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The exploration of dielectric ceramics with excellent dielectric responses at Gigahertz band and Terahertz band is becoming urgent for the upcoming 6th generation wireless communication. In this work, we propose a new approach to design novel dielectric ceramics by using the density functional theory. According to the analysis of Electron Localization Functions (ELF), Density of States (DOS) and crystal bond lengths, it indicates that the strategy of co-doping with lithium and fluorine will contribute to a much more stable crystal structure of Li 0.5 NaY 9 (SiO 4) 6 O 2 F 0.5 as compared to that of NaY 9 (SiO 4) 6 O 2. Furthermore, we report the innovative synthesis of a Li 0.5 NaY 9 (SiO 4) 6 O 2 F 0.5 oxyfluoride ceramic, a solid solution with a wide sintering temperature range, along with an in-depth analysis of its crystal structure, dielectric responses at both Gigahertz band and Terahertz band, which shows the promising application of Li 0.5 NaY 9 (SiO 4) 6 O 2 F 0.5 in the 6G wireless communication. [ABSTRACT FROM AUTHOR]

ABSTRACT The exceptional optoelectronic capabilities of all‐inorganic metal halide perovskite semiconductor components open up a multitude of possible applications. Among all the metal halides, the chloride of cesium cadmium has not been investigated in great detail. Here, we describe a straightforward method for creating CsCdCl3 perovskite single crystals using the slow evaporation solution growth approach. These were investigated by utilizing X‐ray powder diffraction, and optical and impedance spectroscopies. The creation of a single‐phase with a hexagonal‐type structure was verified by the X‐ray powder diffraction (XRPD) data. The compound's semiconductor characteristics were verified by the optical measurement, indicating a direct band‐gap value of about 3.16 eV. The absorption and reflectance spectrum was also used to calculate and explain the optical extinction coefficient, Urbach energy, and skin depth as functions of the input photon's wavelength. Besides, the impedance spectroscopy technique was employed to investigate the characteristics of this component, across a frequency range of 10−1 Hz to 106 Hz and at temperatures ranging from 313 K to 453 K. The frequency behavior of the AC conductivity, σac, was analyzed using the universal Jonscher law. The outcomes of the charge transport investigation on CsCdCl3 imply that the perovskite material possessed a quantum mechanical tunneling (QMT) model for T < 363 K and a large polaron tunneling (OLPT) paradigm for T > 363 K. A correlation between the ionic conductivity and the crystal structure was established and discussed. Ultimately, the low dielectric loss and high dielectric constant of CsCdCl3 make it a promising material for energy harvesting devices. [ABSTRACT FROM AUTHOR]

The novel double perovskite oxide SrEuTiFeO6 was synthesized using the solid‐state reaction method. X‐ray diffraction analysis, complemented by Rietveld refinement, confirmed that this material crystallizes in a cubic double perovskite structure with the Pm3̅m space group and revealed cationic disorder at both the A (Sr, Eu) and B (Ti, Fe) sites. Crystallite size and lattice strain were determined through various methods. Fourier‐transform infrared spectroscopy was utilized to examine vibrational modes and bond distortions within this material. Scanning electron microscopy showed a heterogeneous microstructure, with a wide distribution of grain sizes and shapes, resulting from the kinetics of the solid‐state synthesis. Energy dispersive X‐ray spectroscopy confirmed the material's homogeneity, stoichiometry, and chemical composition. UV–visible spectroscopy was used to investigate the optical properties of SrEuTiFeO6, identifying several characteristic optical transitions. The band gap energy and refractive index were found to be 2.08 eV and 2.60, respectively, indicating the material's potential for various applications. Additionally, the dielectric properties, including the relative dielectric constant and loss tangent, were thoroughly analyzed as functions of frequency and temperature. The electrical conductivity dispersion phenomenon was also analyzed according to Jonscher's power law, revealing the predominance of overlapping the large polaron tunneling mechanism. [ABSTRACT FROM AUTHOR]

Metal single‐atoms implanted on nitrogen‐doped carbon matrices (M‐NxCs) can effectively adjust local surface electrons and polarization relaxation through coordination structures to significantly enhance the electromagnetic wave (EMW) absorption properties of the materials. However, the precise construction of the geometric and electronic structures of metal single atoms and the discovery of the structure‐absorption relationship at the atomic level confront a huge challenge. Herein, this work summarizes the latest progress in metal single‐atom engineering of EMW absorbing materials via a comprehensive analysis of M‐NxCs in terms of design principles, modulation strategies, and structure‐performance correlations. Subsequently, it highlights the recent progress of several typical M‐NxCs as the EMW absorbing materials, aiming to achieve a complete understanding of the physical effects and atomic‐level absorption mechanisms. Finally, current key challenge and future directions of M‐NxCs are presented by focusing on the electromagnetic functional materials. This work provides new insights for the development of atomically dispersed absorbing materials for efficient electromagnetic response functionalities. [ABSTRACT FROM AUTHOR]

The dielectric response of M-hexaferrite nanoceramics is complex since it is determined by crystal structure and microstructure. We studied the dielectric behavior of Nd3+ modified Sr2 + Fe12O19 nanoceramics with ferric ions, responsible for magnetic properties, substituted by Sc3+ and Al3+. To compare the effect of different ionic radii we discussed the dielectric response of Sr0.95Nd0.05Fe12-xScxO19 and Sr0.95Nd0.05Fe12-xAlxO19 at the doping level of x = 1.08. The dielectric response was found to consist of four contributions: (i) Low-temperature dispersion of dielectric polarization created by doping-induced spin-canting. The polarization, described by the inverse Dzyaloshinskii-Moriya model, is in nanoceramics limited by the shape and size of the crystallites. (ii) Changes in relaxation modes of polar vacancies due to interaction with electric dipole moments modified by deformation of oxygen octahedra. (iii) Dielectric dispersion in room temperature range related to space charge relaxation in grain boundaries. (iv) High-temperature electric conductivity of the grain interiors. [ABSTRACT FROM AUTHOR]

High-voltage dielectric and AC conduction behaviors of epoxy resin (EP) insulation are beneficial for the design and application of solid-state power electronic devices. This study investigates the nonlinear dielectric response and AC conduction characteristics of EP. The dielectric relaxation characteristics, including permittivity and AC conductivity of the EP samples, were investigated using high-voltage dielectric spectroscopy and the ionic polarization model. The results demonstrate a nonlinear increase in the relative permittivity and AC conductivity concerning the AC electric field. The increase in AC conduction under a high-frequency electric field is attributed to the reduction in the threshold field for charge injection caused by elevated temperatures. Considering the dielectric response and carrier hopping, it is evident that the nonlinear dielectric response of EP primarily originates from the ionic process under high electric fields. Ionic polarization, in conjunction with ion-hopping conduction, enhances the dielectric loss at high frequencies and electric fields, thereby facilitating the nonlinear conversion of AC conduction. The equivalent free volume is likely to increase in high-frequency fields. This phenomenon leads to an increase in AC conduction and even dielectric breakdown. This study offers a pivotal theoretical framework for the design and application of high-frequency insulation. [ABSTRACT FROM AUTHOR]

We synthesized polycrystalline samples of Ba0.97La0.02Ti1−xNb4x/5O3, denoted as BLTi1 − xNb4x/5, with varying doping levels (x = 0.00, 0.02, and 0.05) through the Molten-Salt process. Introducing niobium had a significant impact on the physical characteristics of the BLT polycrystalline ceramics. Analysis via X-ray diffraction (XRD) indicated the presence of a single phase across all doping concentrations. As the concentration of Nb increased, there was a noticeable decrease in the typical size of crystallites. Scanning electron microscopy (SEM) revealed the formation of non-uniform particles as conventional grain size decreased with doping. We then investigated dielectric properties concerning frequency and composition under zero bias potential. Dielectric dispersion observed was interpreted utilizing both the Koops phenomenological theory and the Maxwell-Wagner interfacial model. Overall, under zero bias potential, Nb doping significantly impacted the electrical conductivity of BLT polycrystalline materials. [ABSTRACT FROM AUTHOR]

This study is reporting the role of embedded ferroelectric ceramics Bi4Ti3O12 (BTO = 1–5 wt%) into the polyvinylidene fluoride (PVDF) composites on its structural, bonding, surface morphology, and dielectric response. Especially lead free flexible composite electrodes have lot of attention due to its high dielectric permittivity and energy storage density. X‐ray diffraction spectra confirms monophasic orthorhombic structure of composites, while Fourier transform infrared (FTIR) spectra confirms the bonding behavior. Scanning electron microscopy (SEM) images surface morphology of homogeneously distributed ceramic particles with interconnected network. Dielectric constant has been found to be improved from 9.56 to 13.73 for BTO5%PVDF95% composites at frequency of 1 kHz attributes promoted interfacial polarization of PVDF and effectively limited the charge leakage in the composites, implying promising applications in flexible electronic devices. [ABSTRACT FROM AUTHOR]

Graphene nanoplatelets/polydimethylsiloxane (GNPs/PDMS) nanocomposites foils are obtained by dispersing nanoplatelets of graphene (GNPs) into polydimethylsiloxane (PDMS) at a given GNPs concentration but at different curing times to study the effects of curing time on some their bulk and surface properties. Their appearance and morphology have been examined by optical and scanning electron microscopies, their wettability and roughness by the sessile drop method and profilometry, their bonds by µRaman and ATR-FTIR spectroscopies, their dielectric response by dielectric spectroscopy. In particular, optical and SEM images and roughness measurements indicate a roughened and hydrophobic surface at the shortest curing time that becomes less roughened, more uniform and less hydrophobic as curing time increases. ATR-FTIR and µRaman spectra reveal the absence of chemical interaction between GNPs and PDMS. The behavior of the PDMS real and imaginary parts of dielectric permittivity without and with GNPs and at increasing curing times seems to define the obtained GNPs/PDMS nanocomposites as low-loss materials. The obtained results show that the curing time significantly affects the filler distribution in the PDMS matrix and consequently the properties of the final nanocomposites. [ABSTRACT FROM AUTHOR]

LC‐circuit‐based resonant metamaterials (MM) operating in the terahertz (THz) are proven to detect the presence of nanoparticles within the capacitive gap of nanoantennas, manifesting a red‐shift in the resonance frequency. Sensitivity reduction (reduced red‐shift) due to the interaction/coupling of the substrate's Fabry–Pérot (FP) oscillations with the MM resonance is discussed. This new discovery of coupling is more probable and intense in thicker semiconductor substrates used in standard complementary metal‐oxide semiconductor processes, due to the high density of the FP oscillations and thus the probability for coupling with the single MM resonance increases. This also results in reducing the quality factor (Q‐Factor) of MM resonance, as well as the dielectric response to nanoparticles spread on the MM surface, by reducing the resonance frequency shift (ΔF) and thus the sensitivity of resonant MM. A sensitivity restoration of the MM resonance's red‐shift by decoupling it from the FP oscillations after thinning down the substrate by standard backside polishing is shown. The research is based on a combination of rigorous CST system‐level simulations along with THz impedance spectroscopy laboratory experiments: up to a fivefold enhancement of sensitivity of the thinned substrate compared with the conventional thick substrates is shown. This work has potential applications in the high‐sensitivity detection of nanomaterials and bio‐sensing at ultra‐low concentrations. [ABSTRACT FROM AUTHOR]

We show that CaCu 3 Ti 4 O 12 (CCTO) ceramics present either giant (>104) or moderate (∼102) dielectric permittivity ε' at room temperature (RT), depending on the grains resistivity. By sintering at 980 °C, a highly resistive bulk is obtained (resistivity of 5.8 GΩ cm) and no giant ε' is verified. A semiconducting phase develops into the grains by sintering at 1050 °C, with a remaining thin resistive phase, hence forming a core-shell bulk microstructure. By increasing the sintering temperature to 1100 °C, the semiconducting phase of the bulk grows at the expenditure of the insulating shell, forming the well-known Internal Barrier Layer Capacitance (IBLC) structure. It is therefore proved that the giant ε' in CCTO ceramics is linked to the grain boundaries dielectric response whose manifestation becomes resolved at RT when the bulk phase is semiconducting in nature. Such an effect is thermally originated during processing and related to Cu migration towards grain boundaries. [ABSTRACT FROM AUTHOR]

Different compositions of the nanocomposite lead-free multiferroic systems are fabricated by employing piezoelectric polyaniline (PANI) and magnetostrictive Ni0.5Co0.5Fe2O4 (NCF) by varying the NCF weight fraction. The current work reports the synthesis of xNCF:(1-x)PANI hybrid composite systems prepared via the physical blending method. X-ray powder diffraction (XRD) exhibits the presence of both; a polymeric amorphous phase of PANI (matrix) and a crystalline phase of inverse spinel ferrite NCF (filler) in the composites. The microstructure analysis along with the elemental composition of the samples are studied via Field emission scanning electron microscopy (FESEM) and Energy Dispersive X-ray Analysis (EDAX) respectively. Here, frequency-dependent dielectric permittivity exhibits percolation-type behavior where permittivity (ε′) attains a peak at a critical weight fraction (x = 0.3). The magnetic properties for the particular stoichiometric concentration (x = 0.3) of the composite exhibit a large enhancement in the saturation magnetization (Ms) of 75.22 emu g−1, while maintaining the soft ferromagnetism in the nanocomposite system. The switching behavior of electrical polarization in composite systems exhibits strong temperature dependence with a ferroelectric loop that appears to persist at even low temperatures (5 K). The remnant electrical polarization (Pr) is found to decrease with the increase in ferrite (NCF) concentration. Hence, the developed composite system at the high electric field exhibits both ferroelectric and ferromagnetic characteristics without significant conductive losses making it suitable for potential multiferroic and capacitor applications. [ABSTRACT FROM AUTHOR]

Relaxor ferroelectrics play an important role for technological applications, mainly for using in the fabrication of actuators, transducers and sensors. Therefore, there has been an increasing interest of the scientific community in the investigation of the physical properties of such system in order to better elucidate the observed intriguing and unsolved phenomena. In this work, relaxor Pb(Mg1/3Nb2/3)O3 (PMN) ceramic system was prepared and the dielectric properties have been studied in details as a function of frequency, temperature and magnitude of the DC-bias electric field. Results reveal that the temperature dependence of the dielectric permittivity can be successfully described in the whole analyzed temperature range (100–400 K) by using a macroscopic statistical model, which describe the dielectric response in relaxor systems with diffuse phase transition (DPT). By using this phenomenological model, the temperature and DC-bias electric field dependences of the dielectric permittivity have been also revisited, from the analysis of the DPT behavior, promoting a careful discussion on the nature of the phase transition in relaxors materials. The calculated sizes of the polar nanoregions (PNRs) suggest the development of a structural disorder in the studied system, which promote the high diffuse ferroelectric transition as the amplitude of the DC-bias electric field increases. [ABSTRACT FROM AUTHOR]

The demand to produce clean energy has been increasing over the last years due to the various climate changes, which are strongly afflicting the world. Therefore, it is necessary to implement new and alternative energy sources that contribute for the environment preservation. That is the case, for instance, of novel energy-storage devices, which could contribute for the current demand of clean energies. In fact, most of the system used nowadays are those lead-based materials, which are strongly pollutant and contribute for the environment contamination. In this way, the interest in the development and study of lead-free materials has become a real priority in the scientific community. The objective of the present work is to synthesize and investigate the physical properties of lead-free ferroelectric systems based on BaTiO3 (BT) with technological interest. In particular, the structural and dielectric properties have been investigated as a function of the Sn4+ content, used as a doping element in the BT hosting crystalline structure. The phase transition characteristics have been also analyzed in a wide temperature and frequency range. [ABSTRACT FROM AUTHOR]

Organic crystalline dielectric materials are attractive target in the field of materials chemistry. In their designing strategy, the molecular motion induced by the external dielectric field is required to maximize the polarization effect in the materials to realize a large dielectric constant. Especially, the molecular motion of curved-π aromatics such as C60 and their supramolecular complexes are the known to show characteristic smoothness in the solid state. In this context, we focused on the in-plane motion of the one of the representative buckybowl, sumanene (Sum) in its curve-to-curve-contacted columnar structure as the new platform of the motion for the emergence of dielectric response. The newly designed and synthesized fluorinated sumanene, 1,1-difluorosumanene (F2-Sum), which possesses two fluorine atoms on the same benzylic carbon of pristine sumanene showed a large dipole moment along the in-plane direction. Thermal analyses, variable temperature X-ray diffraction and IR measurements indicated the presence of in-plane motion of F2-Sum although no clear phase transition was involved. This thermal property of F2-Sum realized an anisotropic dielectric response with a Debye-type dielectric relaxation in the single crystalline state. Further trials to form the solid solution of Sum and F2-Sum in various mixing ratio realized the tuning of the dielectric property. [ABSTRACT FROM AUTHOR]

This paper reviews a procedure that allows for extracting primary photoelectron or Auger electron emissions from homogeneous isotropic samples. It is based on a quantitative dielectric description of the energy losses of swift electrons travelling nearby surfaces in presence of stationary positive charges. The theory behind the modeling of the electron energy losses, implemented in a freely available QUEELS-XPS software package, takes into account intrinsic and extrinsic effects affecting the electron transport. The procedure allows for interpretation of shake-up and multiplet structures on a quantitative basis. We outline the basic theory behind it and illustrate its capabilities with several case examples. Thus, we report on the angular dependence of the intrinsic and extrinsic Al 2s photoelectron emission from aluminum, the shake-up structure of the Ag 3d, Cu 2p, and Ce 3d photoelectron emission from silver, CuO and CeO2, respectively, and the quantification of the two-hole final states contributing to the L3M45M45 Auger electron emission of copper. These examples illustrate the procedure, that can be applied to any homogeneous isotropic material. [ABSTRACT FROM AUTHOR]

To gain high dielectric constant, polymer composites with 1D fillers are researched for energy storage. However, high leakage conduction from polymer/filler interface and filler interconnection can induce high dielectric loss. For high dielectric constant and low dielectric loss, in this work, we raised a strategy of morphological synergy of fillers (1D catenulate semi-conductive CuO nano-filler and 0D insulating alumina nano-particles) to fabricate polymer-based ternary composites. Instead of 0D CuO, 1D CuO nano-chains with the improved specific surface area were employed for high dielectric constant via polymer/CuO interface polarization. Spherical alpha-alumina nano-particles were used for reducing polymer/CuO interface leakage conduction and depressing CuO percolation to gain low dielectric loss. Compared with rather high dielectric constant and dielectric loss in polymer/CuO binary composites, moderately high dielectric constant and rather low dielectric loss were achieved in ternary composites. Via excellent synergy of CuO and alumina, ternary composites showed more promising dielectric properties. Ternary composite with 9 wt% CuO and 3 wt% alumina exhibited a high dielectric constant of ~ 64 and low dielectric loss of ~ 0.16 at 20 Hz. This work might pave a road for large-scale preparation of high-performance composite dielectrics by morphological synergy of fillers. [ABSTRACT FROM AUTHOR]

The complex dielectric permittivity of a sintered ceramic tablet consisting of 70.5% BiFeO3, 27.7% Bi2Fe4O9 and 1.8% Bi25FeO40 was analyzed as a function of temperature from – 120 °C to 230 °C in two separate temperature runs. The results reveal a complicated dielectric response with two temperature activated relaxation processes. The first is purely Arrhenius relaxation related to hopping processes between Fe3+ and Fe2+ traps induced by oxygen vacancies at grain boundaries. The second process is more unusual. Its characteristic relaxation time follows a quasi-Vogel–Tammann–Fulcher temperature behavior and from fitting the critical temperature point is estimated at T 0 = 766 K . It is absent in the second temperature run. It can be related to dynamic rearrangements of domain boundaries between different crystallites in the ceramic. The results also reveal a ferroelectric phase transition that decayed with repeated heating cycles of the tablet. The ferroelectric phase transition in pure BiFeO3 is 1098 K, whereas the current results show it at 373 K. The origin of this reduction in the critical temperature of the phase transition is traced to locally induced strains on grain boundaries mainly because of unit cell size mismatch between BiFeO3 and Bi2Fe4O9. [ABSTRACT FROM AUTHOR]

• ZnWO 4 microwave dielectric ceramics of the crystal structures, phase evolution, the dielectric response and the lattice vibrational characteristics sintered at different temperatures were studied. • The lattice vibrational characteristics sintered at different temperatures were analyzed utilizing Raman and infrared reflection spectroscopy. • The four-parameter semiquantum (FPSQ) model was utilized to fit and simulate the intrinsic dielectric properties of the ZWO ceramics. They were compared with the measured and theoretical values calculated by Clausius-Mossotti (C-M) and damping (γ) equations. • The relationship between the structure and properties of the ZnWO 4 ceramics sintered at different temperatures were elucidated through the use of Raman spectroscopy, overcoming the limitation of solely textual description without mathematical quantification. The study meticulously examined the impact of varying sintering temperatures on the phase transformations, crystallographic configurations, dielectric response mechanisms, and lattice vibrational characteristics of the ZnWO 4 ceramics. Far-infrared reflectance spectra were fitted using a four-parameter semiquantum model to obtain the intrinsic dielectric properties. Moreover, the contribution to the dielectric properties for each vibrational mode was analyzed, indicating that the lower-frequency mode had the most contribution. The relationship linking the structural aspects to the properties of ZnWO 4 ceramics was elucidated through an analysis of the Raman spectral modes across a range of sintering temperatures, overcoming the limitation of solely textual description without mathematical quantification. When sintered at 1070 °C, the ZnWO 4 ceramic had the best dielectric properties: ε r = 14.81, Q×f = 34,239 GHz (f = 9.69 GHz), with the highest relative density of 96.95 %. [ABSTRACT FROM AUTHOR]

This study presented the one-step synthesis of sulphur (S) and nitrogen (N) dual-doped graphene using atmospheric thermal plasma. The doped graphene was synthesized in the magnetically rotating arc plasma with CS 2 as the sulphur source, N 2 as the nitrogen source and CH 4 as the carbon source. At the same reaction temperature, the concentrations of S and N in S and N dual-doped graphene were higher than those in S/ N -doped graphene, which indicated that the dual-doped mode had a promoting effect on the doping level. In addition, increasing the input power effectively increased the doping levels of S and N atoms, which were up to 15.0 at% and 6.9 at%, respectively, at an input power of 19 kW. The S and N dual-doped graphene displayed excellent microwave absorption capability, with an optimal reflection loss of −56.4 dB at 16.3 GHz, and the effective absorption bandwidth reached 5.7 GHz when the doping levels of S and N atoms were 12.2 at% and 5.1 at%. This simple and rapid method for preparing S and N dual-doped graphene might facilitate the application of heteroatom doped graphene. [Display omitted] • S and n dual-doped graphene was synthesized through a one-step process using atmospheric thermal plasma. • The highest doping levels of elemental S and N were 15.0 at% and 6.9 at%, respectively. • The optimum RL at 16.3 GHz was −56.4 dB and the EAB reached 5.7 GHz. [ABSTRACT FROM AUTHOR]

Recent experiment reveals that the dielectric response to the bias electric field has obvious dependence on the frequency, which is mainly manifested in strong field-enhanced effect and weak field-enhanced effect, and reveals the novel mechanism behind this behavior. We find that the strong field-enhanced effect is caused by electromechanical coupling resonance originating from field-induced rearrangement. Considering inherent multiscale inhomogeneity, multiscale polar nanoregions distribute in the KTN crystal, and we find that the dielectric permittivity can be increased by enhanced vibration caused by the resonance between the multiscale PNRs and electric field, resulting in weak field-enhance effect. In addition, the multiscale inhomogeneity can also cause local nonmonotonic behavior of dielectric response to the electric field. Our finding provides a better understanding for the field-driven dynamics of the multiscale PNRs and paves the way to develop promising electro-optic devices, deflectors and tunable device. [ABSTRACT FROM AUTHOR]

In this paper, CaWO 4 - x wt. % LiF (x = 0.5–3.0) microwave dielectric ceramics are prepared by conventional solid-state reaction at 850 °C. All the X-ray diffraction peaks are attributed to CaWO 4 , combined with the results of X-ray photoelectron spectroscopy and scanning electron microscope. They indicate that LiF forms liquid phase at high temperature, exists in amorphous phase, and the CaWO 4 - x wt. % LiF samples belong to the composite ceramics. With the increase of the LiF content, the liquid phase fills the pores of the ceramics and increases the compactness. Therefore, the quality factor increases from 59,055 GHz (x = 0.5) to 77,855 GHz (x = 3.0), and the dielectric constant decreases from 9.26 (x = 0.5) to 8.41 (x = 3.0). The lattice vibration characteristics of the CaWO 4 - x wt. % LiF samples are studied by Raman and infrared spectroscopy. The external modes associated with the vibration of the Ca–O bonds have the greatest influence on the dielectric response, as shown by the fitting results based on the four-parameter semi-quantum (FPSQ) model. In addition, the simulated intrinsic properties and measured values are in general agreement. When the x value increases, the dielectric constant decreases with the decrease of the bond length. The quality factor has a negative correlation with the FWHM value of the B g mode and a positive correlation with the packing fraction. Finally, the CaWO 4 -3 wt.% LiF sample has good compatibility with the silver powders at 850 °C, and high application value in the LTCC field. [ABSTRACT FROM AUTHOR]

This article describes a novel research method for evaluating the aging state of the primary insulation material of large generator stator bars based on combining dielectric response methods with the entropy weight method. Vacuum pressure impregnation (VPI) epoxy-mica insulation specimens subjected to different electrical aging time periods were characterized via frequency domain spectroscopy (FDS), polarization and depolarization current (PDC), and thermal stimulated depolarization current (TSDC) tests. The comprehensive characteristic (VPI) parameters obtained by calculating the characteristic dielectric response parameters using the entropy weight method were used to describe the aging state of the VPI epoxy-mica insulation. The results show that during electrical aging, microcosmic structural variations within the insulation directly manifested as changes in the characteristic dielectric response parameters and indirectly affected the comprehensive evaluation parameters of the entropy weight method. [ABSTRACT FROM AUTHOR]

A series of double-perovskite La2Co1−zFezMnO6 (z = 0, 0.2–1.0) ceramics were synthesized using a well-established sol–gel method. The series of samples with a monoclinic phase and a P21/n symmetry were characterized by XRD, FTIR, conductivity, and capacitance measurement to extract charge-transport and dielectric characteristics at room temperature. The obtained IR spectra fitted well with the Lorentz oscillator model to calculate the damping factor, optical frequency, and oscillator strength and compared with the theory, which gave better agreement. The calculated activation energies from the Arrhenius plot supported the semiconducting nature of all samples. The temperature and frequency-dependent dielectric parameters, such as the real part ( ε r ′ ), imaginary part ( ε ″ ) of the dielectric constant, dielectric loss (tanδ), and ac-conductivity (σac) were extracted. The dielectric constant ( ε r ′ ,     ε ″ ) and dielectric loss (tanδ) were enhanced at a low frequency, while the ac-conductivity (σac) displayed higher values at higher frequencies. The enhancement in the dielectric parameters with increasing iron concentrations arose due to the higher surface volume fraction of iron (Fe3+) ions than the cobalt (Co3+) ions. The radius of the Fe3+ (0.645 Å) was relatively higher than the Co3+ ions (0.61 Å), significantly influenced by the grains and grain boundaries, and enhanced the barrier for charge mobility at the grain boundaries that play a vital role in space charge polarization. [ABSTRACT FROM AUTHOR]

Ferroelectrics (FEs) are increasingly used in nonvolatile memory applications. However, the impact of the electric dipole switching on its material parameters, in particular on the dielectric response, is not fully understood. In this work, an analytical model, linking the dielectric response to the potential energy curve, is first used to qualitatively illustrate the nonconstant evolution of the dielectric response with applied electric field. Increasing precision, we then show from first-principles density functional theory simulations that defect-free FE materials undergo changes in potential energy near the FE switching that lead to vibrational modes softening, which impacts the dielectric response. In particular, we observe that the dielectric response $\varepsilon $ of an FE material with antialigned polarization increases as the applied electric field increases toward the coercive field. We incorporate this new insight in the time-dependent NLS-based predictions and demonstrate that this evolution of the dielectric response right before polarization reversal is required for a proper match between experiment and prediction of the capacitance–voltage (CV) characteristics of the metal–ferroelectric–metal (MFM) capacitor. [ABSTRACT FROM AUTHOR]

A convenient chemical precipitation route was applied to prepare cupric oxide nanoparticles using copper acetate as precursor material. The influence of the reaction conditions on the formation of CuO nanoparticles was studied. The particle size of cupric oxide varies between 7.79 and 23.83 nm depending on the sodium hydroxide amount. The crystallite size of CuO nanoparticles obtained by electrospinning and calcination was of 42.25 nm. X-ray diffraction, scanning electron microscopy, EDX, XPS, electronic absorption and emission spectra were used to discuss the structural, morphological and optical properties of the CuO nanostructures. The electrical characteristics of CuO nanoparticles were investigated by dielectric and conductivity measurements. The dielectric constant (ε ′) and loss (ε ") were found to be decreased as the frequency increased. The photocatalytic activity of CuO nanoparticles was investigated following the degradation of ciprofloxacin. [ABSTRACT FROM AUTHOR]

In this study, we used Monte Carlo simulations to explore the dielectric properties of a graphene-type nanolattice, revealing significant effects on blocking temperature. The ferroelectric interaction and external electric field parameters greatly influence the nanolattice's dielectric and thermal properties. We observed a polarization plateau and multiple hysteresis loops, indicating stability and various polarization states. Unexpected ferroelectric behavior in graphene-based systems was confirmed experimentally in moiré heterostructures, validating theoretical predictions. This aligns with models like the Ising model and enhances material stability and response, offering insights for precise control over dielectric properties in nanotechnology. [ABSTRACT FROM AUTHOR]

Here, we report the composite effect of aluminum doping on the dielectric response of Diamond-Like Carbon (DLC) thin films. In addition, the contribution from preparation parameters like acetylene flow rate is also considered to understand sample behavior. AC conductivity study shows the existence of a nonlinear increase of conductivity with frequency leading toward the Jump Relaxation Model (JRM). The transition frequency (f t) is observed, which increases with conductivity. The study reveals that dielectric response is influenced by space charge conductivity, prompting us to adopt the modified Debye law. Deviation from ideal Debye behavior is also confirmed in dielectric modulus analysis. The deviation is frequency-dependent, and a higher deviation is observed in the high-frequency region. Plotting of the Master curve shows the presence of different relaxation dynamics in different samples. A current-voltage (I-V) study of different samples is also undertaken, showing higher values (greater than unity) of the ideality factor. [Display omitted] • AC conductivity increases with acetylene flow as well as with higher Al doping. • A very high value of dielectric permittivity is observed in present samples. • A single dielectric relaxation peak exists for samples with lower Al content. • The highest Al concentration shows double relaxation peaks. • The ideality factor is found to be greater than unity for all the samples. [ABSTRACT FROM AUTHOR]

• CeMn 1-x A x O 3 (A = Co, Ni and x = 0, 0.05, 0.10, 0.15) perovskite nanomaterials were synthesized using a modified polyacrylamide gel method. • The XPS analysis discloses that Mn has mixed oxidation states of Mn4+, Mn3+ and Mn2+, while Ni have oxidation states of Ni3+ and Ni2+, and Co has a Co3+ oxidation state. • The Co and Ni doped CeMnO 3 nanomaterial produced enhanced dielectric characteristics. • The Cole–Cole plot of doped CMO nanomaterial shows two semi-circle arcs, indicating the concurrent influence of both grains and grain boundaries. Nanostructured perovskite materials doped with transition metal ions have attracted significant attention due to their unique electronic and dielectric properties. In this study, we present the synthesis and thorough characterization of cobalt (Co) and nickel (Ni) ion-doped CeMnO 3 (CMO) perovskite nanoparticles using a modified polyacrylamide gel method. Our structural analysis suggests that the perovskite phase stabilizes with an orthorhombic phase (Pbnm space group). Morphological analysis conducted via field emission scanning electron microscopy (FESEM) unveils the formation of clustered nanospherical particles. X-ray photoelectron spectroscopy (XPS) reveals mixed oxidation states of Ce, Mn, and Ni ions. Furthermore, UV–Vis and photoluminescence spectra analyses demonstrate a distinctive reduction in band gap and suppressed charge carrier recombination upon doping. The substitution of Ni and Co ions also enhances the screening effect, reducing Coulombic interaction between photoexcited electrons and holes and subsequently increasing the dielectric constant. Analysis of the Cole-Cole plot demonstrates the augmentation of capacitance with Ni substitution. These findings collectively suggest that the decreased dielectric loss and enhanced dielectric constant support the feasibility of these materials for application in storage devices. [ABSTRACT FROM AUTHOR]

This paper proposes a rational approximation-based approach to find positive real parameters for the extended Debye model (EDM), aimed at condition assessment of insulation systems of power transformers. The EDM can model the slow and fast polarization phenomenon, including relaxation mechanisms with different relaxation times within a composite dielectric material. In the proposed approach, the complex permittivity of the transformer's composite insulation is approximated via rational functions, as given by the vector fitting (VF) software tool, and the EDM parameters are identified from the obtained poles/residues. To guarantee positive real parameters, i.e., a physically realizable circuit, VF is internally modified to calculate the final residues of the rational approximation via a constrained linear least-squares problem without resorting to further post-processing algorithms, as in existing methods, hence without affecting fitting accuracy. The effectiveness of the parametrized EDM is demonstrated in two ways: (a) by reconstructing frequency domain spectroscopy (FDS) curves provided via measurements in new oil-immersed power transformers and (b) by the comparison of the calculated polarization current given by EDM versus real measurements in time domain. The achieved fitting accuracy in most of the cases is above 99 percent for the reconstructed FDS curves, while the polarization current waveform is reproduced with good agreement. [ABSTRACT FROM AUTHOR]

Lead-free La0.02Ba0.97TiO3 (2LBT) ceramic was elaborated via the molten-salt method characterized by XRD and Raman spectroscopy. Further their electric, dielectric, and ferroelectric properties were investigated. XRD results demonstrate that the sample possessed a pure-tetragonal structure with a space group of P4/mmm. The notable effect of incorporating the La3+ cation into an A-site sublattice was clarified using Raman spectroscopy. Significant improvements have been demonstrated in dielectric properties. The observed relaxation is attributed to Maxwell–Wagner polarization. 2LBT sample demonstrated a 3 phase transition with negligible frequency dispersion indicating diffuse phase transition at the specific temperature range (292–700 K). Upper than 700 K, 2LBT sample provided a pointy transition. The electrical properties obtained from the complex electric modulus reveal a conduction process owing to the short-range mobility of charge carrier. Both ac and dc electrical conductivities are considered vs. frequency and temperature. [ABSTRACT FROM AUTHOR]

Dielectric response measurement is widely used to characterize oil/oil-impregnated pressboards in order to evaluate the condition of transformer insulation. Insulation systems with oil can exhibit voltage dependence at low frequencies. This is due to the limited number of mobile charges in the liquid, rather than to the dielectric relaxation processes that may, in some cases, be of more interest to study. This work investigates the voltage-dependent properties of oil/oil-impregnated pressboards under ac voltages with regard to the complex permittivities. Frequency-domain spectroscopy (FDS) measurements are made with a dc voltage added to the ac voltage stimulus. Considered influences are the voltage amplitudes and polarity as well as the dependence on temperature. Properties of the space-charge polarization in the oil and oil-impregnated pressboard are calculated and discussed based on the dc-biased measurements. It is seen that using the dc bias in the FDS measurements of oil/oil-impregnated pressboard can significantly decrease the voltage dependence of the results that are caused by ion drift and consequent depletion of ions from the bulk liquid. Based on the dc-biased measurements, the complex permittivity due to the linear and nonlinear polarization can be separated. [ABSTRACT FROM AUTHOR]

In this work, we studied the nature of repolarization processes in KNN-0.05Ta ceramics in the temperature range of structural phase transition. We have found the anomalous behavior of reverse dependences ε'(Ε=), while measuring the response in weak ac-fields in the sample exposed to the constant bias field. Behavior of ε'(Ε=) was compared with the polarization loops measured in sinusoidal fields of various amplitudes. [ABSTRACT FROM AUTHOR]

In this work, novel double perovskites RBaFeTiO 6 (R = Pr, Nd) have been prepared through the sol-gel process. The structural, morphological, spectral, and dielectric behaviors were investigated by X-ray diffraction (XRD), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), Raman spectroscopy, Fourier transform infrared (FTIR) spectroscopy, dielectric measurements, and impedance spectroscopy. The objective of this work is to study these properties and investigate the effect of rare earth cations. XRD analysis confirmed the disordered cubic double perovskite structure of all prepared samples. The lattice parameters, bond lengths, and bond angles determined from the Rietveld refinement analysis are found to be dependent on the R3+ cation size. SEM and TEM micrographs indicated an irregular size distribution of the grains forming these double perovskites. The elemental composition and the stoichiometry of the prepared samples were verified by energy-dispersive X-ray spectrometer (EDX) elemental mapping. Raman and infrared spectroscopies have affirmed the influence of the rare earth element on vibrational properties and bond lengths. The dielectric properties were studied as a function of frequency. Electrical conduction follows Jonscher's universal power law and the conduction is attributed to the localized relaxation (reorientational) hopping mechanism. The presence of both negative (NTCR) and positive (PTCR) temperature coefficients of resistance in these materials is also affirmed by impedance spectroscopy. [ABSTRACT FROM AUTHOR]

Employing a modified sol-gel combustion technique, BiFeO 3 and Bi 0.85 Ba 0.15 Fe 1-x Al x O 3 (x = 0, 0.025 and 0.050) nanoparticles were synthesized, and the effects of these dopants were investigated analyzing the experimental findings and adopting the DFT + U approach. Rietveld analysis of XRD revealed a deformed perovskite rhombohedral structure for all the Ba–Al co-doped nanoparticles, which was also validated by theoretical study. Suppression of the low-frequency dispersion promoting outstanding dielectric stability was observed due to Al3+ doping, and the least dielectric constant along with the highest resistivity was reported for BBFAO-2.5. The band gap of co-doped nanoparticles (x = 2.5 & 5) decreased to 1.95 eV and 1.98 eV, respectively, compared to 2.06 eV, and 2.09 eV for BBFAO-0 and pure BFO. The average particle size of all the co-doped nanoparticles was below the repeat length of the cycloid structure, which is favorable for improved magnetic properties. Remanent magnetization, coercivity, and squareness increased as the motion of domain walls is inhibited by the smaller-sized nanoparticles. DFT + U study further endorses the findings of the experimental study. Analysis of DOS revealed the emergence of shallow impurity states around VBM due to doping, which can operate as active trap centers and impede carrier recombination. Thus, it can be inferred that, Ba–Al co-doped nanoceramics with intriguing dielectric, optical, and magnetic properties are a promising candidate for high-frequency microwave devices, magnetic memory and storage devices, near UV-detector, and solar photocatalysis applications. [ABSTRACT FROM AUTHOR]

The frequency-dependent dielectric responses of non-uniformly dispersed porous carbon fiber/mullite composites fabricated by gel-casting are intensively investigated in the X-band range. Experimental data have shown the frequency dependence of dielectric permittivity and electrical conductivity of the overall composite. The dielectric responses of non-uniformly dispersed porous carbon fiber/mullite composites in X-band are quantitatively modeled through a multi-scale homogenization method based on the effective-medium approximation. The non-uniform dispersion of carbon fibers and micro-pores in the mullite ceramic has been included via a corresponding multi-scale geometric setting. The effective dielectric permittivity and electrical conductivity of the composite both enhance with the fiber volume concentration. It is demonstrated that the decreasing dielectric permittivity and increasing electrical conductivity with respect to the AC frequency can be attributed to frequency-dependent dielectric relaxation and electron hopping effects at the interface. Furthermore, improving the uniform dispersion of carbon fibers in the mullite is essential to achieve the enhanced dielectric response of porous carbon fiber/mullite composites. The present paper can provide the directions to design the porous carbon fiber/mullite composites for micro-electronic devices in the high-temperature environment. [ABSTRACT FROM AUTHOR]

The dielectric response of magnetic alkali borosilicate glasses containing single-domain magnetite nanoparticles was studied upon heating and cooling in magnetic fields from 0 to 10 Т in the temperature range from 5 to 100 K in the frequency range from 1 Hz to 160 kHz. An anomaly of the dielectric response was observed for the single-domain nanoparticles of magnetite in the temperature range of 15–50 K, position of which corresponds to the transition into the relaxor state observed in bulk material. A temperature hysteresis of this anomaly was found upon heating and cooling, which decreased as the observation frequency decreased. [ABSTRACT FROM AUTHOR]

Aurivillius phase Bi5CrxFe1−xTi3O15 (0≤ x ≤1) thin films are prepared by the chemical solution deposition method, and the effect of Cr content on the microstructure, ferroelectric property, and electric transport behavior of Bi5CrxFe1−xTi3O15 films is investigated. X‐ray diffraction analysis shows that all of Bi5CrxFe1−xTi3O15 films are complete solid solution and maintain the Aurivillius structure. The replacement of Fe3+ with smaller Cr3+ decreases anisotropy and lattice aspect ratio in a‐b plane, which is minimized at the composition of Bi5Cr0.5Fe0.5Ti3O15. This changes the grain shape from sphere to plate, and Bi5Cr0.5Fe0.5Ti3O15 film consists of only plate‐like grains. Cr doping increases saturated polarization (Pm) and decreases coercive field (Ec). Cr doping increases Pm of Bi5CrxFe1−xTi3O15 film to 35 μC/cm2, but decreases Ec down to 125 kV/cm. A decrease in the lattice aspect ratio of a‐b plane promotes the alignment of ferroelectric dipoles under electric field. The frequency‐dependent dielectric property and the leakage current show that the plate‐like grains of Cr‐rich Bi5CrxFe1−xTi3O15 films suppress the transport of carriers from grains to grains and prevents a dramatic leakage current increase. The results of this study provide a design rule to control the ferroelectricity of Aurivillius phase Bi5CrxFe1−xTi3O15 thin films by modifying the composition and lattice aspect ratio. [ABSTRACT FROM AUTHOR]

Dielectric response and charge decay test are widely used for evaluating the electric properties of the insulation pressboards in the converter transformer. In this paper, Frequency Domain Spectroscopy (FDS) test, breakdown test, and charge decay characteristics experiments are carried out on the cellulose pressboards modified by TiO 2 with different mass fractions and diameters. The FDS of the modified cellulose pressboards at ambient temperature is measured from 0.0001 to 1000 Hz by IDAX 300. The process is conducted at the laboratory to study the characteristics parameters of the dielectric response behaviors, such as complex relative permittivity. The results show that the values of the relative permittivity for the insulation pressboards modified by TiO 2 (5 wt%, 10 nm) are reduced. To verify the accurate results, the microstructures of the pressboards modified by 5 wt% with 10 nm diameter are observed by a Scanning Electron Microscope (SEM). The breakdown strength tests are carried on the samples modified by 1 wt%, 3 wt%, 5 wt%, 7 wt% with 10 nm TiO 2 under the intensity electric and high-temperature field, respectively. The values of the breakdown strength are increased by 38% and 11.5% for single layer samples and oil/pressboard composite insulation models modified by 5 wt% nano-TiO 2 filler. In addition, the charge decay characteristics are tested on the samples. The proper proportion additions can reduce the trap density. [ABSTRACT FROM AUTHOR]

Poly(3,4-ethylenedioxythio-phene):poly(styrenesulphonate) (PEDOT:PSS) nanofibres were first prepared via electrospinning method. Microstructural arrangement of the nanofibres was investigated by scanning electron microscopy technique. Then, the effect of beta irradiation with different absorbed doses on their impedance spectra were investigated in the frequency range from 5 to 13 × 106. It was observed that beta irradiation leads to a considerable decrease in both real and imaginary parts of the complex dielectric function, and alternating current conductivity of the nanofibres. The obtained frequency dependent conductivity data were discussed in terms of pair approximation. It was established that, for all beta irradiation doses, the frequency dependence of the conductivity is characterized by the presence of four frequency regions with different slopes. Analysis of the impedance data revealed that chain scission via chain cross-linking and free radical formation are most likely mechanisms for changes in impedance parameters. Two clear semicircles in Nyquist plot have been successfully explained by employing two parallel R-CPE equivalent circuits in series configuration. An overall evaluation of the obtained data indicates that electrospun PEDOT:PSS nanofibres have great potential for the development of highly sensitive impedance-based beta radiation sensor. [ABSTRACT FROM AUTHOR]

Capacitors in electrical and electronic systems composed of thin film dielectrics operate under extremely high electric fields. Dynamics of charge transport and relaxation are closely correlated to the energy storage properties and electrical degradation of thin film dielectrics for capacitive applications. In this paper, the dielectric relaxation properties of poly (vinylidene fluoride-hexafluoropropylene) (P(VDF-HFP)) copolymer films are investigated over a broad frequency range from 10 mHz to 10 MHz and temperature range from −130 °C to 130 °C. The dielectric responses correlated to bulk and interfacial processes are clarified by varying the thickness and interfacial contact status of P(VDF-HFP) films. A low frequency process originating from the quasi-DC (QDC) process and a dielectric dispersion process correlated to the interfacial polarization are identified based on the Dissado-Hill dielectric response model and the equivalent circuit analysis. The high permittivity and high operation electric field of P(VDF-HFP) for capacitive energy storage give rise to improved blocking capacitance associated with the interface, suggesting the enhanced interfacial polarization. This work provides insights into the bulk and interface charge dynamics of polymer thin film dielectrics. [ABSTRACT FROM AUTHOR]

Results of studies of dielectric response and polarization in PbCo1/3Ta2/3O3 (PCT) single crystals grown by spontaneous crystallization are presented. Anomalies in the temperature dependence of the complex dielectric permittivity at 350, 270, 183, and 105 K have been observed. Using the thermally stimulated depolarization method, the temperature region of remnant polarization existence has been revealed below 270 K. It is assumed that in PCT, as well as in PbCo1/3Nb2/3O3 (PCN), in low-temperature region the phase separation caused by continuous switching of charge (valence) of Co2+/Co3+ and Ta4+/Ta5+ ions is realized. [ABSTRACT FROM AUTHOR]

Dielectric properties of compositionally-graded barium strontium titanate (BST) thin films respectively on Ti and stainless steel (SS) plates were computed using a modified thermodynamic model. Calculated results predict that higher dielectric constant and tunability can be obtained when the films are onto Ti substrates, which have smaller thermal expansion coefficient (TEC). For Ti substrates, "up-graded" films (Ba/Sr ratio increases from substrate to surface) exhibit higher tunability than "down-graded" films; whereas "up-graded" films on SS plates have relatively lower tunability. The received larger dielectric constant and tunability are because of smaller total out-of-plane polarization, which is resulting from smaller total compressive strain. The calculated dielectric constant and tunability of such graded films are in accordance with those of the films fabricated via sol-gel approaches, indicating that the dielectric behavior of ferroelectric films can be adjusted by designing compositional gradient. [ABSTRACT FROM AUTHOR]

The main representative of the tetragonal tungsten bronze family, strontium barium niobate, has been recently studied by the scattering and spectroscopic techniques [diffuse scattering (DS), Raman, infrared, and high-frequency dielectric spectroscopies] to decipher the nature of its ferroelectric-relaxor transformation tuned by composition. DS revealed that mesoscopic range ordered correlations along the polar axis are presented in the crystal, being less organized in the relaxor compositions with higher Sr content. For these compositions, transverse polar correlations are found to be anisotropic. Pair distribution function experiments and first-principle calculations in several compositions showed a concomitant new peak around ~6.5 Å, which develops on cooling and cannot be explained by the current structural models with long-range incommensurate oxygen tilts but with a short-range ordered tilt arrangement. This relates with the development of the macroscopic polarization, tightly linked to the structure, and shows two different contributions related to the two different crystallographic sites for the ferroactive Nb atom, recalling a picture of two independent polarization networks showing disparate dynamics, temperature behavior, and correlation lengths. Cationic substitution in different channels affects mainly the relaxations. Above the MHz range, all members of the solid solutions show three main relaxations, whose temperature dependence is unalike, due to the distinct correlation lengths and nature of the processes. On increasing Sr content, the frequencies are higher, and the contribution to the permittivity of excitations at GHz–THz ranges gets stronger. A soft anharmonic central mode at THz range is the characteristic for all the compositions, together with the slowing down of a relaxation at GHz–MHz ranges, revealing the coexistence of displacive and order–disorder mechanisms of the ferroelectric phase transition in these solid solutions. [ABSTRACT FROM AUTHOR]

Here, based on the dielectric response analysis, we report the charge transport dynamics as related to space charge accumulation for three model XLPE composites with 2D platelet silicate fillers. Dynamics of charge transport and the interplay between polarization and space charge are revealed by the equivalent circuit analysis with the Dissado-Hill dielectric response model. In addition to the quasi-DC process, a characteristic dielectric loss peak in the frequency range of 0.1 Hz to the power frequency is observed and attributed to the relaxation of charges trapped by filler-polymer interfaces. It is demonstrated that the physical nature of trapping and transport revealed by parameters extracted from the quasi-DC process and dielectric loss peak can be well correlated to the characteristics of space charge accumulations in the model XLPE composites containing distinctively different 2D platelet fillers. [ABSTRACT FROM AUTHOR]

Thermoresponsive dielectric materials have attracted the interest of researchers as they exhibit very important application prospects in stimuli-responsive smart devices. In this contribution polyethylene glycol (PEG), impregnated in halloysite nanotubes (HNTs), was incorporated into poly(vinylidene fluoride) (PVDF) for tailoring the thermoresponsive dielectric properties based on a non-ferroelectric phase transition. The PVDF/PEG/HNTs displayed a remarkable rise of dielectric constant between 20 and 30 °C. The mechanism is related to the enhanced orientational polarization effect triggered by the solid–liquid phase transition of the PEG. This make it possible to design stimuli-responsive smart materials through a simple, low-cost and efficient strategy. The present work provides an alternative and innovative routine for tailoring thermal-induced dielectric behaviors via a non-ferroelectric phase transition by introducing PEG into a high-dielectric-constant polymer matrix. [ABSTRACT FROM AUTHOR]

This work studies the impact of silica nanoparticles on the dielectric properties of synthetic ester oil. A stable nanofluid is prepared by addition of surfactant. With addition of nanoparticles there is an increment in dielectric constant and decrement in dielectric loss constant. An attempt is made to understand the conduction mechanisms in uniform field and non-uniform electric field configuration by means of analysing the mobility of ions. Under uniform electric field stress (<0.1 kV/mm), by means of conduction current measurement with polarity reversal, the ionic mobility, conductivity, ionic concentration and ionic radius are deduced. There is a reduction in ionic mobility by addition of nanoparticle and surfactant. To understand the conduction mechanisms in high electric field condition, the current-voltage characteristics of the nanofluid are measured. Using this data, apparent mobility due to electrohydrodynamic motion is estimated, giving a lower mobility in the case of nanofluid, which could be the cause of the increased corona inception voltage. [ABSTRACT FROM AUTHOR]

We show that powders of bismuth titanate, copper oxide, and titanium oxide can be transformed into a single Bi 2/3 Cu 3 Ti 4 O 12 phase and subsequently flash sintered at furnace temperatures of 855−910 °C in a single running experiment, with an electric field ranging from 5 to 15 V cm–1 and a current limit of 53 mA mm–2. The (di)electrical properties of the flashed materials were assessed by impedance spectroscopy. These ceramics show a giant dielectric constant (ε′ > 104), and an increasing resistivity with raising the field used in the flash, reaching a value as high as 6.7 MΩ cm for 15 V cm–1. Thus, the one-step experiment process described here greatly simplifies the fabrication of high-density single-phase ceramics of this material while at the same time improving its properties for low leakage high dielectric applications. [ABSTRACT FROM AUTHOR]

The response of polar solvents to ions and polar molecules dictates many fundamental molecular processes. To understand such electrostatically-driven solvation processes, one ideally would probe the dielectric response of a solvent to an idealized point test charge or dipole solute, as envisioned in classic continuum treatments of the problem. However, this is difficult in simulations using standard atomically-detailed solvent models with embedded point charges due to possible overlap with the test charge that lead to singular interaction energies. This problem is traditionally avoided for a realistic charged solute by introducing an excluded volume core that shields its embedded point charge or dipole from the charges in the solvent. However, this core introduces additional molecular-scale perturbations of the solvent density that complicate the interpretation of solvent dielectric response. In this work, we avoid these complications through the use of Gaussian-smoothed test charges and dipoles. Gaussian charges and dipoles can be readily inserted anywhere into an atomistic solvent model without encountering infinite energies. If the Gaussian-smoothing is on the scale of molecular correlations in the solvent, both the thermodynamic and dynamic solvation response is linear. Using this observation, we construct accurate predictive theories for solvation free energies and solvation dynamics for insertion of Gaussian charges and dipoles in polar solvents and demonstrate the accuracy of the theories for a widely-used model of water. Our results suggest that Gaussian test charge distributions can be used as an informative probe of dielectric response in molecular models, and our theories can be used to analytically predict the largest component of solvation free energies of charged and polar solutes. [ABSTRACT FROM AUTHOR]

The dielectric nature of polar liquids underpins much of their ability to act as useful solvents, but its description is complicated by the long-ranged nature of dipolar interactions. This is particularly pronounced under the periodic boundary conditions commonly used in molecular simulations. In this article, the dielectric properties of a water model whose intermolecular electrostatic interactions are entirely short-ranged are investigated. This is done within the framework of local molecular-field theory (LMFT), which provides a well-controlled mean-field treatment of long-ranged electrostatics. This short-ranged model gives a remarkably good performance on a number of counts, and its apparent shortcomings are readily accounted for. These results not only lend support to LMFT as an approach for understanding solvation behavior, but also are relevant to those developing interaction potentials based on local descriptions of liquid structure. [ABSTRACT FROM AUTHOR]