesion quality that aims to classify lesions into transmural or nontransmural lesions (high or low dielectric response, HDR or LDR) using dielectric-based tissue assessment. The objective of this study was to gain insight in the TRV by relating its outcomes to conventional ablation parameters. Patients that had repeat ablation for atrial fibrillation with a dielectric imaging-based mapping system were enrolled. All ablation data were downloaded from the mapping system and analyzed to explore associations between TRV outcomes and other ablation parameters. The cohort included 24 patients, in which 58 pulmonary veins and 8 superior vena cavas were targeted. A total of 388 energy applications were applied, resulting in 639 ablation points. The system classified 36% of ablation points as HDR and 44% as LDR. The system did not provide a dielectric response in 20%. The system's ability to provide a dielectric response was related to longer ablation duration and absence of dragging ablation. HDR (versus LDR) was multivariably associated with longer energy applications, higher mean ablation power, and lower wall thickness. Greater impedance drop was univariably associated with HDR. Outcomes of the TRV are associated with conventional ablation parameters (e.g., duration and power) but also local wall thickness. Catheter stability seems important for successful lesion assessment with the TRV. Further reduction of missing outcomes and validation of the tool are warranted before widespread use.

Dielectric response in relation to other ablation parameters

Abstract Funding Acknowledgements Type of funding sources: None. Background Dielectric imaging is used by the KODEX-EPD system to provide information that can be used to guide catheter ablation of cardiac arrhythmia. This includes assessment of catheter-tissue contact (No touch, Touch, or High touch) and local atrial wall thickness (mm). Additionally, the system can detect changes in local dielectric tissue properties to assess the effect of a radiofrequency energy application. This assessment is used to classify ablation points into low or high dielectric response (LDR or HDR), which was designed to indicate the extent of lesion transmurality. Objectives To evaluate the relation between dielectric response and other ablation parameters. Methods The KODEX-EPD system was used to guide ablation in patients with prior pulmonary vein isolation. Ablation included re-isolation of the pulmonary veins and isolation of the superior vena cava if deemed necessary. We downloaded system data from all procedures that were performed with software that provided dielectric response (version 1.5.0, 1.5.0a, 1.5.1 and 1.5.1a) and analyzed the parameters of all individual ablation points. Results The cohort includes 55 patients, in which 135 pulmonary veins and 19 superior venae cavae were targeted. A total of 860 energy applications were applied, resulting in 1458 ablation points. The system classified 31% of ablation points as HDR and 19% as LDR. The system did not provide a dielectric response in 49%. The system’s ability to determine dielectric response was related to the software version(oldest version 71% no DR, newest version 18%) and duration of ablation. High dielectric response (versus LDR or no DR) was multivariably associated with longer energy applications, higher mean ablation power and lower local wall thickness (Table). Mean ablation temperature and impedance drop were not multivariably associated with dielectric response. Conclusion Dielectric response is independently associated with local wall thickness, ablation power and duration, but not with ablation temperature and impedance drop. Newer software versions have reduced the proportion of ablation points for which no dielectric response was provided.

High dielectric response of TaOX thin film and its modification by controlling oxygen vacancy concentration

High dielectric response of TaOX thin film and its modification by controlling oxygen vacancy concentration

Fast Detection Method on Water Tree Aging of MV Cable Based on Nonsinusoidal Response Measurement

A MV power cable will exhibit nonlinear impedance when dendritic defects appear. To solve the long time-consuming measurement of pure sinusoidal excitation and realize rapid and accurate evaluation of insulation conditions, a measurement and evaluation method based on nonsinusoidal excitation is proposed in this paper. Firstly, a nonsinusoidal excitation test system is established, which can obtain the high voltage dielectric response in the frequency range of 0.01 Hz–1 kHz. For parameterizing dielectric response characteristics of MV XLPE insulation under nonsinusoidal excitation, a Hammerstein-Wiener model is proposed to realize system parameter identification under non sinusoidal excitation with different aging degrees of water tree. The time-domain current response waveform based on the H-W model is more accurate than the traditional linear model, and the resulting fitting degree of the frequency-domain dielectric loss factor curve between the calculated H-W model and the measured curve was higher than 95%. The results show that the rotation and distortion of the u-i hysteresis ellipse under nonsinusoidal excitation can be used to diagnose the insulation defects of XLPE MV cables. The response model and its detection method proposed in this paper can improve the efficiency and accuracy of the field tests of cable insulation.

The effect of tailoring morphology on rheology and dielectric properties of poly (lactic acid) /thermoplastic polyurethane/graphene oxide nanocomposites

To develop eco-friendly elastomeric nanocomposites with high dielectric response, poly(lactic acid) (PLA) was melt compounded with varying amounts of thermoplastic polyurethane(TPU) and a fixed loading of (3 wt.%) graphene oxide(GO). The electrical and dielectric properties of the nanocomposites, in terms of TPU and GO loadings and selective localization of GO nanoplatelets, were correlated with morphological and rheological properties. The results exhibit that inclusion of 3 wt.% GO to PLA/TPU blend leads to nearly 400% improvement in the dielectric constant at high TPU loadings. Increasing the TPU content results in morphological transformation in which a sea-island structure changes to a near co-continuous structure. In addition, in the near co-continuous structure, the selective localization of GO nanoplatelets in the TPU phase and at the interface results in the formation of nano-network percolation at a lower frequency, reflected in both rheological and electrical properties. More conductive paths as well as denser nano-networks in near co-continuous nanocomposite are responsible for higher electrical properties. Near Co-continuous nanocomposites with higher dielectric and electrical properties exhibit higher storage and loss modulus. In short, selective localization of GO and strong conductive path in conjunction with a near co-continuous morphology result in 100% improvement in dielectric response as compared to the system with the sea-island morphology. • Found higher dielectric properties for systems with near co-continuous morphology • Percolated nano-network formed by selective localization of GO in TPU continuous phase • Obtained higher electrical properties, storage and loss moduli for co-continuous nanocomposites • Nearly 400% improvement in dielectric constant achieved at high TPU loadings

Initial experience with dielectric-based local tissue assessment for catheter ablation

Abstract Background Dielectric imaging systems can be used to guide catheter ablation for cardiac arrhythmia. Currently, the KODEX-EPD system can be used to acquire high-resolution anatomical data for electroanatomical mapping. Future software versions of this system enable tissue assessment utilizing local dielectric sensing. These dielectric-based tissue assessments (KODEX Vision) enable new features, including wall thickness measurement, catheter-tissue contact assessment, and ablation lesion assessment. Purpose To gain insight in the dielectric-based tissue assessment features. Methods The KODEX-EPD system was used to perform repeat ablations in patients with recurrent atrial fibrillation after pulmonary vein isolation. A primary system with the current software version (1.4.8) was used by the operator. Ablation was performed with a non-contact force-sensing irrigated radiofrequency catheter, with power set at 30–35W and aiming for ablation times of 30–60s. A secondary system was blinded for the operator and loaded with beta software (1.5.0) to enable the KODEX Vision features. Only successful local tissue assessments are presented in this abstract. All patients were enrolled in a prospective registry study which was approved by the local ethics committee. Results Electroanatomic mapping in 25 patients (age 65±8yr, male 84%, LAVI 31±9ml/m2) revealed electrical reconnection in 66 of 100 pulmonary veins. A total of 308 radiofrequency applications were used to re-isolate the veins and create additional lesions (superior vena cava isolation in 6, box lesion in 1). Wall thickness at the sites of ablation ranged from 1.3–3.9 mm. Tissue contact assessment at the start of RF applications indicated “touch” in 77%, while 17.5% and 5.5% of results indicated `no touch' or “high touch”. Tissue Response Viewer indicated low dielectric response in 18.5% and high dielectric response in 81.5% of results. High dielectric response was associated with lower wall thickness (OR: 0.86, 95% CI [0.76–0.97], p=0.014). Conclusion This preliminary evaluation underlines the potential of dielectric-based tissue assessment features. Wall thickness measurement, catheter-tissue contact, and ablation lesion assessment seem feasible with the beta software. Further evaluation of the feasibility, accuracy and clinical impact of the finalized software is warranted. Funding Acknowledgement Type of funding sources: None.

Giant Dielectric Response of Corundum Structure Fe0.7Cr1.3O3 Nanocrystallite

We report the structure and dielectric properties of Fe0.7Cr1.3O3 nanocrystallites synthesized by co-precipitation method. X-ray diffraction shows that the nanoparticles possess a typical corundum structure and no other impurity phases are observed. These nanoparticles exhibit a high dielectric permittivity (ε′ ∼ 103) at room temperature below 1 kHz. The dielectric relaxation follows the thermally activated process with activation energy of 0.226 eV. Both components of grain relaxation and grain boundary relaxation times were extracted from modulus spectra. The internal barrier layer capacitance (IBLC) effect is responsible for observed high dielectric response in these nanoparticles.

Experimental discovery of structure–property relationships in ferroelectric materials via active learning

Emergent functionalities of structural and topological defects in ferroelectric materials underpin an extremely broad spectrum of applications ranging from domain wall electronics to high dielectric and electromechanical responses. Many of these functionalities have been discovered and quantified via local scanning probe microscopy methods. However, the search has until now been based on either trial and error, or using auxiliary information such as the topography or domain wall structure to identify potential objects of interest on the basis of the intuition of operator or pre-existing hypotheses, with subsequent manual exploration. Here we report the development and implementation of a machine learning framework that actively discovers relationships between local domain structure and polarization-switching characteristics in ferroelectric materials encoded in the hysteresis loop. The hysteresis loops and their scalar descriptors such as nucleation bias, coercive bias and the hysteresis loop area (or more complex functionals of hysteresis loop shape) and corresponding uncertainties are used to guide the discovery of these relationships via automated piezoresponse force microscopy and spectroscopy experiments. As such, this approach combines the power of machine learning methods to learn the correlative relationships between high-dimensional data, as well as human-based physics insights encoded into the acquisition function. For ferroelectric materials, this automated workflow demonstrates that the discovery path and sampling points of on- and off-field hysteresis loops are largely different, indicating that on- and off-field hysteresis loops are dominated by different mechanisms. The proposed approach is universal and can be applied to a broad range of modern imaging and spectroscopy methods ranging from other scanning probe microscopy modalities to electron microscopy and chemical imaging.

High voltage dielectric response characteristics of oil-paper insulation with different moisture content

High voltage dielectric response characteristics of oil-paper insulation with different moisture content

Enabling high dielectric response and low electrical leakage in polymer/mesoporous-silica@CdTe-quantum-dots nanocomposites by excitonic dipoles and pore-canal restriction

High dielectric response and low leakage conduction are desired in polymer/ceramic composite dielectrics for capacitive energy storage. Rational structural design of hybrid ceramic filler can lead to a balance between high dielectric constant and insulation in composites. In this study, high dielectric constant and breakdown strength were achieved in fluoropolymer/mesoporous silica@CdTe nanocomposite films. Mesoporous silica nanoparticles (MSNs) were employed owing to their high insulation and complex electron-leakage channel. CdTe quantum dots combined with pore-canal inwalls of MSNs were employed because of their internal exciton polarization and MSNs/CdTe interface polarization. Compared with polymer/MSNs composites, polymer/MSNs@CdTe composites exhibited remarkably improved dielectric constant, slightly increased dielectric loss, and slightly reduced breakdown strength. High dielectric constant of ternary composites was ascribed to exciton orientation inside CdTe and interfacial dipole orientation between MSNs and CdTe. High breakdown strength was attributed to high insulation in MSNs and long-range electron transfer inside MSNs@CdTe. An optimal ternary composite with 12 wt% MSNs@CdTe showed a high dielectric constant of ~56, low dielectric loss of ~0.19 at 100 Hz, and high breakdown strength of ~308 MV m-1. The results of this study can provide insights for enabling large-scale fabrication of modern composite dielectrics based on mesoporous particles@semi-conductive quantum dots fillers.

Coupling of ethanolamine ammonia-lyase protein and solvent dynamics characterized by the temperature-dependence of EPR spin probe mobility and dielectric permittivity.

Electron paramagnetic resonance (EPR) spectroscopy is used to address the remarkable persistence of the native Arrhenius dependence of the 2-aminopropanol substrate radical rearrangement reaction in B12-dependent ethanolamine ammonia-lyase (EAL) from Salmonella typhimurium from physiological to cryogenic (220 K) temperatures. Two-component TEMPOL spin probe mobility in the presence of 10 mM (0.08% v/v) 2-aminopropanol over 200-265 K demonstrates characteristic concentric aqueous-cosolvent mesodomain and protein-associated domain (PAD, hydration layer) solvent phases around EAL in the frozen solution. The mesodomain formed by the relatively small amount of 2-aminopropanol is highly confined, as shown by an elevated temperature for the order-disorder transition (ODT) in the PAD (230-235 K) and large activation energy for TEMPOL rotation. Addition of 2% v/v dimethylsulfoxide expands the mesodomain, partially relieves PAD confinement, and leads to an ODT at 205-210 K. The ODT is also manifested as a deviation of the temperature-dependence of the EPR amplitude of cob(II)alamin and the substrate radical, bound in the enzyme active site, from Curie law behavior. This is attributed to an increase in sample dielectric permittivity above the ODT at the microwave frequency of 9.5 GHz. The relatively high frequency dielectric response indicates an origin in coupled protein surface group-water fluctuations of the Johari-Goldstein β type that span spatial scales of ∼0.1-10 Å on temporal scales of 10-10-10-7 s. The orthogonal EPR spin probe rotational mobility and solvent dielectric measurements characterize features of EAL protein-solvent dynamical coupling and reveal that excess substrate acts as a fluidizing cryosolvent to enable native enzyme reactivity at cryogenic temperatures.

Improving electric insulation characteristics of PVA/V2C MXene composite high-dielectric-constant films by blending cellulose

Polymer/conductor composite dielectrics easily have high permittivity, high conductivity, and high dielectric loss, limiting large increase of energy storage density in them. The relationship between high permittivity and low conductivity is coordinated to achieve high energy density. In this study, polyvinyl alcohol (PVA)/V2C MXene/cellulose ternary composites with high permittivity and low dielectric loss were prepared. Due to good water solubility of PVA and high water dispersibility of V2C, PVA and V2C have good interfacial compatibility. That reduces the interface electric leakage conductance, which is conducive to the lower conductivity and dielectric loss in the composite materials. The high interfacial polarization between PVA and V2C improves the dielectric response of the composite materials, improving the permittivity of the composite materials. Compared with binary PVA/V2C composites, ternary PVA/V2C/cellulose composite materials use the high insulation of cellulose filler to increase the insulation of composites. Thus, the conductivity and dielectric loss are reduced in ternary composites. Good synergy of conductive V2C and insulating cellulose fillers is important to obtaining the balance of high dielectric response and high insulation trait in ternary composites. Best ternary composite with 6 wt% V2C has a high permittivity of ca. 40, low dielectric loss of ca. 0.25 at 100 Hz, and high breakdown strength of ca. 40 MV m−1. This work enables a facile preparation of promising composites for dielectric energy storage. • Novel ternary composite dielectric films with V 2 C MXene and cellulose were fabricated. • Good synergy of V 2 C and cellulose can lead to optimization of overall electric properties. • This work might provide ideas for preparing bio-dielectric materials employing cellulose.

Remarkably improving dielectric response of polymer/hybrid ceramic composites based on 0D/2D-stacked CuO/V2C MXene heterojunction

High dielectric response and electric insulation are desired in high-energy-density polymer/ceramic composites. Low dielectric response is found in polymer composites with semiconductors. To balance a high dielectric constant and breakdown strength, in this work, the polymer-based composites with de novo synthesized V2C MXene-CuO hybrid-particles were fabricated. High dielectric response of composites was attributed to strong electron polarization at ceramic/ceramic heterojunction. High insulation was ascribed to fluorine-induced electron-trap effect. The first principle calculations verified the electron-transfer mechanism at V2C/CuO van der Waals heterojunctions. Compared with polymer/CuO binary composites, polymer/V2C-CuO ternary composites exhibited the improved comprehensive electric properties (remarkably improved dielectric response and slightly damaged insulation). Ternary composite with 10 wt% V2C-CuO showed a high dielectric constant of 89, low dielectric loss of 0.23, low conductivity of 6.8 × 10−7 S m−1 at 100 Hz and high breakdown strength of 204 MV m−1. This study might enable a facile preparation of cutting-edge nanocomposite dielectrics.

High dielectric constant poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene) for capacitive pressure and bending sensors

Poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene), P(VDF-TrFE-CFE), samples were prepared by solvent casting by varying polymer concentration and solvent evaporation temperature. Different sample morphologies were obtained depending on the processing conditions, as well as different physical-chemical properties such as degree of crystallinity, mechanical and dielectric properties. On the other hand, the electroactive β-phase content and the degradation temperature of the P(VDF-TrFE-CFE) samples are independent of the processing conditions. At 1 kHz, the highest dielectric constant, ε’ = 40, was obtained for the samples prepared with 15 wt% polymer concentration in solutions and processing conditions based on solvent evaporation and polymer melting at 210 °C. Taking into account the high dielectric response, pressure and bending capacitive sensors were developed with excellent response and high sensibility (0.03 kPa−1). The developed materials were evaluated for bending and force detection applications. Thus, it is concluded that the developed P(VDF-TrFE-CFE) films are suitable for a new generation of multifunctional materials for capacitive sensing applications, including both force and deformation sensors and touchpads.

Enabling High Dielectric Response in PVDF/V2C MXene–TiO2 Composites Based on Nontypical V–F–Ti Bonding and Fermi-Level Overlapping Mechanisms

High dielectric constant and breakdown strength are crucial for high-energy-density polymer/ceramic composites. Anatase-TiO2 with low dielectric constant and V2C MXene with high work function are n...

Local Structure Analysis around Ti in Lead Zirconate Titanate by X‐Ray Fluorescence Holography

To clarify the mechanism of ferroelectricity in lead zirconate titanate (PZT), the local structure around Ti in a Pb(Zr0.7Ti0.3)O3 single crystal is investigated using X‐ray fluorescence holography. The raw hologram data are contaminated by periodic noise due to the fluctuation of the incident X‐ray intensity. The periodical noise is successfully removed using an inverse Fourier transformation method. From the filtered holograms, the atomic images around Ti can be reconstructed clearly. The reconstructions of B‐site cations demonstrate an outward displacement of the neighboring Ti from the ideal B‐site position, indicating an expansion of the local lattice around Ti. In addition, the splitting of Pb images is found, and the relative displacement between Ti and Pb atoms is deduced. These results contribute to the understanding of the local structure of PZT and can reveal the microscopic origins of very high dielectric and piezoelectric responses, which are essential for designing new and improved ferroelectric materials.