Dielectric Response Research Articles

Phase Diagram and Dielectric Response of Hybrid Lead Halide Hollow Perovskites: A Universal Behavior of Molecular Cation Mixing

Phase Diagram and Dielectric Response of Hybrid Lead Halide Hollow Perovskites: A Universal Behavior of Molecular Cation Mixing

Study on the giant dielectric response of Ca1-xSrxCu3Ti4O12/TiO2 composite ceramics with a hierarchical grain boundary structure

In this study, Ca1-xSrxCu3Ti4O12/TiO2 ceramics doped with different Sr/Ca ratios and an excess of 20% nano-scale TiO2 particles were prepared via the solid-state method (denoted as C1-xSxCTO/TiO2, where x = 0, 0.2, 0.4, 0.6, 0.8, 1.0). The phase composition, microstructure, elemental distribution, elemental valence states, and electrical properties of the composite ceramics were systematically analyzed. XRD data confirmed the successful synthesis of CSCTO crystals in a series of CSCTO ceramics, and it was observed that the lattice parameters of the main phase increased as the Sr/Ca ratio in CSCTO/TiO2 increased. Ca0.8Sr0.2Cu3Ti4O12/TiO2 ceramics demonstrated a good dielectric constants (1 × 105, 1 kHz) at room temperature. Microstructure analysis revealed that the excess TiO2 hinders the composite ceramics' crystal growth, forming pomegranate-like structures. The structure leads to a hierarchical interfacial polarization, which results in the giant dielectric response in CSCTO/TiO2 composite ceramics.

Peculiarities of Electric and Dielectric Behavior of Ni- or Fe-Doped ZnO Thin Films Deposited by Atomic Layer Deposition.

The physical properties of ZnO can be tuned efficiently and controllably by doping with the proper element. Doping of ZnO thin films with 3D transition metals that have unpaired electron spins (e.g., Fe, Co, Ni, etc.) is of particular interest as it may enable magnetic phenomena in the layers. Atomic layer deposition (ALD) is the most advanced technique, which ensures high accuracy throughout the deposition process, producing uniform films with controllable composition and thickness, forming smooth and sharp interfaces. In this work, ALD was used to prepare Ni- or Fe-doped ZnO thin films. The dielectric and electrical properties of the films were studied by measuring the standard current-voltage (I-V), capacitance-voltage (C-V), and capacitance-frequency (C-f) characteristics at different temperatures. Spectral ellipsometry was used to assess the optical bandgap of the layers. We established that the dopant strongly affects the electric and dielectric behavior of the layers. The results provide evidence that different polarization mechanisms dominate the dielectric response of Ni- and Fe-doped films.

Hygrothermal Degradation of Epoxy Electrical Insulating Material-Testing and Mathematical Modeling.

The degradation of electrical insulating materials has been a subject of interest for decades as they are commonly applied in many fields of electrical engineering. Suitably modeling such a process is important since the known and well-described degradation process reveals the effect of ambient conditions, and this allows us to possibly estimate a material's remaining useful life. However, not many studies are dealing with the effect of the hygrothermal degradation of impregnating mono-component epoxy resins in the context of electrical engineering. Therefore, this study deals with this issue and discusses both the dielectric response (based on the measurement of relative permittivity, dissipation factor, and dielectric strength) and the mechanical response (based on measurements of tensile strength and Shore D hardness) to a hygrothermal degradation experiment. In addition, the results of thermal analyses are presented for the evaluation of the pristine specimen manufacturing process and possible post-curing processes. Furthermore, this study presents several methodologies for modeling the degradation process, including a novel methodology in this area based on Bayesian experimental design. As an outcome, mechanical parameters are proven to be specific in terms of the actual condition of the material and the Bayesian enhanced degradation model seems to be superior to the conventional evaluation methods in this particular study.

A novel mathematical approach for modeling the dielectric response surface of the transformer oil to predict the optimized functions of transformers in high-power applications

A novel mathematical approach for modeling the dielectric response surface of the transformer oil to predict the optimized functions of transformers in high-power applications

Voltage-induced modulation of interfacial ionic liquids measured using surface plasmon resonant grating nanostructures.

We have used surface plasmon resonant metal gratings to induce and probe the dielectric response (i.e., electro-optic modulation) of ionic liquids (ILs) at electrode interfaces. Here, the cross-plane electric field at the electrode surface modulates the refractive index of the IL due to the Pockels effect. This is observed as a shift in the resonant angle of the grating (i.e., Δϕ), which can be related to the change in the local index of refraction of the electrolyte (i.e., Δnlocal). The reflection modulation of the IL is compared against a polar (D2O) and a non-polar solvent (benzene) to confirm the electro-optic origin of resonance shift. The electrostatic accumulation of ions from the IL induces local index changes to the gratings over the extent of electrical double layer (EDL) thickness. Finite difference time domain simulations are used to relate the observed shifts in the plasmon resonance and change in reflection to the change in the local index of refraction of the electrolyte and the thickness of the EDL. Simultaneously using the wavelength and intensity shift of the resonance enables us to determine both the effective thickness and Δn of the double layer. We believe that this technique can be used more broadly, allowing the dynamics associated with the potential-induced ordering and rearrangement of ionic species in electrode-solution interfaces.

Electric and dielectric responses of Au/n-Si structure by Mn doped PVC interfacial layers

This paper has investigated and compared the impact of polyvinyl chloride (PVC) without/with manganese (Mn) metallic nanoparticles interfacial layer on the electric and impedance characteristics of Schottky diode (SD) with a structure of Au/n-Si (MS). The structures of these two metal-polymer-semiconductor (MPS) SDs are Au/PVC/n-Si and Au/PVC:Mn/n-Si. A detailed description of the SDs manufacturing process is given. The x-ray diffraction (XRD) analysis, Scanning Electron Microscope (FE-SEM) images, and Electron Dispersive x-ray (EDX) spectroscopy are three methods that have been utilized to examine mean size of crystallite, morphology of surface, purity specification. The fundamental electronic variables of these devices are ascertained and contrasted with one another using the I-V characteristic measurement at ±6 V. Ohm’s law, Thermionic Emission (TE) theory, modified Norde, and Cheung functions are used to calculate the SDs’ leakage current (I0), ideality coefficient (n), potential barrier height (BH), shunt (Rsh), and series (Rs) resistances. Investigations are conducted on the energy dependence of surface states density (Nss) and the current conduction mechanisms (CCMs) for both reverse and forward biases. These interfacial layers are known to decrease the n, Rs, and Nss. The PVC polymer interlayer leads to improve the efficiency of the MS-type SD, but it does not when doped by Mn nanoparticles. Additionally, by measuring impedance at a bias of 1.5 V and 100 Hz-1 MHz frequency range, the frequency dependence of dielectric properties of the prepared SDs is studied. The dielectric permittivity, dielectric loss tangent, electronic modulus, and ac electronic conductivity of these SDs are all studied.

Improved Dielectric Response of Solids: Combining the Bethe-Salpeter Equation with the Random Phase Approximation.

The Bethe-Salpeter equation (BSE) can provide an accurate description of low-energy optical spectra of insulating crystals-even when excitonic effects are important. However, due to high computational costs it is only possible to include a few bands in the BSE Hamiltonian. As a consequence, the dielectric screening given by the real part of the dielectric function can be significantly underestimated by the BSE. Here, we show that universally accurate optical response functions can be obtained by combining a four-point BSE-like equation for the irreducible polarizability with a two-point Dyson equation that includes the higher-lying transitions within the random phase approximation. The new method is referred to as BSE+. It has a computational cost comparable to the BSE but a much faster convergence with respect to the size of the electron-hole basis. We use the method to calculate refractive indices and electron energy loss spectra for a test set of semiconductors and insulators. In all cases the BSE+ yields excellent agreement with experimental data across a wide frequency range and outperforms both the BSE and the random phase approximation.

Time-domain constraints for passive materials: The Brendel-Bormann model revisited

This paper presents a systematic approach to derive physical bounds for passive systems, or equivalently for positive real (PR) functions, directly in the time-domain (TD). As a generic, canonical example we explore the TD dielectric response of a passive material. We will furthermore revisit the theoretical foundation regarding the Brendel-Bormann (BB) oscillator model which is reportedly very suitable for the modeling of thin metallic films in high-speed optoelectronic devices. To this end, an important result here is to re-establish the physical realizability of the BB model by showing that it represents a passive and causal system. The theory is based on Cauer's representation of an arbitrary PR function together with associated sum rules (moments of the measure) and exploits the unilateral Laplace transform to derive rigorous bounds on the TD response of a passive system. Similar bounds have recently been reported for more general casual systems with other assumptions. To this end, it is important to note here that the existence of useful sum rules and related physical bounds rely heavily on an assumption about the PR functions having a low- or high-frequency asymptotic expansion at least of odd order 1. As a particular numerical example, we consider here the electric susceptibility of gold (Au) which is commonly modeled by well established Drude or BB models. Explicit physical bounds are given as well as an efficient fast-Fourier transform -based numerical procedure to compute the TD impulse response associated with the nonrational BB model. Published by the American Physical Society 2024

DLC: Flexible bridge across heterogeneous interface between alumina filler and epoxy resin matrix

The heterogeneous interface between filler and matrix within composites often acts as a bottleneck for material performance. Carbon materials, particularly Diamond-Like Carbon (DLC), are representing a novel trend in interface design. This study investigates the nanoscale mechanical and electrical properties of the heterogeneous interface between DLC-coated alumina fillers and an epoxy resin matrix. The results demonstrate that the DLC layer is instrumental in creating a harmonious modulus transition between materials that exhibit significant variance in their elastic moduli, characterized by an exponential relationship, and approximately 50% enhancement in interfacial adhesion. Additionally, the DLC layer exhibits elevated sensitivity in dielectric response, attributed to a small RC time constant. This interface transition technology offers new tools for composite material design.

Analysis of a film-forming amine response in impedance spectra

In this study, a detailed analysis of the dielectric response of a film-forming amine (1,3 N-oleyl propanediamine (OLDA)) in impedance spectra is presented, addressing both “bulk” OLDA and adsorbed OLDA layer on a carbon steel surface. The dielectric response of the “bulk” OLDA in the absence of electrolyte over an extensive temperature range (-150 °C to 50 °C) was explored by broadband dielectric spectroscopy (BDS). Subsequently, the response of the OLDA adsorbed layer on the steel surface was analysed by electrochemical impedance spectroscopy (EIS), for various immersion times (2 min to100 min) and temperatures (25 °C to 75 °C) in an aqueous NaCl solution.Impedance spectra (BDS and EIS), interpreted through the complex conductivity formalism, showed a resistive behaviour in the mid-frequency range and a capacitive behaviour at higher frequencies. The high frequency capacitive response in EIS spectra was shown to contain contributions from the OLDA layer and from the electrochemical double layer, as well. The temperature dependency of the OLDA conductivity was found to be similar to the temperature dependency of the electrolyte resistance, suggesting that the electrolyte (water and ions) crossed the OLDA layer to reach the steel surface. The presence of gauche defects in the OLDA alkyl chain, revealed by polarization modulation infrared reflection absorption spectroscopy (PM-IRRAS) analyses, may be a contributing factor to the disorder in the adsorbed layer, facilitating electrolyte infiltration.

Microstructure, optical, dielectric, and nonlinear properties of Cd1-xBi2x/3Cu3Ti4O12 ceramics

Microstructure features along with optical, dielectric and nonlinear properties of Cd1-xBi2x/3Cu3Ti4O12 (x = 0, 0.3, 0.6, 0.9, and 1.0) ceramics were investigated systematically. With increase in Bi3+ doping content, Cd1-xBi2x/3Cu3Ti4O12 structure sightly distorted and eventually formed more stable configuration. Bi3+ doping also caused grain refinement and increased compactness of ceramics, whereas Bi-rich phase appeared at grain boundaries. Optical band gap (Eg) decreased due to increase in defect concentration. Dielectric loss (tanδ) dropped with increase in Bi3+ doping content while dielectric constant (ɛ′) remained high. The most optimal dielectric characteristics (the lowest tanδ of ∼0.033, giant ɛ′ of ∼10028 at 10 kHz and room temperature, the highest nonlinear coefficient (α of 4.62) and breakdown field strength (Eb of up to ∼9.23 kV/cm) were achieved at x = 0.9. Impedance spectra revealed semiconducting grains and insulating grain boundaries. Dielectric response evolution in Cd1-xBi2x/3Cu3Ti4O12 ceramics was described using internal barrier layer capacitor model. Electric modulus values indicated that low-frequency relaxation originated from grain boundaries. High energy barrier of grain boundaries was beneficial for enhancement of nonlinear properties of ceramics. Thus, Bi3+ doping improved both dielectric and nonlinear characteristics of Cd1-xBi2x/3Cu3Ti4O12 ceramics.

Tailoring Bi1−x−yBaxFeyFeO3 for desired properties: insights into structural, dielectric, and magnetic responses

In present study, samples of Bi1−x−yBaxFeyFeO3 have been synthesized, where x = 0.15, y = 0; x = 0.10, y = 0.10; and x = 0.15, y = 0.10 utilizing a swift two-stage solid-state reaction method. X-ray diffraction (XRD) data has been Rietveld refined to evaluate the structural parameters. Micro-strain is also calculated using Williamson Hall method. Temperature (300 K to 660 K) dependent measurements of the dielectric constant have been conducted at various frequencies (100 kHz, 500 kHz, and 1000 kHz). The dielectric constant (ε′) rises as the temperature increases. Two dielectric anomalies around 450 K and 613 K have been noticed in ε′ versus T curves for all the samples which might be related with defect dipoles and the magnetic transition respectively. Further, an insignificant value of loss tangent (0.2) specifically at around 300 K is a signal of small leakage current in the samples. The source of high dielectric constant is discussed by considering the structural distortions in the ceramics. A clear hysteresis loop has been observed for all the samples which is a sign of collapse of antiferromagnetic nature of BiFeO3. Further, in case of co-doped samples, almost a saturation in magnetization with magnetization value 5.9718 emu g−1 has been noticed in hysteresis curve indicating a major contribution of ferromagnetic interaction. Enhancement in the net magnetization is briefly discussed by considering the ferromagnetic type direct interaction among Fe3+ ions and suppressing the anti-ferromagnetic type super exchange interaction.

Nonlocal structural effects of water on DNA homology recognition

The mechanism behind mutual recognition of homologous DNA sequences prior to genetic recombination is one of the remaining puzzles in molecular biology. Leading models of homology recognition, based on classical electrostatics, neglect the short-range nonlocal screening effects arising from structured water around DNA, and hence may only provide insight for relatively large separations between interacting DNAs. We elucidate the role of the effects of the nonlocal dielectric response of water on DNA–DNA interaction and show that these can dramatically enhance the driving force for recognition.

Doublet doped titanate ferroelectric system for capacitors and NTC thermistor applications

A simple negative temperature coefficient (NTC) thermistor Ba0.85Sr0.15Ti0.85Zr0.15O3 system is elaborated using a conventional solid-state reaction route. The structural analysis confirms that the elaborated pseudo-cubic system, which is indexed in the P4mm space group, exhibits one single phase. The dielectric properties and the electrical resistivity data are investigated over a large temperature range from 413 K to 673 K. In this temperature interval, the Steinhart–Hart equations are employed to confirm that Ba0.85Sr0.15Ti0.85Zr0.15O3 is a promising system for sensor application. Accordingly, the thermistor constant (β=10154 K), the sensitivity factor (-5.5 %/K≤α≤-2 %/K), the activation energy (Ea=0.875 eV), and the stability factor (SF=2.27) parameters are calculated to approve that Ba0.85Sr0.15Ti0.85Zr0.15O3 exhibits an NTC-thermistor behavior. The temperature dependence of the electrical resistivity confirms that Ba0.85Sr0.15Ti0.85Zr0.15O3 reveals a semiconductor behavior. The dielectric investigation shows that Ba0.85Sr0.15Ti0.85Zr0.15O3 exhibits a motivating dielectric properties (elevated dielectric constant value (105<ε’<106) and low dielectric losses (mostly < 0.007) with almost frequency independence between 20 Hz to 500 kHz). The colossal dielectric response of Ba0.85Sr0.15Ti0.85Zr0.15O3 is attributed to the internal barrier layer capacitor (IBLC) and the surface barrier layer capacitor (SBLC) effects. Such response suggests the suitability of Ba0.85Sr0.15Ti0.85Zr0.15O3 ceramic for high temperature capacitor applications.

Multi-physical channels response in a novel layered perovskite: (trans-4-methylcyclohexylammonium)2[CuCl4]

With the continuous development of society, the demand for multi-physical channel responsive materials continues to increase, and it is urgent to develop multi-channel responsive materials with excellent properties. Here, in this work, we reported a novel two-dimensional (2D) organic–inorganic hybrid perovskite, (trans-4-methylcyclohexylammonium)2[CuCl4] (1), with responsive multi-physical channels. 1 experienced a structural phase transition with switchable thermochromism and dielectric response, which has great potential in the application of responsive materials. Under thermal stimulation, crystal 1 displays a reversible color variation between green and yellow. Crystal structure determination reveals that the distortion of inorganic layers plays a predominant role in the thermochromism during the phase transition process. This finding presents a compelling avenue for developing multi-physical channel responsive materials and contributes valuable insights to the exploration of two-dimensional lead-free perovskites for applications in intelligent window technology.

Effect of vermicompost additive on physical, chemical and dielectric properties of soil and its modeling

The present study focuses on the effects of vermicomposting on various soil properties, particularly emphasizing the dielectric characteristics of soil. Vermicomposting is known to significantly enhance soil fertility and improve its physical aspects such as aeration, porosity and water retention. In this analysis, a modified probe arrangement has been employed to determine how varying levels of vermicompost influence the soil’s dielectric properties within the radio and microwave spectrum (10 MHz-14 GHz). A modified Dak-12 open-ended coaxial probe, paired with a vector network analyzer, was utilized for this purpose to overcome the drawbacks of standard arrangement. The results show that vermicompost strongly affects the soil’s physical attributes (pH, bulk density, porosity) and also its chemical properties, along with its dielectric behavior. The study further explored the role of different factors such as the concentration of vermicompost, frequency and temperature on soil’s dielectric response. To accurately and swiftly gauge these effects, Response Surface Methodology (RSM) has been employed to predict the dielectric properties (ε’ and ε’’) of the soil. The high precision of these models, with R 2 values of 0.9729 for ε’ and 0.9487 for ε’’, underscores their effectiveness in evaluating the impact of vermicompost on various soil properties.

Effects of finite counterion size and nonhomogeneous permittivity and viscosity of the solution on the electrokinetics of a concentrated salt-free colloid.

In the present work, a general model of the electrokinetics and dielectric response of a concentrated salt-free colloid is developed which includes consideration of the finite size of the counterions released by the particles to the solution, a nonhomogeneous permittivity of the solution, the existence of Born and dielectrophoretic forces acting on the counterions, and especially the fact that the solution viscosity and diffusion counterion coefficient are allowed to be functions of the local counterion concentration. These effects have recently been discussed by J. J. López-García etal. [Phys. Rev. Fluids 4, 103702 (2019)10.1103/PhysRevFluids.4.103702] in the case of dilute colloids in general electrolyte solutions. The objective of this work is to explore the new effects and their influence on the electrokinetic response of concentrated salt-free systems. Present results confirm previous findings regarding the important increases of the dc electrophoretic mobility and dc electrical conductivity, as well as huge increments of the dynamic electrophoretic mobilities at high frequencies when finite-ion-size effects were taken into account. In addition, consideration of the viscosity of the solution and of the counterion diffusion coefficient as functions of the local counterion concentration leads to a decrease of the magnitude of the previous electrokinetic results. The theory incorporates a more convenient hard-sphere hydrodynamic model to account for the nonhomogeneous viscosity of the solution than others proposed in previous works in the literature. A comparison is elaborated on between electrokinetic and dielectric responses with different levels of complexity of the theoretical model, starting from the case of pointlike counterions and following with the inclusion in sequence of additional aspects such as finite counterion size, nonhomogeneous electrical permittivity with associated Born and dielectrophoretic effects, and, finally, position-dependent viscosity and diffusion counterion coefficient, and clearly shows the influence of individual effects on the general electrokinetic response and especially the relevant role the nonhomogeneous viscosity on the dc and ac electrokientic behavior of salt-free colloids.

Ultra-small size and crystal-axis-oriented BaTiO3 nanocrystals: Dielectric and photocatalytic response

With the development of modern nanotechnology, the application range of BaTiO3 (BT) materials has been expanded, and the design and synthesis of micro-nano scale BT materials have become one of the hot spots. In this study, ultra-small BaTiO3 (Ultra-BT) were prepared by solvothermal-calcination reaction. First, the BT precursor was prepared by solvothermal reaction with ethylene glycol as solvent, and then the BT precursor was calcined to obtain Ultra-BT. The Ultra-BT at this time is composed of uniform [010]-crystal-axis-oriented BT nanocrystals with a size of about 28 nm. The formation mechanism of Ultra-BT was revealed, namely the dissolution-deposition reaction. Ultra-BT are more favorable for the preparation of BT ceramics with uniform grain because of their ultra-small size. At a sintering temperature of 1220 °C, the dielectric constant of BT ceramics at the Curie temperature is 8661. This dielectric constant value is higher than that reported for BT ceramics in most literature, and even higher than some doped modified BT ceramics. The solvothermal-calcination method used for preparing Ultra-BT provides important reference value for the preparation of other ultra-small perovskite materials. At the same time, because of the excellent dielectric properties and good catalytic properties of Ultra-BT, it has potential application value in the field of dielectric and catalysis.

Research on equivalent modeling of wideband dielectric response of oil-paper insulation based on the Kramers-Kronig transform

Research on equivalent modeling of wideband dielectric response of oil-paper insulation based on the Kramers-Kronig transform