Dielectric Relaxation Analysis Research Articles

Liquid-phase synthesis of a Li3PS4 solid electrolyte using ethyl isobutyrate as a synthetic medium

A β-Li3PS4 solid electrolyte was prepared via liquid-phase synthesis using ethyl isobutyrate as a synthetic medium. The precursor and solid electrolyte structures were characterized using thermogravimetry–differential thermal analysis and X-ray diffraction techniques. The dielectric relaxation analysis showed two relaxation regions, which revealed a bulk and grain boundary ionic migration process. At a temperature lower than 90°C, the frequency dependence of the dielectric constant of the prepared sample was different from that of glassy Li3PS4, indicating that the motion of the PS4 unit enhances the ionic conductivity of the Li3PS4 solid electrolyte. The ionic conductivities of the cold-pressed and warm-pressed pellets at 25°C were 6.8 × 10−5 Scm−1 and 3.6 × 10−4 Scm−1, respectively.

Dielectric relaxation and electrical conductivity in lead-free organic ferroelectric diisopropylammonium bromide (dipaBr)

In this communication, we explore the dielectric relaxation behavior of the novel organic salt Diisopropylammonium Bromide (dipaBr), focusing on the universal relaxation law. We conduct dielectric relaxation and conductivity analyses across a broad spectrum of temperatures (325K–443K) and frequencies (20 Hz–20 MHz). The irregularity in peak broadening observed in complex modulus spectroscopy indicates a distribution of relaxation periods with varying time constants, confirming that the relaxation is of the non-Debye type. To interpret the experimental findings, we utilize the Havriliak-Negami (HN) formula in our investigation of dielectric relaxation. The parameters derived from the model are discussed. The relaxation process in the material appears to depend on temperature. The ac conductivity profile follows Jonscher's universal power law, and the relationship between bulk DC conductivity and temperature follows an Arrhenius-like pattern.

Enhanced permittivity of Lu-doped SrTiO3 ceramics sintered in air atmosphere through defect chemistry

A series of Sr1‒1.5xLuxTiO3 (x = 0, 0.005, 0.01, 0.015, and 0.02) ceramics was sintered under an air atmosphere through the solid-state reaction method. The results show that doping with Lu3+ considerably enhances material permittivity. The ceramic with x = 0.01 exhibits a colossal permittivity (CP) of ∼101000 with a tanδ of ∼0.16 at a frequency of 1 kHz, demonstrating enhanced stability over a wide temperature (30 to 300 °C) and frequency (102 to 106 Hz) range. Based on the analysis of dielectric relaxation, X-ray photoelectron spectroscopy (XPS), and the universal dielectric response law, the CP effect is primarily due to the formation of defect dipoles, which are correlated with the presence of oxygen vacancies, such as Ti3+ Ti3+, , Ti3+, and Ti3+. These defect dipoles serve to pin electrons, limiting long-range transitions, and enhancing local polarization. Doping with Lu3+ also induces a secondary Lu2Ti2O7 phase, which are characterized by X-ray diffraction (XRD) and energy-dispersive X-ray spectroscopy (EDS). The results generated in this study can inform the development and application of new CP materials based on SrTiO3.

Development of a lead-free colossal dielectric material barium bismuth ferrous oxide for electronic devices

Ceramic materials are promising for the ever-increasing demand in next-generation electronic devices. In this regard, we report the development and characterizations (structural, microstructural surface, dielectric, transport, impedance, resistive and current-voltage properties) of a novel complex material Ba3Bi2Fe2O9. Preliminary investigation of the X-ray diffraction (XRD) pattern shows the dual phase nature (cubic and tetragonal phase). The analysis of the Williamson-Hall plot illustrates the average crystallite size and micro-lattice strain are 91.37 nm and 0.002, respectively. The scanning electron microscopic spectrum examines the microstructural surface interface analysis, fractal study and topographic roughness (using the standard ISO25178). The analysis of Maxwell-Wagner dielectric dispersion, relaxation, and transport mechanisms are investigated utilizing dielectric, impedance, and conductivity spectrum accumulated within the experimental frequency (1 kHz–1 MHz) and temperature (298 K–373 K) range. The energy band of intrinsic and ionization regions with different frequencies (1 kHz and 10 kHz) indicates the semiconducting behavior of the material. The presence of non-Ohmic and space charge limited conduction (SCLC) mechanisms is investigated by the varistor constant β1 and β2. The thermistor constant (β) is determined to be 1683.13, and the temperature coefficient of resistance (TCR) is −0.00903, which may be suitable for wearable NTC thermistors and other related device applications.

The molecular dynamics during gelation of resorcinol and formaldehyde as studied by dielectric relaxation

The gelation of resorcinol and formaldehyde (RF) consists of four secondary processes with no well-defined time boundaries. The growth kinetics of RF gel processes are still many unknown areas. In this work, the sol-gel polycondensation reaction of RF was analyzed by dynamic light scattering (DLS), rheological measurements, and dielectric relaxation spectroscopy (DRS). Through in situ analysis, some molecular dynamics information of RF gelation was obtained, such as particle size change trend, gel threshold time, dipole moment change and so on. These molecular dynamics information reflects the effect of the concentration of the RF reaction solution on the growth process. That is, the low-density RF sol is in the nucleation-dominant mode, while the high-density RF sol is in the diffusion-dominant mode, rapidly forming a thick skeleton. The dielectric relaxation analysis of the RF gel process included some dipole relaxations and the interfacial relaxation. The changing trend of the interfacial relaxation was consistent with the two growth modes obtained from the rheological measurements. By analyzing the kinetics of the RF reaction solution at different growth temperatures, we obtained how to control the temperature to obtain stable RF gels. A nucleation-dominant mode was obtained for the initial growth at low temperature, followed by a diffusion-dominant mode at high temperature after the gel threshold time.

The dielectric relaxation and impedance spectroscopy analysis of (Bi0.5Na0.5)TiO3-based ceramics

0.75(Na0.5Bi0.5)TiO3–0.25SrTiO3–xNb2O5 (labeled as NBT–ST–xNb, x=0.00, 0.01, 0.02, 0.03) ceramics were prepared by a solid-state reaction method. The crystal structure and grain morphology were characterized. Dielectric constant (εr) and dielectric loss tangent (tanδ) could be observed in the dielectric spectroscopy and the modified Curie-Weiss law was used to analyze the relaxation behavior. According to the impedance spectroscopy, we used the equivalent circuit model to fit the impedance results. To better understand the relaxor behavior, the electric modulus was analyzed and indicated that there was a conduction process of charge carriers from long-range mobility to short-range mobility. The relaxation activation energy (Ea) and conductance activation energy (Ec) confirmed the oxygen vacancies (OVs) also played a significant role in the conduction process.

Studies of Circuit Design, Structural, Relaxation and Potential Stability of Polymer Blend Electrolyte Membranes Based on PVA:MC Impregnated with NH4I Salt.

This work presents the fabrication of polymer electrolyte membranes (PEMs) that are made of polyvinyl alcohol-methylcellulose (PVA-MC) doped with various amounts of ammonium iodide (NH4I). The structural and electrical properties of the polymer blend electrolyte were performed via the acquisition of Fourier Transform Infrared (FTIR) and electrical impedance spectroscopy (EIS), respectively. The interaction among the components of the electrolyte was confirmed via the FTIR approach. Electrical impedance spectroscopy (EIS) showed that the whole conductivity of complexes of PVA-MC was increased beyond the addition of NH4I. The application of EEC modeling on experimental data of EIS was helpful to calculate the ion transport parameters and detect the circuit elements of the films. The sample containing 40 wt.% of NH4I salt exhibited maximum ionic conductivity (7.01 × 10−8) S cm−1 at room temperature. The conductivity behaviors were further emphasized from the dielectric study. The dielectric constant, ε’ and loss, ε’’ values were recorded at high values within the low-frequency region. The peak appearance of the dielectric relaxation analysis verified the non-Debye type of relaxation mechanism was clarified via the peak appearance of the dielectric relaxation. For further confirmation, the transference number measurement (TNM) of the PVA-MC-NH4I electrolyte was analyzed in which ions were primarily entities for the charge transfer process. The linear sweep voltammetry (LSV) shows a relatively electrochemically stable electrolyte where the voltage was swept linearly up to 1.6 V. Finally, the sample with maximum conductivity, ion dominance of tion and relatively wide breakdown voltage were found to be 0.88 and 1.6 V, respectively. As the ions are the majority charge carrier, this polymer electrolyte could be considered as a promising candidate to be used in electrochemical energy storage devices for example electrochemical double-layer capacitor (EDLC) device.

Visualizing Non-Covalent interactions between Propylamine and 2-Chlorobenzyl alcohol in Benzene: Theoretical and Dielectric relaxation studies

The non-covalent interactions of propylamine (pa) with 2-chlorobenzyl alcohol (2cbOH) in benzene have been studied by theoretical and dielectric relaxation studies. In the theoretical method, the optimized structure of pa2cbOH is achieved by the DFT method in B3LYP/6-311++G (d,p) basis set at ground level d,p orbitals. The Vibrational energy distribution analysis is adopted to find the vibrational assignment of pa2cbOH, as well as it compared with the experimental observations. Stability, electronic effects are determined through the chemical reactivity parameters with the help of FMO analysis. The hydrogen bonding and Vander Waals interactions of pa2cbOH are confirmed with reduced density gradient (RDG) isosurface. In Dielectric relaxation analysis, various dielectric parameters like ε′, ε″, ε0 and ε∞ were determined for five different mole ratios of pa2cbOH. Higasi’s single frequency equation and Gopalakrishna’s single frequency concentration variation methods are validated by measuring the multiple relaxation time τ1 and relaxation time τ2 for group rotation of pa2cbOH. The strength of hydrogen bonding and other weak interactions were determined using the values τ1 and τ2.

Dielectric relaxation and FTIR analysis of 2-chlorobenzoic acid with aniline and n-methyl aniline in 1,4-dioxane

Microwave absorption and FTIR studies of hydrogen-bonded complexes of 2-chlorobenzoic acid (2-CBA) with aniline (AN) and n-methyl aniline (NMA) in 1,4-dioxane at a 1:1 mol ratio have been carried out. For a fixed microwave frequency (i.e., 9.43 GHz), various dielectric parameter dielectric constant ε′, loss ε″ and static constants ε0, ε∞ at zero and very high frequency have been determined. Higasi et.al, equation validates the molecular association of title molecules through the relaxation time. On the 1:1 mol ratio, the values of relaxation time are observed maximum due to the complex formation. The FTIR spectra were recorded in the liquid phase, the prominent functional groups of the molecules and their corresponding shifts due to molecular associations are studied and the vibrational modes are determined theoretically by B3LYP/6–311++ at the ground state. It confirms the intermolecular hydrogen bond length and supported the dielectric relaxation analysis.

Changes in structural and dielectric properties of nontronite caused by heating

The study was focused on changes in the electrical and structural parameters of nontronite as a function of temperature in the range of 25 °C–325 °C. Nontronite during heating loses water from the interlayer space. Structural changes in the mineral were monitored by X–ray powder diffraction, thermal analysis, and dielectric spectroscopy. The experiments showed that between 35 °C–60 °C the mineral loses only a small part of water bound between the layers. This resulted in a significant change in the distance between the layers from 15.2 Å to 13.0 Å and a 100% increase in low–frequency electric permittivity. The main process of losing interlayer water molecules starts at 60 °C and finishes close to 160 °C. Interlayer water responds to the external electric field, causing an increase in electric permittivity. Analysis of dielectric relaxation gave valuable insight into the dynamics of weakly bound interlayer molecules–water in the case of natural nontronite.

Dielectric Properties of Jute Fibers Reinforced Poly(lactic acid)/Poly(butylene succinate) Blend Matrix

Dielectric measurements were performed on Poly(lactic acid) (PLA) polymer, Poly(lactic acid)/Poly(butylene succinate) (PLA/PBS) blend matrix and its green composite reinforced with Jute fibers in temperature range from 20 to 140 °C and frequency range from 10−1 Hz to 1 MHz. Thermal analyses based on differential scanning calorimetry technique have evidenced different thermal transitions of the semi-crystalline polymer occurred for PLA one. Addition of PBS into PLA polymer enhanced its crystallinity. However, the presence of Jute fibers in the green composite material lowered such effect and increased the PLA polymer glass transition temperature, Tg. These could be attributed to the PBS contribution into the Jute fibers/blend matrix interactions. Accordingly, dielectric analyses have revealed the presence of three relaxation processes for PLA polymer. These were identified to the α mode relaxation, the dc conductivity effect and the Maxwell–Wagner–Sillars (MWS) interfacial polarization effect. The latter effect was attributed to the accumulation of charges at the crystalline phase/amorphous phase interfaces of PLA polymer. Two additional dielectric relaxations appeared for PLA/PBS blend matrix. These were associated with β relaxation and interfacial polarization effect originating from PLA polymer and the semi-crystalline character of PBS polymer, respectively. The incorporation of Jute fibers into the PLA/PBS blend matrix gave rise to other dielectric relaxations associated with the water dipoles and interfacial (Jute fibers/blend matrix) polarization effects. Analysis of dielectric relaxations at high temperature above the glass transition temperature using the Havriliak–Negami model allowed probing Jute fibers/blend matrix interactions. Adhesion mechanism occurred in the studied green composite was determined by vibrational analysis based on FT-IR technique.

Existence of nearest-neighbor and variable range hopping in Pr2ZnMnO6 oxygen-intercalated pseudocapacitor electrode

The X-ray diffraction pattern and Raman spectrum authenticate the monoclinic P21/n structure of polycrystalline Pr2ZnMnO6 (PZM) synthesized by the solid-state reaction technique. The X-ray photoemission spectrum suggests the existence of oxygen vacancy in PZM, which plays a crucial role in electrical conduction as well as in electrochemical behavior. The existence of two different conduction mechanisms (such as nearest-neighbor hopping (NNH) and Mott's variable range hopping (MVRH)) is observed from the investigation of dc conductivity studies, dielectric relaxation, and impedance analysis of PZM. It is found that below 580 K, there is a transition from NNH to MVRH due to the decrease of activation energy. The constant phase element model is used to correlate the Nyquist plot and electric modulus of PZM. The bulk PZM electrode exhibits intercalated pseudocapacitive nature which offers an efficient specific capacitance of 69.14 F/g at a charge and discharge currents of 2 A/g in an aqueous solution of 1 M KOH. The charge storage mechanism of the PZM electrode has been analyzed and discussed.

Experimental and computational investigation of PVDF–$$\hbox {BaTiO}_{{3}}$$ interface for impact sensing and energy harvesting applications

The interfacial polarization between PVDF and $$\hbox {BaTiO}_{{3}}$$ was studied using density functional theory calculations and atomic charge density analysis. A comparative study of dielectric relaxation, thermodynamic properties and impact analysis of the electrospun polyvinylidene fluoride (PVDF) and a 3 $$\%$$ $$\hbox {BaTiO}_{{3}}$$ –PVDF nanofibrous composite are presented. The frequency-dependent dielectric properties revealed the microstructural feature of the composite material. The impedance analysis and Nyquist plots showed a decrease in the bulk resistance of the composite compared to the pure PVDF. The temperature dependence of the electric modulus shows Arrhenius-type behavior. The electric loss modulus relaxation peak shifts towards the high frequency side which indicates a decrease in relaxation time and faster charge carrier dynamics. The observed non-Debye type dielectric relaxation in electric loss modulus follows a thermally activated process, which can be attributed to the polaron hopping effect. The particle-induced crystallization of the PVDF polymer is supported by thermodynamic properties from differential scanning calorimetric measurements. The observed increase in piezoelectric response from high strain rate impact sensing was attributed to the interfacial interaction between PVDF and $$\hbox {BaTiO}_{{3}}$$ .

Quantitative and qualitative analysis of segmental dielectric relaxations and space charge by TSDC in nanocomposites of natural rubber/clay

The effect of adding three different layered clays, a sodium montmorillonite and two commercial modified montmorillonites, on the morphology and molecular dynamics of natural rubber characterized by Transmission Electron Microscopy and Thermally Stimulated Depolarization Currents (TSDC) was studied. Carbon black was employed as reinforcing filler in a standard compound prepared and used for comparison purposes. The morphological results revealed that the sample with Cloisite\circledR 15A displays the highest degree of exfoliation, which suggests a stronger compatibility between the organic and inorganic phases. When the dispersion degree increases, a decrease of the activation energy was found from the quantitative analysis of the space charge dielectric relaxations. From the qualitative analysis of the dipolar dielectric relaxations around $T_{g}$, changes in the dielectric relaxation profile and in the peak localization were attributed to probable interactions between the nanofillers and the elastomer in the glass transition region of the NR.

A Cole‐Cole Dielectric Relaxation Analysis of Albumin and γ‐Globulins for Protein Quantification by Electrical Impedance Spectroscopy

AbstractOptimal serum protein concentrations are vital for normal body functioning. Affordable while accurate protein quantification methods with minimum processing requirements are needed for diagnosis of related diseases. The standard automated chemistry analyzer is limited by high installation and maintenance costs. This study proposes the use of electrical impedimetric spectroscopy (EIS) as an alternative to current methods. Its practical applicability was tested using albumin and γ‐globulin or their miscellanea in three different media; water, serum and tissue‐mimicking phantoms at 25 °C. Impedance measurements were taken between frequency f=0.10 MHz to 300 MHz by an impedance analyzer. A Cole‐Cole analysis was used to elucidate the stepwise variations in the dielectric parameters of the protein medium so as to obtain empirical dielectric parameter‐protein concentration relationships and their correlation coefficients R2. From the results, linear relationships between parameters and protein concentrations with high correlation coefficients over R2=0.90 were observed. Resistance to charge transfer Rct and characteristic frequency fc were significantly altered by changing protein concentrations as compared to bulk solution resistance Rs, relaxation time constant τ and shape factor α. The relationships developed would aid in monitoring changes in body fluid protein concentrations by EIS.

Unravelling ionic speciation and hydration structure of Fe(III/II) redox couples for thermoelectrochemical cells

Thermoelectrochemical cells (TECs) are promising devices for harvesting heat waste, but their widespread use has been hindered by their low thermopower densities. High-power TECs require an electrolyte solution that exhibits both high Seebeck coefficient (Se) and high ionic conductivity; thus far, this has been a challenge. Recently, we demonstrated that proper selection of the counter anion of Fe(III)/(II) salts can resolve the aforementioned issue, that n-type (positive Se) TECs employing the Fe(III)/(II) perchlorate redox couple display unprecedented high areal power densities compared to TECs employing Fe(III)/(II) chloride or Fe(III)/(II) sulfate couple. Herein, we unravel that the excellent performance of the Fe(III)/(II) perchlorate is ascribed to the non-coordinating nature of its perchlorate anion, which suppresses the formation of the ion pairs that reduce the Se and ionic conductivity. UV–Vis and dielectric relaxation analysis revealed that the redox reaction of the hexa aquo complexes (Fe(H2O)63+/2+), formed Fe(III)/(II) perchlorate, is accompanied by a hydration-number change larger than those of anion-coordinated species, which are dominant in chloride or sulfate media. In addition, n-type TECs can be combined in-series with p-type (negative Se) TECs to provide output powers high enough for practical application.

Molecular interactions between the mixtures of ethyl, propyl amines and 2-nitrobenzoic acid in 1,4-dioxane by DFT and dielectric relaxation analysis

Molecular interactions between ethylamine, propylamine and 2-nitrobenzoic acid in a solvent 1,4-dioxane have been studied by DFT and Dielectric relaxation analyses. In the DFT method, the vibrational assignments are performed. Molecular structures are optimized theoretically, FMO, molecular surfaces and the values of Mulliken charges were obtained by the DFT method with B3LYP/6-311++G(d,p) basis set. The charge transfers in the molecules are confirmed by the HOMO and lowest LUMO. Different dielectric parameters like dielectric constant ε', dielectric loss ε″ at microwave frequency, static dielectric constant ε0 and dielectric constant ε∞ at optical frequency were determined over five different molar ratios (i.e., 1:3, 1:2, 1:1, 2:1, 3:1). Higasi’s methods single-frequency equation and Gopalakrishna’s single-frequency concentration variation methods are validated to measure multiple relaxation time τ1 to find the strength of hydrogen bonding, whereas the relaxation time τ2 for group rotation is used to find the steric interaction of proton donor. The values of relaxation time were found maximum at 1:1 (molar ratio) of ethylamine, propylamine with 2-nitrobenzoic acid.

Molecular Interaction Studies between Methylamine and 2-Nitrobenzoic Acid by Quantum Chemical Calculation (FT-IR, FMO, GCRD, MEP, NLO) and Dielectric Relaxation Analysis

Molecular Interaction Studies between Methylamine and 2-Nitrobenzoic Acid by Quantum Chemical Calculation (FT-IR, FMO, GCRD, MEP, NLO) and Dielectric Relaxation Analysis

Thermal properties and electric modulus approach to the analysis of dielectric relaxation of nanocomposites based on carbon dots

AbstractThe investigation of thermal and dielectric properties of carbon dots dispersed in PMMA has been conducted in freestanding thin solid films. Thermal properties were studied using differential scanning calorimetry. Impedance spectroscopy, in the frequency range 100 Hz to 100 kHz and temperatures between 200 and 390 K, was used for the electrical characterization. Using the electric modulus formalism, it has been found that the Havriliak‐Negami model of dielectric relaxation is adequate to fit the experimental data, from which the relaxation parameters can be calculated. The inclusion of C‐Dots in PMMA provides a plasticizing effect on the polymer structure, giving rise to an increase in the mobility of PMMA chains, and consequent changes in the relaxation parameters.

Branching function of terminal phosphate groups of polyisoprene chain

The branching structure formed by α terminal of natural rubber (NR) was believed to be critical for its superior mechanical properties. However, it is challenging to unravel and mimic the relationship between the terminal structures and properties of NR due to the complexity of the system. Herein we synthesized a model compound containing phosphate groups at the end of the polyisoprene rubber to explore the role of α-terminal. After a series of tests, it is found that the phosphate groups formed branching points with or without iron ions. TEM test showed that sizes of aggregates formed by phosphate groups changed to be smaller after addition of FeCl3. Water contact angle test verify the formation of branching structures. Rheology test showed that branching structures increased their storage modulus G’ compared to linear polymer. The effects of phosphate groups aggregations on the chain dynamics were also investigated. Dielectric relaxation analysis indicated that the branching structure formed by phosphate groups confined the chain movement. All the above results help us to get a deeper understanding on the structural formation and function about α-terminal groups of NR.