Dispersion Of Dielectric Permittivity Research Articles

Radiation in a plasma and applications to cosmic microwave background

AbstractIn a recent paper [Phys. Rev. E 100, 023202 (2019)], Munirov and Fish proposed application of the well‐known approach for the calculation of the fluctuation field radiation spectrum in a transparent fully ionized plasma to the problem of cosmic microwave background. They used the result for spectral energy distribution of the equilibrium radiation, assuming that the spectrum of free photons is changed to the non‐damping spectrum of transverse waves in non‐relativistic plasma. The similar approach has been considered earlier by several authors for non‐relativistic and relativistic plasmas. The results of Munirov and Fish are in fact in perfect agreement with the most of the previously existing expressions. However, we argue that this approach based on such simple approximation is not enough justified and the more elaborated consideration, taking into account not only temporal but also spatial dispersion of dielectric permittivity is necessary for a consistent description of radiation in plasmas. Moreover, interaction between free photons and charged particles in the framework of quantum electrodynamics leads to the result different in comparison with the standard consideration even for the transparent plasma medium.

Dielectric Relaxation in a Nanosize Ferroelectric with an Incommensurate Phase Rb2ZnCl4

The dielectric properties of a composite obtained by embedding a ferroelectric salt Rb2ZnCl4 into a porous glass matrix with an average size of through pores of about 46 nm have been studied within the temperature range of 100–350 K at frequencies of 5–500 kHz. An increase in the dielectric permittivity dispersion depth Δε upon sample cooling, due to an increase in the concentration of “relaxers” and an increase in their dipole moment, was found. An analysis of the dielectric response features showed that a domain structure is formed in the ferroelectric phase of Rb2ZnCl4 particles, the mobility of which in the vicinity of the freezing temperature Tf obeys the empirical Vogel–Fulcher relation

Temperature-driven structural phase transitions in 0.05(Na0.50Bi0.50)TiO3-0.95NaNbO3 solid solution via amplitude mode analysis

Structural phase transitions in the ABO3-type lead-free eco-friendly piezoelectric (05NBT) have been studied as a function of temperature using dielectric and X-ray diffraction techniques. Below 300 K, we observed dispersion in dielectric permittivity with the frequency, which confirmed relaxor behaviour in 05NBT. Using detailed analysis of temperature-dependent powder X-ray diffraction data of 05NBT, four phase transitions were identified across 600 K, 773 K, 823 K and 923 K. We found that on doping 5% NBT in pure sodium niobate, the low-temperature rhombohedral ferroelectric (N) phase and the high-temperature (S) phase of the sodium niobate get suppressed. To get a better insight about the temperature-driven structural phase transitions, various antiferrodistortive and additional distortive mode as well as the mode amplitude relative to high-symmetry cubic phase were computed and results are discussed.

Composition controllable multifunctionality of PVDF/PMMA/BaTiO3/OMMT based ternary and quaternary hybrid polymer nanocomposites

State-of-the-art engineered multifunctional nanocomposites composed of different polymer matrices and functional nanomaterials are in high industrial demand for advances in all-solid-state flexible device technologies. Within this framework, the host matrices of poly(vinylidene fluoride) (PVDF) and its blend with poly(methyl methacrylate) (PMMA), and the barium titanate (BaTiO3) and organo-modified montmorillonite (OMMT) clay mixed nanomaterial dispersed ternary PVDF/x wt% (BaTiO3+OMMT) and quaternary (PVDF+PMMA)/x wt% (BaTiO3+OMMT) hybrid polymer nanocomposites (HPNCs) are prepared through ultrasonicated homogenized solution casting method. The XRD patterns and FTIR transmittance spectra confirmed the composition dependent crystal phases of the PVDF and the heterogeneous polymer-polymer and polymer-nanomaterial interactions in these HPNC materials. The DSC measurements explained a huge alteration in the PVDF crystallite melting temperatures and also the degree of crystallinity of different HPNC materials. The UV–Vis absorbance of these hybrid materials depends strongly on their composition design and demonstrated dual energy band gaps attributed to host polymer matrices and the nanofillers. The dielectric permittivity dispersion in the broadband frequency range of 20 Hz − 1 GHz explains the contribution of several polarizations and relaxation processes in these complex composites, at 27 °C. Appreciably high dielectric permittivity (4 to 7) in the 20 Hz − 1 MHz range and low permittivity at the ultra high radio frequencies confirmed the promising nanodielectric characteristics of these hybrid materials. The interesting structure-property relationship, tunable energy band gaps, a wide range of composition controllable dielectric permittivity, and frequency dependent electrical conductivity revealed the usefulness of these HPNCs in making flexible-type innovative optoelectronic, capacitive energy storage, and microelectronic devices.

Frequency Response of a Ferroelectric Composite Synthesized from Cellulose Nanoparticles and Rochelle Salt

The study provides frequency spectra of several electrophysical parameters of dielectric permittivity, dielectric loss tangent, conductivity, electrical impedance and electric modulus to explore the frequency response at low and infralow frequencies (10−2–106 Hz) for the ferroelectric composite synthesized from cellulose nanoparticles and Rochelle salt. The experimental results confirmed the main contribution of conductivity into the frequency response with the presence of two relaxation processes. The first one was related to the intrinsic relaxation inside the composite while the second one was caused by the influence of electrode effects. Besides, the significant dispersion of dielectric permittivity obeying Maxwell-Wagner-Sillars mechanism has also been detected.

Multifrequency Inversion of Complex Electrical Conductivity Measurements for Simultaneous Assessment of Wettability, Porosity, and Water Saturation

Summary Multifrequency complex electric measurements are influenced by the joint effects of mineralogy, spatial distribution of fluids and solids, properties of fluids and minerals, and interfacial polarization mechanisms. The interpretation of multifrequency electrical conductivity and dielectric permittivity dispersion can yield information about the dominant dielectric polarization mechanisms. The dielectric polarization mechanisms detected in sedimentary rocks are linked to grain size, shape, and orientation relative to the externally applied electric field, electrochemical adsorption/desorption complexation reactions, wettability, porosity, and fluid saturations. In this work, we introduce a new workflow for multifrequency interpretation of complex permittivity measurements. The introduced workflow enables simultaneous assessment of dominant wettability, porosity, and hydrocarbon reserves. These properties are estimated by minimizing a cost function using a combination of downhill gradient-descent and an evolutionary algorithm. The cost function quantifies the difference between measured and numerically calculated multifrequency complex dielectric permittivity through a recently introduced rock-physics model. We successfully applied the new interpretation workflow to multifrequency electrical resistivity/permittivity measurements obtained from two water-wet and two hydrocarbon-wet sandstone core samples. Simultaneous estimates of wettability, water saturation, and porosity obtained by applying the new interpretation workflow were in agreement with experimental measurements. Assessment of hydrocarbon reserves, porosity, and dominant wettability solely from the interpretation of multifrequency complex-valued electrical measurements is a unique contribution of the introduced workflow. Additionally, the new workflow honors rock fabric and, thus, it minimizes the necessity of extensive calibration efforts. All the parameters needed as inputs to the new interpretation workflow are associated with physical mechanisms at microscopic- and pore-scale domains or realistic and quantitative pore geometry features of the rock.

Numerical modeling of multifrequency complex dielectric permittivity dispersion of clay-rich rocks

Dielectric permittivity measurements in sedimentary rocks are dominated by mineralogy, the volumetric concentration and spatial distribution of solids and fluids, and interfacial polarization. Conventional interpretation models oversimplify these factors, leading to uncertainties in estimates of formation properties such as hydrocarbon reserves. Interpretation challenges are magnified in clay-rich rocks, such as shaly sands and organic-rich mudrocks, due to convoluted rock fabric and mineralogical composition. However, the impact of fabric features and mineralogy on broadband permittivity is not well understood. Therefore, the main objective of this work is to develop a numerical framework to quantify the impact of different minerals and corresponding spatial distribution on the multifrequency complex permittivity of clay-rich rocks. We have solved the quasielectrostatic approximation to Maxwell’s equations in the frequency domain through the finite-volume method. We also introduce a workflow to calculate the effective admittance of the clay network. Furthermore, we derive an equation to incorporate the induced polarization effect into the effective admittance of pyrite particles. Finally, we perform a sensitivity analysis of the complex permittivity of clay-rich rocks in the frequency range from 100 Hz to 1 GHz to the volumetric concentration and spatial distribution of clays, cation exchange capacity (CEC), volumetric concentration of pyrite, and the orientation of the electric field. The simulation results confirm that the presence of clay minerals affects the permittivity and conductivity of the rocks. However, clays can enhance or diminish electrical conductivity values at different frequencies depending on their intrinsic properties and spatial distribution. For instance, laminations significantly enhance permittivity in the sub-MHz frequency range, but their effect is imperceptible at 1 GHz. The CEC variation affects conductivity in the entire frequency range from 100 Hz to 1 GHz and the permittivity at sub-MHz frequencies. A volumetric concentration of pyrite of 5% can enhance permittivity and conductivity at 100 Hz by approximately 50% and 30%, respectively.

Numerical modeling of multifrequency complex dielectric permittivity dispersion of sedimentary rocks

The dielectric response of rocks results from electric double layer (EDL), Maxwell-Wagner (MW), and dipolar polarizations. The EDL polarization is a function of solid-fluid interfaces, pore water, and pore geometry. MW and dipolar polarizations are functions of charge accumulation at the interface between materials with contrasting impedances and the volumetric concentration of its constituents, respectively. However, conventional interpretation of dielectric measurements only accounts for volumetric concentrations of rock components and their permittivities, not interfacial properties such as wettability. Numerical simulations of the dielectric response of rocks provide an ideal framework to quantify the impact of wettability and water saturation ([Formula: see text]) on electric polarization mechanisms. Therefore, we have developed a numerical simulation method to compute pore-scale dielectric dispersion effects in the interval from 100 Hz to 1 GHz including effects of pore structure, [Formula: see text], and wettability on permittivity measurements. We solve the quasielectrostatic Maxwell’s equations in 3D pore-scale rock images in the frequency domain using the finite-volume method. Then, we verify simulation results for a spherical material by comparing to the corresponding analytical solution. Additionally, we introduce a technique to incorporate [Formula: see text]-polarization to the simulation and we verify it by comparing pore-scale simulation results to experimental measurements on a Berea sandstone sample. Finally, we quantify the impact of [Formula: see text] and wettability on broadband dielectric permittivity measurements through pore-scale numerical simulations. The numerical simulation results show that mixed-wet rocks are more sensitive than water-wet rocks to changes in [Formula: see text] at sub-MHz frequencies. Furthermore, permittivity and conductivity of mixed-wet rocks have weaker and stronger dispersive behaviors, respectively, when compared to water-wet rocks. Finally, numerical simulations indicate that conductivity of mixed-wet rocks can vary by three orders of magnitude from 100 Hz to 1 GHz. Therefore, Archie’s equation calibrated at the wrong frequency could lead to water saturation errors of up to 73%.

Dielectric relaxation and variable range hopping conduction in sol-gel auto combustion derived La0.7Bi0.3Fe0.5Mn0.5O3 manganite

In the present work, the polycrystalline La0.7Bi0.3Fe0.5Mn0.5O3 maganite was synthesized by sol-gel auto-combustion method. The room temperature X-ray powder diffraction pattern confirmed the orthorhombic phase of the sample with pbnm space group. Frequency and temperature dependent electric modulus and impedance spectroscopic analyses revealed two electro-active components of the material characterized by highly resistive grain boundaries and comparatively conducting grains, respectively. The normalized scaling behavior of modulus plots divulged the temperature independence of the dynamic process in electro-active regions. The fitting of impedance data by the equivalent circuit (RG||QG) + (RGB||QGB) was applied to explore the physical parameters associated with grains and grain boundaries. The dispersion in dielectric permittivity and loss factor at lower frequencies attributed to the space charge polarization were observed. The electrical conductivity obeyed Mott’s T1/4 law and the slope of frequency dependent AC conductivity spectra changed due to multiple activation barriers and active traps, consistent with the variable-range hopping conduction in the material.

The effect of an AC electric field on the dielectric properties of Pb(Mg1/3Nb2/3)O3 ceramic

The dynamic dielectric response of Pb(Mg1/3Nb2/3 )O3 ceramic was experimentally studied as a function of the EAC amplitude field. An increase in real dielectric permittivity was obtained by increasing the applied electrical field within the investigated temperature range for frequencies below 10 kHz. The temperature of maximum dielectric permittivity and freezing temperature decreased with an increase in E AC. Nonlinear permittivity was studied and found to behave similarly to freezing temperature. A statistical model was used to fit the dielectric dispersion of real dielectric permittivity with temperature and frequency. The results are discussed in terms of different factors’ contributions to dielectric permittivity under different EAC field conditions.

Multifrequency Analytical Forward Modeling of Dielectric Permittivity Dispersion in Mixed-Wet Sedimentary Rocks

Summary The dominant wettability of reservoir rocks is one of the main factors affecting the spatial distribution of fluids inside the pore space. More specifically, wettability controls the fluid type that coats the surface of the grains and, hence, the establishment of an electric double layer (EDL) at the solid–liquid interface. These factors, namely fluid distribution and EDL, affect the conductivity and permittivity of the rock in unique ways. Therefore, interpretation of multifrequency complex permittivity measurements can be used to quantify the wettability and parameters affecting the double layer (e.g., grain size) in addition to porosity and fluid saturation. In this paper, we introduce an analytical model to reliably characterize the dielectric permittivity dispersion of mixed-wet sedimentary rocks. The analytical derivation of the rock-physics model results in physically meaningful parameters, associated with either microscopic polarization mechanisms or pore-network geometry. We incorporate the contribution of the complex impedance associated with the EDL to the complex permittivity of the rock through a mechanistic model of Stern and Gouy-Chapman layers. Then, we quantify the contribution of different fluid and grain types to the electrical response of sedimentary rocks through Hanai–Bruggeman effective medium model. The sequential application of Hanai-Bruggeman is specifically designed to make the dependence of complex permittivity on wettability explicit. We successfully verified the reliability of the new analytical model using experimental measurements performed on two water-wet and two hydrocarbon-wet sandstone core samples. The experimental measurements were in agreement with the complex permittivity calculated using the new analytical model in the frequency range of 100 Hz to 10 MHz. Furthermore, the introduced model provides a physical interpretation to the experimentally detectable influence of wettability on the complex dielectric permittivity of rocks. Consequently, the outcomes of this paper will enhance petrophysical evaluation in mixed-wet formations by providing a novel interpretation method for complex permittivity dispersion measurements.

Structural and dielectric characterization of (PVP/PEO)/Al2O3 nanocomposites for biodegradable nanodielectric applications

Polymer host matrix and inorganic nanofiller comprising hybrid nanocomposites of integrated promising properties are the most appealing multifunctional materials for developing advanced flexible-type electrical and electronic devices and also a variety of daily life quality products. This research reports the structural parameters and dielectric properties of biodegradable poly(vinyl pyrrolidone)/poly(ethylene oxide) (PVP/PEO) blend matrix and alumina (Al2O3) nanoparticle–based polymer nanocomposite (PNC) films. Porous spherulitic morphology of the host PVP/PEO matrix, polymer-polymer interactions, and the structures of PEO crystallites are found largely influenced by the Al2O3 nanofiller, whereas the degree of crystallinity of the PNC films increases slightly. The dielectric permittivity of the PNC films over 20 Hz to 1 MHz frequency range confirmed some increase in dielectric polarization, but they exhibited anomalous behavior when the Al2O3 content increases in gradual steps from 1 to 5 wt%. In these hybrid materials, the interfacial polarization and dielectric relaxation predominantly contributed in the dielectric permittivity and electric modulus dispersion at the lower frequencies. The detailed analysis of dielectric properties authenticates that these nanocomposites could be used as prominent biodegradable nanodielectrics for polymer nanotechnology-based eco-friendly future-generation numerous types of flexible devices/products.

Synchrotron radiation from a charge circulating around a cylinder with negative permittivity

We investigate the radiation from a charged particle rotating around a dielectric cylinder with a negative real part of dielectric permittivity. For the general case of frequency dispersion in dielectric permittivity, expressions are derived for the electric and magnetic fields and for the angular density of the radiation intensity on a given harmonic. Compared with the case of a cylinder with a positive real part of the permittivity, new interesting features arise in the nonrelativistic limit and for the radiation at small angles with respect to the cylinder axis. Another feature is the appearance of sharp narrow peaks in the angular density of the radiation intensity for large harmonics. We analytically estimate the height, width and the location of these peaks. The influence of the imaginary part of dielectric permittivity on the characteristics of the peaks is discussed. The analytical results are illustrated by numerical examples. We show that the radiation intensity on a given harmonic, integrated over the angles, can be essentially amplified by the presence of the cylinder.

Dielectric properties of liquid crystals from the thioester series with a terminal polar group

ABSTRACTThis paper presents the results of our studies of the phase transition behaviour and dielectric properties of three compounds from two series of thiobenzoates characterised by the presence of polar terminal groups. In two of the compounds (5OSCl and 6OSCl), the polar terminal substituent is −Cl, whereas the third compound (11OSNO2) has a terminal nitro group. The compound 5OSCl has an enantiotropic nematic phase N and monotropic smectic A phase and 6OSCl is characterised by the existence of two enantiotropic phases, the N and smectic A phases. The compound 11OSNO2 only exhibits an enantiotropic SmA phase. The permanent dipole moments of the studied molecules are located parallel to their long axes, which promotes the formation of SmA phase variants. The results of dielectric permittivity dispersion and absorption and spontaneous polarisation measurements allowed the SmA phase to be identified in the compounds we investigated.

Dielectric relaxation and electrical conductivity studies in (100 − x)(Li0.12Na0.88)NbO3 − xBaTiO3 (0 ≤ x ≤ 40) ferroelectric ceramics: an impedance spectroscopic analysis

Dielectric relaxation and conductivity mechanism in (100 − x)(Li0.12Na0.88)NbO3 − xBaTiO3 (0 ≤ x ≤ 40) ferroelectric ceramics were investigated using impedance spectroscopy over a broad temperature (− 100 °C to 500 °C) and frequency (0.1 Hz to 1 MHz) range. The dielectric relaxation and conductivity mechanism is considered to be associated with oxygen-defect-related complexes (VO··, ((TiNb′ − VO··)·) and ionization of oxygen vacancies (VO··), respectively. The hopping of VO·· in the lattice is considered to be equivalent to a dipolar reorientation contributing to the dielectric relaxation, whereas ionization of VO·· provides some localized electrons (e′) which further contribute to conduction mechanism at higher temperatures. Furthermore, a low-frequency dispersion in dielectric permittivity is observed, which is recognized as a quasi-DC process where the bipolar orientation or the charge carrier transition occurs naturally through discrete movements and that every orientation or transition contributes to e′ makes a proportional contribution to e″. The activation energies of DC conduction (0.64–1.24 eV) and the range of activation energies associated with the grain boundary conduction (0.72–1.22 eV) also indicate that the conduction mechanism is regulated by hopping of electrons through the grain boundary that could be associated to the oxygen vacancies.

Structural, thermal, dielectric and optical behaviour investigations of water-free ZnO/lyotropic liquid crystal nanocolloids

ABSTRACTZinc oxide (ZnO) nanoparticles of spherical symmetry (average size of ≈ 20 nm) have been synthesised via a non-aqueous lyotropic liquid crystalline (LLC) templating process. Lyotropic liquid crystalline nanocolloids are prepared via dispersing 0.05, 0.1 and 0.5 wt.% ZnO nanoparticles in non-aqueous lyotropic phase. No structural phase change has been seen with the doping of nanoparticles as stable lamellar phases are observed in all the cases. Stability of the lamellar structure and orientation of the ZnO nanoparticles in the liquid crystalline matrix may be attributed to the interfacial surface charge interactions. A significant increase and pronounced dispersion in dielectric permittivity of the ZnO/LLC nanocolloids could be the result of parallel coupling among guest/host, higher dipole- moment of the ZnO nanoparticles and Maxwell-Wagner polarisation. The variation of relaxation parameters has also been discussed and correlated with the dielectric and structural parameters. ZnO/lyotropic nanocolloids devices exhibit dc conductivity of the order of 10−5S/m owing to the increase in the number of ions (of the order of 1019m−3) in the doped systems. Nanocolloids exhibits, the refractive index of range 1.40 to 1.45 and the wide bandgap of the range 4.1–4.5 eV.

Dispersion of Dielectric Permittivity in Ferroelectric Ceramics (K0.5Na0.5)NbO3 Modified with BaTiO3

Dispersion of the dielectric constant of ferroelectric ceramics based on (K,Na)NbO3 modified by barium titanate with a concentration of 0.01, 0.02 and 0.04 mol % is studied in the temperature range of 25–120°C. Patterns in the effect the modifying additive has on the dispersion of the dielectric constant in the frequency range of 0.25–105 Hz are determined.

Dielectric properties of ferroelectric nanocomposites of nanocrystalline cellulose and sodium nitrite

A novel nanocomposite consisting of nanocrystalline cellulose (NCC) and sodium nitrite (NaNO2) was synthesized and its dielectric properties were investigated at the temperature range of 20–170 °C and at the frequency range of 10−3–106 Hz under low electric fields (1 V cm−1). The obtained results manifest a reduction in the phase transition temperature of the synthesized composite (110 °C) compared to those of bulk NaNO2 (164 °C) due to the tilting action of the depolarizing field on the polarization for NaNO2 inclusions resulting from the presence of the bound charges on their surfaces. In addition, a significant dispersion of dielectric permittivity was detected and the explanation for this was based on the Maxwell–Wagner–Sillars relaxation mechanism.

Preparation and dielectric properties of a mixed ferroelectric composite from nanoparticles of cellulose and triglycine sulfate

In this study, a novel ferroelectric composite consisting of triglycine sulfate (TGS) and cellulose nanoparticles (NCCP) prepared from waste cotton was synthesized and characterized by X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR) and Zetasizer analyzer. The study on electrophysical properties of the composite were performed from 25 to 120 ˚C under a weak electric field with an amplitude of 1 V/cm at low and infra-low frequencies (10−3 to 103 Hz) with different weight composition ratios. The obtained results indicated that the increase in cellulose concentration in the composite led to increasing the phase transition temperature in TGS component by 3 to 63 °C higher than those for single crystal TGS (+49 °C). The corresponding increase of the Curie temperature in composites was presumably connected with the strong interaction between TGS and cellulose nanoparticles through the system of hydrogen bonds. In the temperature range 100–115 °C, where the structural changes in pure triglycine sulfate were recorded earlier in the case of high-temperature annealing, a characteristic growth of the dielectric permittivity was also observed. The study on low and infra-low dispersion of dielectric permittivity was carried out and explained by Maxwell-Wagner-Sillars interfacial mechanism.

Dielectric anomalies of the PMN-PT-based multicomponent ceramics in electric fields

A study of the dielectric properties and the Barkhausen effect in the PMN-PT-based multicomponent ceramics near the morphotropic phase boundaries in electric fields was performed. It is shown that with an increase in electric field value (at E = 2.0–5.3 kV/cm), a plateau-like dielectric anomaly appears and a sharp suppression of the dielectric permittivity dispersion occurs. At the same range of E the Barkhausen jumps number and their intensities increase significantly. In addition, their shapes change from the first type to the second one. Possible reasons of observed experimental features in electric fields are discussed.