Analysis Of Dielectric Response Research Articles

A brilliant equation and dipole-relaxation dynamics in tuned BiFeO3−BaTiO3−MgFe2O4 triphasic composites mediated using spinel phase contents

The integration of perovskite and spinel materials into multifunctional composites offers diverse technological applications due to their unique properties. This study explores the detailed multifunctional characteristics of tri-phasic composites with general formula (1−x)(0.6BiFeO3 + 0.4BaTiO3) + xMgFe2O4 (0 ≤ x ≤ 0.1), synthesized using a straightforward two-step process. X-ray diffraction confirmed the high crystallinity and phase purity of the composites. Subsequent observations using field emission scanning electron microscopy revealed a highly porous morphology with varying grain sizes. Electrically, the composite with x = 0.08 exhibited notable dielectric impedance, and modulus characteristics, aligning well with the requirements for efficient energy storage. Magnetically, the material displayed a gradual reduction in coercivity values, reaching 199.59 Oe at x = 0.10, alongside a peak magnetization of 5.140 emu/g and a remanent magnetization-to-saturation magnetization (Mr/Ms) ratio of 0.173. These features underscore the material’s potential for magnetic memory applications. Detailed dielectric response analysis across wide frequency range highlighted suitability of as synthesized composites for advanced energy storage devices.

Fractal Analysis of Time Domain Dielectric Response to Reduce Complexity of Insulation Condition Diagnosis Methodology

Fractal Analysis of Time Domain Dielectric Response to Reduce Complexity of Insulation Condition Diagnosis Methodology

Dielectric response characteristics and moisture exposure evaluation of oil-paper insulation based on microstrip ring resonator

Moisture ingress significantly accelerates the aging of oil-paper insulated equipment, making accurate assessment of moisture content critical for the operation and maintenance of oil-immersed insulated power equipment. In this paper, a novel method for rapid moisture content evaluation is proposed based on a microstrip ring resonator (MRR) designed with a fundamental frequency of 1.16 GHz. A calculation model for the dielectric response analysis using MRR is established to characterize dielectric properties of the material layered on the substrate. ANSYS HFSS electromagnetic simulation software was used to study the impact of dielectric material thickness and the substrate on the MRR test results. Experimental measurement demonstrated that the maximum deviation in resonance frequency was merely 0.542 %. The dielectric properties of uniformly and non-uniformly damp insulating pressboard were analyzed across the frequency band from 1 to 6 GHz. The MRR test results were compared with those of the standard resonant cavity method and frequency domain dielectric spectroscopy (FDS) test. Using the regression algorithm and curve analysis, moisture assessment models for both uniformly and non-uniformly damp oil-paper insulation were established. The experimental results show that the MRR test can clearly distinguish between the pressboard samples with varying moisture levels under uniform conditions, with a maximum moisture evaluation error of 8.19 %. The results demonstrate that the MRR test method, requiring only 56 s, can quickly and effectively evaluate the moisture content of insulating pressboard.

Residual LSTM-based short duration forecasting of polarization current for effective assessment of transformers insulation

The empirical application of polarization and depolarization current (PDC) measurement of transformers facilitates the extraction of critical insulation-sensitive parameters. This technique, rooted in time-domain dielectric response analysis, forms the bedrock for parameterization and insulation modeling. However, the inherently time-consuming nature of polarization current measurements renders them susceptible to data corruption. This article explores deep-learning-based short-duration techniques for forecasting polarization current to address this limitation. By incorporating spatial shortcuts, the residual long short-term memory (LSTM) network facilitates the seamless propagation of spatial and temporal gradients. Furthermore, the relative forecasting assessment of the proposed residual LSTM model’s performance is made against traditional LSTM, attention LSTM, gated recurrent units (GRU), and convolutional neural network (CNN) models. Thus, optimal model selection strategies are evaluated based on their capability to capture extended dependencies and short-term information present in the data. In addition, the Monte Carlo dropout prediction is employed to estimate uncertainty in polarization current forecasts. The findings demonstrate that the proposed residual LSTM network model for polarization current forecasting yields the lowest error metrics and maintains prediction consistency over the testing duration. Thus, the proposed approach significantly reduces PDC measurement time, providing an effective means to develop proactive maintenance strategies for evaluating the insulation condition of transformers.

The Domain and Structural Characteristics of Ferroelectric Copolymers Based on Vinylidene Fluoride Copolymer with Tetrafluoroethylene Composition (94/6).

This paper presents data on the macroscopic polarization of copolymer films of vinylidene fluoride with tetrafluoroethylene obtained with a modified apparatus assembled according to the Sawyer-Tower Circuit. The kinetics of the polarization process were analyzed taking into consideration the contributions of both bound and quasi-free (impurity) charges. It was shown that an "abnormal" decrease in conductivity was observed in fields near the coercive fields. This could be associated with the appearance of deep traps of the impurity charge carriers formed by the polar planes of β-phase crystals. The conductivity data obtained from the charge and current responses differed. It was concluded that chain segments contributing to polarization with sufficiently low fields were present in the amorphous phase. A comparison showed that the average size of β-phase crystals (crystals of X-ray diffraction reflection width) was almost one order of magnitude lower than the domain size obtained using piezoresponse force microscopy (PFM). The analysis of the fast-stage dielectric response before and after polarization indicated that as the external polarizing field increased in the ferroelectric polymer chains, conformational transitions occurred according to the T3GT3G- → (-TT-)n и TGTG → (-TT-)n types. This was accompanied by an increase in the effective dipole moment in the amorphous phase chains. The analysis of the IR spectroscopy data obtained in transmission and ATR modes revealed a difference in the conformational states of the chains in the core and surface parts of the film.

Temperature Dependency of Ion Mobility in Synthetic Ester by Dielectric Response Analysis in Time and Frequency Domain

Synthetic ester is a promising alternative to mineral oil for emerging applications relying on high-power static conversion, such as solid-state transformers (SST). The highly compact components used in SSTs must fulfill MV-DC insulation requirements to guarantee the safe operation of the system, therefore, their design relies on the characterization of the dielectric stress caused by the electric field. The prediction of the electric field induced by DC voltages requires analyzing the conduction phenomena in the liquid, including the effect of charge transport due to ion drift. In this scenario, one of the critical parameters that determine the transport of charge and the resulting electric field distribution is the mobility of ions μ; the value of μ in synthetic ester is available only at room temperature, however, investigations on other dielectric liquids indicate a significant temperature dependency, which therefore needs to be characterized. In this paper, the temperature dependency of μ in synthetic ester liquid is determined by comparing alternative methodologies based on the analysis of the dielectric response in the time and frequency domain, and the viscosity of the fluid. The characteristics obtained by these methodologies are consistent; the temperature dependency of μ obeys the Arrhenius law and an increase of one order of magnitude starting from 1.1 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">–10</sup> m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> /Vs is observed in the 303K–353K temperature range.

A Decisive Study on Dielectric Response of Bi&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;O&amp;lt;sub&amp;gt;3&amp;lt;/sub&amp;gt;/Polystyrene &amp;amp; Bi&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;O&amp;lt;sub&amp;gt;3&amp;lt;/sub&amp;gt;/PVDF Composite as Flexible Electrodes for Energy Storage

In this manuscript a comparative study on Bi2O3/polystyrene and Bi2O3/PVDF composites has been executed via analysis of structural, bonding, surface morphology and dielectric response of composites for energy storage. The composites have been synthesized using solution cast method by varying concentrations of Bi2O3 (BO = 1 - 5 mw%) into polystyrene (PS) and polyvinylidene fluoride (PVDF) polymers respectively. X-ray diffraction confirms the generation of crystallinity, Fourier transform infrared (FT-IR) spectroscopy confirms bonding behavior and scanning electron microscopy (SEM) confirms uniform distribution of Bi2O3 (BO) in PS and PVDF polymers. Impedance spectroscopy has been employed for determination of dielectric response of the fabricated composites. The dielectric constant has been found to be increased as 1.4 times of pristine PS to BO5%PS95% composites and 1.8 times of pristine PVDF to BO5%PVDF95% composites respectively. These high dielectric composite electrodes are useful for flexible energy storage devices.

Time-domain signal analysis of dielectric response of nonlinear SDBD thruster in near space

The nonlinear time domain response signals of surface dielectric barrier discharge (SDBD) are the basis for studying the energy loss of SDBD thruster. This paper is based on the construction of a double layer lumped parameter circuit model in solid dielectric and discharge plasma regions; based on virtual instrument technology, a test device for AC dielectric characteristics of a nonlinear SDBD thruster was built to obtain the time domain signals of AC voltage and response current. According to the characteristic spectral curve of the voltage and the response current signal in the time domain, the response current is decomposed into resistive current (conduction current) and capacitive current (relaxation current) by an appropriate algorithm. The experimental results show that the response current in the discharge plasma region is mainly the capacitive current, and the peak capacitive current is about 2.9 times of the peak resistance current; Relaxation planned loss is the main form of energy loss in the discharge plasma region. Due to space charge limiting current effect and space charge saturation effect, the static and dynamic resistance of discharge plasma region have platform area and negative resistance characteristics respectively; Both static and dynamic capacitance have negative capacitor characteristics.

Ultralow dielectric loss in Tb + Ta‐modified TiO2 giant dielectric ceramics via designing defect chemistry

AbstractThe environment‐friendly materials exhibiting colossal permittivity play an increasingly important role in the electronics industry. In this work, (Tb0.5Ta0.5)xTi1−xO2 (x = 0, 0.005, 0.01, 0.02, and 0.04) ceramics with new defect clusters were fabricated to enhance the dielectric response. Significantly, all ceramic samples exhibit large dielectric constants (εr &gt; 104), whereas the ceramic with x = 0.005 exhibits an ultralow loss (tan δ) of about 0.008 at room temperature and 1 kHz. The origins of its excellent dielectric properties were revealed by XRD, X‐ray photoelectron spectroscopy, and dielectric response analysis, which were mainly caused by defective dipoles associated with oxygen vacancies (). These defective dipoles limiting the long‐range hopping of electrons lead to the electron pinning effect. Additionally, the frequency spectrum under DC bias and conductivity behavior suggests that grain boundary and electrode effects also contribute to the dielectric constant. This study not only explores the dielectric response properties of a new giant dielectric (Tb0.5Ta0.5)xTi1−xO2 ceramics but also offers a candidate material suitable for ceramics capacitors.

Colossal dielectric response and complex impedance analysis of LaFeO3 ceramics

The present investigations mainly focused on the colossal dielectric response and complex impedance analysis of LaFeO3 ceramics. The studied sample was prepared by a citrate gel method. Structural and microstructural properties are analyzed from the XRD pattern and SEM micrograph. The anomalies in the dielectric constant versus temperature plots are analyzed on the basis of polarization induced by the Maxwell-Wagner mechanisms and ferromagnetic interaction between the Fe[Formula: see text] ions driven by the oxygen vacancy mediated Fe[Formula: see text]–V[Formula: see text] –Fe[Formula: see text] exchange interaction A giant dielectric permittivity in the order of [Formula: see text]105 was observed in the sample even at the room temperature for 100 Hz. The colossal dielectric constant in LaFeO3 is mainly driven by the internal barrier layer capacitor (IBLC) formation. The formation of IBLC was explained on the basis of highly insulating grain boundary and less resistive/semiconducting grain, which was confirmed from both the resistance and capacitance of grain and grain boundary from the impedance analysis. The non-Debye-type relaxation process associated with the grain and grain boundary effect was investigated from the broad and asymmetric relaxation peak. The relaxation time for both the grain and grain boundary effect was also calculated. In addition to this, we have also analyzed the normalized bode plot of imaginary part of impedance and electrical modulus which suggests the relaxation process dominated by the short-range movement of charge carriers.

Interfacial polarization suppression of P(VDF-HFP) film through 2D montmorillonite nanosheets coating

Polymer based dielectrics with excellent high electric field withstanding capability are of great significance for enhancing the power density and payload efficiency for both electrical and electronic systems. However, polymer-metal interface is prone to defect formation, leading to the dielectric aging and the initialization of electrical breakdown failure. A facile Montmorillonite (MMT) coating is self-co-assembled on the surface of P(VDF-HFP) high-k film to form hundreds of 2D nanosheets layers to impede the charge injection over the metal-polymer interface. The MMT coating increases the breakdown strength of the P(VDF-HFP) co-polymer film from 405 to 452 MV/m. The high field conduction study reveals a highly enhanced Schottky injection barrier that blocks the charge injection from electrodes to polymer bulk, leading to significantly suppressed charge injection and conduction loss in polymer. In addition, the introduction of MMT layered coating leads to prominent suppression of interfacial polarization loss, a phenomenon known as the blocking capacitance, which would otherwise stem from the accumulated charges of polymer-metal interface, by one order of magnitude, as demonstrated by the dielectric response analysis by using the Dissado-Hill model over a broad range of temperature and frequency. The superior charge injection and interfacial polarization suppression via the application of MMT coating impart the P(VDF-HFP) co-polymer film with higher breakdown strength, and provides an effective approach to develop high performance polymer dielectrics by interfacial engineering. This work provides insights into the understanding of the enhancement mechanism of 2D coating.

Temperature Distribution in the Insulation System of Condenser-Type HV Bushing—Its Effect on Dielectric Response in the Frequency Domain

HV bushings are an important part of the equipment of large power transformers, responsible for their many serious (including catastrophic) failures. Their proper exploitation needs to apply correct and reliable diagnostics, e.g., the use of dielectric response methods, that take into account their specific construction and working conditions. In this article, based on laboratory tests carried out on a real bushing, it has been shown that the significant temperature distribution within its core significantly affects the shape of the dielectric response of its insulation; therefore, the approach to its modeling should be changed. Hence, a new method for interpreting the results, using the so-called the 2XY model, is proposed. Subsequently, based on the measurements made on the insulators in operation, a new modeling method was verified. In conclusion, it can be stated that the 2XY model significantly improves the reliability of the dielectric response analysis, which should be confirmed in the future by tests on withdrawn and revised insulators.

Room temperature multiferroic properties of BiFeO3–MnFe2O4 nanocomposites

The novel functionalities of multiferroic magneto-electric nanocomposites have spawned substantial scope for fast-paced memory devices and sensor applications. Following this, herein we report the development of nanocomposites with soft ferromagnetic MnFe2O4 and ferroelectric BiFeO3 to fabricate a system with engineered multiferroic properties. A modified sol-gel route called Pechini method is demonstrated for the preparation of the (1-x) BiFeO3-x MnFe2O4 (x = 10%, 30%, 50%, 70%) nanocomposites. The crystallographic phase, structure, and morphology are characterized by XRD, FESEM, and HRTEM. The accurate crystallite size and lattice strain are determined by Williamson-Hall plot method and a comparative study with Scherer's equation is carried out. TEM image evidences the interface between BiFeO3 and MnFe2O4 nanoparticles in the composite. The room temperature magnetic response reveals the strong dependence of magnetic saturation, remanent magnetization, and coercivity of the nanocomposites on MnFe2O4 addition. The dielectric response and impedance analysis of the prepared nanocomposites are observed. The electrical performance of the composite is affected by grain, grain boundaries, and oxygen vacancies. The unsaturated P-E loops exhibit the leaky ferroelectric behavior for the nanocomposite. The intrinsic magnetoelectric coupling between ferroelectric BiFeO3 and ferromagnetic MnFe2O4 has been determined by varying Hdc/Hac and its maximum coupling coefficient (α) is found to be 25.39 mV/cmOe for 70% BiFeO3 -30% MnFe2O4 nanocomposite. These distinctive and achievable characteristics of the nanocomposite would enable the designing of magnetic field sensors, spintronic devices, and multiferroic memory devices.

Charge Transport Dynamics and Space Charge Accumulation in XLPE Composites with 2D Platelet Fillers for HVDC Cable Insulation

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.

Colossal dielectric response in CdAlxCu3-xTi4O12 perovskite ceramics

We designed Al-doped CdCu3Ti4O12 ceramics with large dielectric permittivity via a solid-state synthesis process. The dielectric permittivity of CdAlxCu3-xTi4O12 was induced to bring down and the dielectric loss increased upon Al doping. Remarkably, the change of dielectric behaviors are strongly associated with decreased grain boundary resistance. Meanwhile, internal barrier layer capacitor dielectric mechanism was regarded as the origin of the colossal dielectric behaviors combined with the analysis of dielectric responses and complex impedance. This study not only revealed the large dielectric permittivity mechanism of CdAlxCu3-xTi4O12 ceramics but also provided candidate ideas to realize a large dielectric permittivity and a lower dielectric loss in CdCu3Ti4O12 and other related dielectric ceramics.

Ultralow dielectric loss in Y‐doped SrTiO3 colossal permittivity ceramics via designing defect chemistry

AbstractEffects of doping of Y and sintering atmosphere on the dielectric properties of Sr1‐1.5xYxTiO3 ceramics (SYT, x = 0‐0.014) were systematically investigated. The SYT14 (x = 0.014) ceramic sintered in N2 attains a colossal permittivity (CP, Ɛr = 28 084@ 1kHz, 27 685@ 2MHz) and an ultralow dielectric loss (tanδ = 0.007@ 1kHz, 0.003@ 2MHz) at room temperature. Because of using of the A‐site deficient, there are in SYT ceramics. Through the comprehensive analysis of dielectric responses, X‐ray photoelectron spectroscopy (XPS), electron paramagnetic resonance (EPR), and complex impedance data, it is proved that doping of Y promotes the formation of (Y3+ are located at Sr2+ site), (Y3+ are located at Ti4+ site), and Ti3+, and sintering in reducing atmosphere of N2 results in more (oxygen vacancy) and (strontium vacancy) generating in SYT ceramics. The defect dipoles, , , , , , and formed by introduced defects make charge carriers localized in SYT ceramics. The combined action of the massive defect dipoles is responsible for the ultralow tanδ and CP in SYT14 ceramics sintered in N2.

Analysis of dielectric response of epoxy-mica insulation with temperature normalization

To decrease equipment costs and facilitate the simple and convenient on-site frequency dielectric spectroscopy (FDS) testing of epoxy-mica insulation of stator coils, specimens from a stator coil, subjected to 623 hours of 48 kV AC electrical ageing, were tested at temperatures from 0 to 120°C and frequencies from 10−1 to 107 Hz. The master curves and shift factors of the real and imaginary susceptibility components were obtained by the temperature normalization method. According to the horizontal shift factor, the complex susceptibility of the insulation increased exponentially with temperature. Regarding the vertical shift factor, the characteristic peak of the imaginary component of the complex susceptibility, representing the interface polarization of the epoxy-mica insulation, increased exponentially with temperature, and its movement can be expressed by the Arrhenius equation. The master curves of the temperature from 20 to 100°C and the frequency from 1 to 103 Hz can be fitted to the six-degree Debye relaxation model and Havriliak-Negami function. Through the shift factors and master curves, FDS data from 20 to 100°C can be estimated without temperature control.

Method for identifying ageing in epoxy‐mica composite insulation used in rotational machines through modelling of dielectric relaxation

Dielectric response analysis, performed in time domain and frequency domain is one of the interesting methods used for condition assessment of high voltage equipment. In this article, the degradation of epoxy-mica composite insulation which is widely used in rotating machines has been investigated through frequency domain spectroscopy measurements. Artificial ageing of the carefully prepared stator bar insulation sample was performed through simultaneous application of high temperature and electric field in a designated environmental chamber for specific durations. To study the effect of temperature, the measurements were performed at temperatures ranging from 20 to 60°C at different ageing status. Following experimental work, the measurement results were modelled using Havriliak–Negami model and ageing sensitive parameters were extracted. To study the effect of temperature, the measurements were performed at temperatures ranging from 20 to 60°C. The modelled results matched well with the experimental measurements and certain model parameters sensitive to the ageing condition were identified. The numerical relationships between the insulation status of the stator bar and the aforementioned parameters were identified. It was observed that the nature of the numerical relationship remains identical in the investigated temperature range, although the coefficients vary to some extent.

The effect of Sr doping on structural and dielectric properties of Ba2Co2Fe12O22 ceramics

Polycrystalline Ba2−xSrxCo2Fe12O22 (0 ≤ x≤0.5) ceramics have been synthesized by the conventional solid-state-reaction method. From the analysis of X-ray diffraction and scanning electron microscopy, it can be obtained that the lattice parameters decrease monotonically with the increase in Sr doping content, while the average grain size presents a complicated trend. The dielectric measurements show that dielectric constants of all samples are larger than 103 over a wide range of temperature and frequency (300–650 K and 1 kHz–1 MHz), which is identified as colossal dielectric constant. However, with the rise in Sr doping content, disparate evolutions of dielectric constant are found at 300 K and 600 K. A detailed study of dielectric response, impedance spectra and conductivity analysis suggest that the variation of dielectric constant at 300 K is dominated by the activation energy of relaxation, while that at 600 K is mainly in connection with the average grain size.

Dielectric constant and electrical study of solid-state electrolyte lithium phosphate glasses

A detailed analysis of dielectric response and electrical properties of lithium phosphate glasses (LiPO3) as a function of temperature from 20 °C (room temperature) to 170 °C and frequency from 4 Hz to 4 MHz was done using impedance spectroscopy technique. X-ray diffraction (XRD) and differential scanning calorimetry were used to study the structure phase and thermal analysis of the material under investigation, respectively. XRD pattern confirms the amorphous nature of the material. The total conductivity shows two distinct regions, dc conductivity and ac conductivity (σtot(ω) = σdc + A ωr). The ac conductivity’s exponent factor r was found invariant at low-temperature zone and temperature dependent at high-temperature zone. The frequency exponent factor values and its temperature dependence suggested that the jump relaxation model is the best model that can describe the conduction mechanism. Various parameters such as bulk conductivity, dc conductivity, dielectric relaxation time, transition time and the associated activation energies were calculated and discussed. The activation energy of bulk conductivity, dc conductivity and the dielectric relaxation was found to have similar value (0.29 eV). Thermodynamic parameters, such as free energy of activation (ΔF), enthalpy of activation (ΔH) and entropy of activation (ΔS), have been calculated and discussed as well.