Dielectric Modulus Research Articles

Determination of self and cross contributions to the dipole–dipole correlations function from analysis of dielectric measurements

The nonexponential nature of the structural relaxation is one of the most characteristic features of the molecular dynamics in glass-forming liquids. Various experimental techniques can be employed to probe this process; however, broadband dielectric spectroscopy (BDS) is the most frequently used. Based on MD simulations, we provide strong evidence of bi-modal nature of the dielectric loss peak of primary relaxation. Further, we point out that the primary dielectric relaxation process measured at constant displacement D is dominated by the self-correlation term in the dipole–dipole correlation function. In practice, it means that the dielectric spectra should be presented in the dielectric modulus representations to disclose the spectral features of the self mode.

Effects of Ion Irradiation on Modifying Surface Characteristics and Dielectric Properties of PVA Polymeric Materials

In this work, PVA polymeric sheets were irradiated utilizing a homemade ion beam cold cathode source for use in optoelectronics applications. The PVA films were exposed to hydrogen beams with fluence range 8 × 1017 to 24 × 1017 ions.cm−2. The structural and functional group characteristics of pure and treated PVA films were investigated using XRD and FTIR methods, which confirmed the success fabrication of the PVA films. In frequency of 102 to 5 × 106 Hz, the conductivity, electrical impedance, and dielectric modulus of untreated and treated samples were determined. The dielectric characteristics of PVA films exhibit a significant modification when subjected to a hydrogen beam. Additionally, after being exposed to 16 × 1017 ions, the dielectric constant ε′ improved from 0.0078 for un-irradiated PVA to 0.0395, and conductivity changed from 8.87 × 10−11 S cm−1 to 3.32 × 10−10 S cm−1. Moreover, the relaxation time for PVA is reduced from 28.4 × 10−5 s to 8.98 × 10−5 s for 8 × 1017 ions.cm−2 and to 3.5 × 10−5 s for 24 × 1017 ions.cm−2. The present study extends the potential use of the treated PVA films to a broader range of fields, including microelectronics.

Dielectric, Conductivity and Modulus Properties of Au/ZnO/p-InP (MOS) Capacitor

Dielectric, conductivity and modulus properties of MOS capacitor with zinc oxide (ZnO) interlayer produced via RF magnetron sputtering were investigated by using admittance spectroscopy measurements. Frequency and temperature dependence of the complex dielectric permittivity (ε* = ε′-iε″), dielectric loss factor (tan δ), ac conductivity (σ ac) and complex electric modulus (M*=M”+iM’) were studied in temperature interval of 100–400 K for two frequencies (100 kHz and 500 kHz). While the dielectric constant (ε′) and loss (ε′) value increase as the temperature rises, their values decrease as the frequency rises. The increase in ε′ and ε′ is explained by thermal activation of charge carriers. Also, the σ ac value increases both frequency and temperature increase. The thermal activation energy (Ea) were determined from slope of Arrhenius plot.

The study of structural, dielectric, impedance and modulus properties of La0·8Pb0·2FeO3 doped by 25% Mg into the B-site

The sample of La0·8Pb0·2Fe0·75Mg0·25O3 was synthesized via the sol-gel route. The Refinement using the Rietveld method confirms that the structure is orthorhombic with space group Pnma. The dielectric properties (ε) and modulus (M) of the material were studied a wide range of temperatures and frequencies range. The constant dielectric values of our compound were lower than those for LaFeO3. Indeed, relatively reduced values of the dielectric constant, not exceeding 102 F/m, were usually achieved when intrinsic ionic and electronic polarization mechanisms were employed in the studied structure. Dielectric losses were described by the Giuntini theory. The imaginary modulus spectra were adjusted using the exponential function provided by Kohlrausch-Williams Watts (KWW) relaxation function, which determined the presence of thermally activated relaxation. The comparative display of the normalized impedance and electric modulus revealed the existence of short-range movement of the charge carrier. Relaxation phenomena of the non-Debye type were confirmed in the material by studying the modulus.

Structural, dielectric and electric modulus analysis of praseodymium-substituted SrPrxFe12-X O19 nanoparticles synthesized via micro-emulsion

Structural, dielectric and electric modulus analysis of praseodymium-substituted SrPrxFe12-X O19 nanoparticles synthesized via micro-emulsion

Extraction, Purification and Electrical Characterization of Gross Galactomannan and Purified Galactomannan Obtained from Adenanthera pavonina L. Seeds.

Aiming of self-sustainable production, the search for biodegradable and biocompatible materials has brought with it the need to know the physicochemical and dielectric characteristics of polysaccharide-based composite structures, which can be used as important and promising raw materials for biotechnology and electronic industries. Galactomannans are polysaccharides, extracted from seeds and microbiological sources, consisting of mannose and galactose. In this context, this work aimed to extract, purify and characterize by XRD, FTIR and impedance spectroscopy galactomannan obtained from seeds of Adenanthera pavonina L. The purification process was made with ethyl alcohol at concentrations of 70, 80 and 90 %. Polymeric films were prepared by solvent slow evaporation at low temperatures. XRD measurements revealed that Galactomannan from Adenanthera pavonina L., after purification, has a semi-crystalline structure due to the identification of two peaks the first between 5.849° and 6.118° and the second between 20.011° and 20.247°. FTIR spectra showed the functional groups associated with monosaccharides of the galactomannan from Adenanthera pavonina L. seeds, as well as the typical polysaccharide bands and peaks, confirmed by literature data. The impedance results give an increment on the state-of-the-art of this biomaterial by showing the existence of dielectric relaxations, independent of the degree of purification, using the dielectric modulus formalism. The permittivity analysis reveals the presence of water in the structure of the film, whose dipoles contribute to the relatively high value of the dielectric constant. From the results obtained, it can be concluded that purified galactomannan has the potential for possible applications in the electronics industry as a green and eco-friendly dielectric material.

Li2SO4 doped Li2O + B2O3 glasses: Hopping mechanism, relaxation phenomena and conductivity behavior

This oxide glass system work reports a detailed of the hopping mechanism, electrical conductivity, and dielectric relaxation phenomena in Li2O + B2O3-based glass for various Li2SO4 mol%. The conductivity, impedance, and dielectric modulus were analyzed in a temperature range from 363 K to 563 K and in a frequency range from 100 Hz to 5 MHz. The conductivity of the glass sample was verified using Cole-Davidson, Jonscher’s power law, and Cole-Cole models and is found to be consistent with each other. Conductivity at the grain and grain boundary was also determined by fitting the impedance data using constant phase elements (CPE) in an equivalent circuit model. The equivalent circuit was used to interpret the impedance semicircles obtained from the ac measurements. Interpretation of the relaxation mechanism in the glass matrix is described by employing Kohlrausch-William-Watts (KWW) model and the modified KWW model, which discloses that the non-Debye type relaxation mechanism is followed by the charge carriers. Impedance spectroscopy has been discussed to distinguish between the contribution of grain boundaries and grains in the relaxation mechanism. The doping Li2SO4 effect can be explained by observing activation energy in the investigated samples. The power law exponent ‘S’ for glass matrix with temperature depicts CBH and NSPT hopping mechanism in AC conductivity. All the above results reveal the glass’s semiconducting nature and depend on the lithium sulphate content in the glass matrix.

Preparation, characterization and electrical properties of 80 PEO − 20 PVdF: x NaNO3 complexed polymer electrolyte systems

PEO (Polyethylene Oxide) and PVdF (Polyvinylidene Fluoride) based Coplexed Solid Polymer Electrolytes (CSPEs) have been prepared using solution casting method with different weight percentages of NaNO3 (Sodium Nitrate). DMF (Dimethyl Formamide) was used as common solvent. The prepared systems are characterized by XRD (X-Ray Diffraction), SEM (Scanning Electron Microscopy), FTIR (Fourier Transform Infrared Spectroscopy) and DSC (Differential Scanning Calorimetry) to investigate the crystal structure, surface morphology, vibrational modes, and melting points respectively. Impedance spectroscopy is used to investigate the electrical, dielectric, and electric modulus properties of CSPE systems between temperatures of 298 K and 348 K in the frequency range of 100 Hz to 10 MHz. The ionic conductivity of polymer systems is found to increase with temperature. The maximum enhancement in conductivity (9.334x10-5 S cm−1) is observed for 5 wt% salt system, which is attributed to decrease in crystallanity and increase in the concentration of defects in space charge region formed between the host polymer and salt. Ion transport number has been calculated by using Wagner's polarization method and the maximum (0.89) is noticed for PPN-5 system.

Two Schiff base iodide compounds as iodide ion conductors showing high conductivity.

Here, we reported the crystal structures, dielectric and conducting properties of two Schiff base iodide compounds [m-BrBz-1-APy]I3 (1) and [o-FBz-1-APy]I3 (2). The Schiff base cations build irregular channel frameworks, and the polyiodide anions are located in the channel. The impedance spectra demonstrated that the two compounds show intrinsic iodide ion conductance with higher conductivity of 1.03(4) × 10-4 S cm-1 at 343 K for 1 and 4.94(3) × 10-3 S cm-1 at 353 K for 2. The dielectric modulus analysis further confirmed that the conductance contributed to the migration of iodide ions.

Improving the optical, dielectric properties and antimicrobial activity of Chitosan–PEO by GO/MWCNTs: Nanocomposites for energy storage and food packaging applications

This work is an attempt to improve the multifunctionality of chitosan–polyethylene oxide (Ch.–PEO) blend for different industrial applications including energy storage and food packaging applications. Graphene oxide (GO)/blend and multi-walled carbon nanotubes (MWCNTs)/GO/blend films were prepared by the solution casting method. FTIR analysis indicated the existence of Ch. and PEO functional groups and the positive interaction between the added nanofillers and the blend chains. XRD data confirmed interfacial compatibility between PEO and Ch. and showed that the semicrystalline nature of the blend was decreased after the incorporation of the filler. SEM analysis displayed that the blend surface is homogenous and crack-free, and the MWCNTs/GO were well-dispersed and uniformly distributed on the surface. The blend showed transmittance in the visible and NIR regions in the range of 76–91%. Loading MWCNTs/GO reduced this range and significantly increased the extinction coefficient of the blend. The indirect/direct band gap decreased from 4.3/5.2 eV to 3.0/3.8 eV with increasing fillers content. Moreover, the optical constants of the blend and nanocomposite films were determined. The dielectric measurements revealed that MWCNTs/GO doping increases the defects and results in a larger number of dipoles inside the blend and hence increases the dielectric constant of the blend. In addition, tan (δ) for all films is very small (˂ 0.05) and MWCNTs/GO/blend exhibits conductivity four times greater compared with the pure blend. The conduction mechanism, dielectric modulus, and Cole-Cole plots in the temperature range of 30–110 °C and frequencies in the range of 10−2 Hz–10 MHz were reported. The thermal analyses (TGA and DSC) for the blend and nanocomposite films were performed in the temperature range of 25–550 °C. TGA and DTG revealed three distinct weight-loss events for the samples; 25–122 °C, 229–360 °C, and 365–440 °C. The doped samples were more thermally stable where the blend lost 20% of its weight at 180.9 °C, while after doping with GO and codoping with MWCNTs, this temperature increased to 190.5 and 210.2 °C, respectively. The blend and nanocomposite solutions showed a wide antimicrobial activity against gram-positive and gram-negative bacteria, yeast, and fungi. Specifically, both GO/Ch.–PEO and 0.004%MWCNTs/GO/Ch.–PEO represented the highest antimicrobial against all tested microbes. Staphylococcus aureus ATCC 8095 was founded to be the most sensitive among the examined microbes. Additionally, the least sensitivity to studied solutions was recorded by Penicillium roqueforti. The improvements in the optical and dielectric properties make the prepared nanocomposites suitable for energy storage devices, while the antimicrobial activity suggests the use of GO/Ch.–PEO and MWCNTs/GO/Ch.–PEO nanocomposites for food packaging applications.

Electrical Properties of Jackfruit Seed Starch and Polyvinyl Alcohol Blend with Different Composition of Zinc Oxide

A biopolymer electrolyte made from natural polymer consists of jackfruit seed starch (JSS) and polyvinyl alcohol (PVA) with a different composition of zinc oxide (ZnO) was prepared using the solution casting method. The incorporation of metal oxides such as ZnO into natural polymers can improve the electrical properties, which can produce biodegradable energy storage devices. This innovation may aid in the reduction of the use of electronic devices, which generate e-waste. Thus, this study was conducted to investigate the effect of ZnO addition to the biopolymer in terms of its electrical properties. The samples were prepared by using the solution casting method. Different percentages of ZnO were mixed with JSS, PVA, hydrocloric acid, sodium hydroxide, and glycerol before being moulded in a petri dish and dried at room temperature. The electrical properties of the blends were then characterized by using an Agilent 4284a Precision LCR meter. The highest ionic conductivity value for JSS and PVA after the addition of ZnO is 1.10x10-6 Scm-1 with 10% of ZnO, and the lowest conductivity is 2.11x10-7 Scm-1 with 14% of ZnO. The dielectric and electric modulus were further studied in order to understand the electrode polarization effect.

Conductivity measurement and dielectric, impedance and modulus spectroscopic studies on bis (P-nitrophenol) melaminium monohydrate

The present work is aimed to study the dielectric and electrical characteristics of bis (P-nitrophenol) melaminium monohydrate (BNPM) over the temperature and frequency ranges of 333–453 K and 50 Hz–5 MHz, respectively. The dielectric properties such as dielectric constant (ε′), dielectric loss (ε″), ac-conductivity (σac), real (M′) and imaginary part (M″) of dielectric modulus were investigated as a function of temperature and frequency. The impedance analysis has been carried out using Cole-Cole plots to elucidate the electrical conduction mechanism. Further, observations indicated that the grain boundaries are more resistive and capacitive than the grains, inducing inhomogeneity in the material, which, in turn, causes broad frequency-dependent dielectric anomalies. The observed frequency-dependence of the AC conductivity validated the Jonscher power law. Further, an asymmetric dispersion peak in the imaginary part of the electrical modulus (M”) was noticed, indicating that the fabricated material exhibits non-Debye relaxation behavior.

Tuning the optical properties, AC conductivity and dielectric modulus of PVA membrane by inclusion of TiO2 nanoparticles

Tuning the optical properties, AC conductivity and dielectric modulus of PVA membrane by inclusion of TiO2 nanoparticles

Diverse structures and multi-step dielectric relaxation of three lead bromide hybrid crystals based on 1-aminopyridinium and its cyano-substituted Schiff bases

Oriented design of crystal structures to obtain specific properties is one of the hot topics in the field of chemistry and materials. In this paper, three organic–inorganic hybrid crystals were synthesized by the reaction of 1-aminopyridinium salts with o-, m-, and p-cyanobenzaldehyde and PbBr2. The asymmetric unit of 1 ([1- aminopyridinium][Pb2Br5], P21/m) contains half of the 1-aminopyridinium cation and the anion forms a zig-zag shaped puckered sheet of [Pb2Br5]∞; while 2 ([m-cyanobenzaldehyde-1-aminopyridinium][PbBr3], Pna21) includes a m-cyanobenzaldehyde-1-aminopyridinium Schiff base cation, and the anion forms a [PbBr3]∞ single chain. On the other hand, 3 ([p-cyanobenzaldehyde-1- aminopyridinium][PbBr3], P21/c) consists of a p-cyanobenzaldehyde-1- aminopyridinium Schiff base cation, with the anion forming a [Pb2Br6]∞ double chain. Structural analysis and energy framework calculations show that 2 possesses stronger π-π stacking and hydrogen bonding interactions, and its lattice energy and thermal stability are higher than those of 1 and 3. The combined use of CE and dielectric modulus analysis reveals a good correlation between multi-step dielectric relaxation and intermolecular forces. This strategy of modulating the crystal structure and dielectric properties by altering the position of the substituents provides useful assistance in the design of new relaxation dielectric materials.

The H+ ion transport study in polymer blends incorporated with ammonium nitrate: XRD, FTIR, and electrical characteristics

The present study gained insights into H+ ion transport through non-destructive techniques. The XRD outcome reveals that poly(2-ethyl-2-oxazoline) (POZ) reduced the crystalline phase of chitosan (CS) effectively. Films of ion-conducting polymer blend electrolytes were created from CS:POZ complexed with ammonium nitrate (NH4NO3) as an H+ supplier by using the solution casting method. X-ray diffraction was used to study the structural alterations that occurred. The degrees of crystallinity were estimated from the deconvoluted XRD pattern. Measurement of electrical impedance was carried out for the electrolytes. From FTIR measurement, free ion and ion pair values were calculated. Several ion transport parameters (ITP), such as number density (n), ionic mobility (μ), and diffusion coefficient (D), were determined. It was found that the maximum conductivity was 3.87 × 10−6 S cm−1 at 30 percent NH4NO3. The DC conductivity pattern changes linearly with temperature. Dielectric and electric modulus were studied in detail. It was discovered that the loss tangent peak transferred to a upper side of frequency when the salt concentration was increased. Long-range conductivity relaxation was seen in the Mi spectra. The lack of a full semicircle arc on the Argand figure suggested non-Debye ion dynamics. The observed AC conductivity (σac) spectra showed three different zones. In the high-frequency range, the σac value follows a power law (σac=Aωs).

Calorimetric Analysis and Dielectric Properties of Se50Te45Ge5 Chalcogenide Alloy

Abstract In this article, the amorphous structure of chalcogenide alloy Se50Te45Ge5 is confirmed by x-ray diffraction analysis with under-constrained nature. The differential scanning calorimeter study is made for the alloy at different heating rate α. The Tg and Tc of the alloy are found to increase, whereas Tm appears to decrease with increasing α. The mean activation energy for transition and crystallization are found to be around 160 and 150 kJ/mol, respectively. The fragility index is found to decrease with the increase of α. The crystals are established to grow in two dimensions within the glass network. On the other hand, the dielectric constant and loss are studied at frequencies between 30 Hz and 1 MHz and at temperatures between 20 and 300 K. The dielectric modulus of the experimental data is then analyzed using different models. Suitable fitting to the practical data is attained by the application of Davidson–Cole formalism with γ-values ranging from 0.82 to 0.99 with increasing of the temperature.

Closed-form expressions for the effective properties of piezoelastic composites reinforced with cylindrical fibers by Maxwell scheme

In this work, the Maxwell scheme is implemented to characterize the effective properties of piezoelastic fiber composites reinforced by unidirectional cylindrical fibers distributed along the x3-axis. The piezoelastic composites are assumed to have transversely isotropic constituent materials. Analytical expressions for the effective properties (elastic, piezoelectric, and dielectric) are reported. The Mori–Tanaka approach is also developed for piezoelastic composites and it is shown that their analytical results coincide with the Maxwell scheme and the effective field method. Numerical analysis and comparisons with the two-scale asymptotic homogenization method and the semi-analytical finite element method are shown and discussed. As a summary, the novelty value of this work is that the Maxwell and Mori–Tanaka schemes have been extended to heterogeneous piezoelectric structures. Closed formulas are derived for the effective elastic, piezoelectric, and dielectric moduli. A numerical implementation of the effective moduli is carried out and the overall properties are validated with other methods.

Structural, morphological, electrical, and magnetic characteristics of 20MnFe2O4-80SiO2 nanocomposite synthesized by the one-pot auto-combustion route

We report an investigation of the structural, morphological, the ac-dc electrical, magnetic, and Mössbauer spectroscopy properties of 20MnFe2O4-80SiO2 nanocomposite prepared using a one-step and facile auto-combustion approach. XRD pattern shows the formation of MnFe2O4 nanocrystallite without any crystallization of the SiO2 phase. However, the presence of a secondary phase of the nanosized α-Fe2O3 particles was also detected. The morphological analysis showed aggregation of polygonal magnetic nano-crystallites dispersed non-uniformly in a silica matrix. The dc electrical measurements performed on a wide range of temperatures from 120 to 400 K showed the semiconducting nature of the nanocomposite. The temperature dependence of dc conductivity could be perfectly fitted to the nearest neighborhood hopping model with activation energy, ΔENNH, of 0.45 eV. The Nyquist plots demonstrated a nonmonotonous thermally activated trend and non-Debye relaxation behavior. An equivalent circuit was successfully fitted to the complex impedance spectra. The variation of both grain and grain boundary conductivities as a function of temperature exhibited three distinct regions, semiconducting-metallic-semiconducting with different activation energies over the measured temperature window. The provided description of such behavior is further advocated by the ac conductivity and dielectric modulus studies. VSM measurements revealed that the nanocomposite magnetic behavior deviates from the ideal non-interacting superparamagnetic picture, due to the presence of α-Fe2O3 nanocrystalline impurities and relatively intensive exchange interactions between ions. Mössbauer spectra showed the presence of Fe3+ ions with sixfold environment and also confirmed the existence of a sextet related to α-Fe2O3 with a quantity of about 20% out of magnetic components. Fe3+ superparamagnetic doublets were also found within the fitting procedure.

Complex impedance formalism: An alternative approach for exploration of relaxation dynamics in conductive materials

A new method, the complex impedance formalism, is presented to disclose the relaxation process of conducting materials. This method is an extrapolation of the dielectric modulus formalism in the Bode representation of the impedance. As in the dielectric modulus formalism, the relaxation process can be approached in both the frequency and time domains for non-Debye relaxation type. The complex impedance formalism is tested by analysis of the relaxation process of the solid BaTiO3 material at high temperatures. A combination of complex impedance and dielectric modulus formalism provides us with a better understanding concerning individual relaxation regions. The complex impedance formalism allows the hidden relaxation process at low frequency regime to be accessible, whereas the dielectric modulus formalism discloses the relaxation process at high frequency in mixed electronic-ionic conductors.

Porous chitosan particles doped by in situ formed silver nanoparticles: Electrorheological response in silicon oil

AbstractEffect of in situ formed silver nanoparticles doping on electrorheological response of highly porous chitosan particles in suspensions of polydimethylsiloxane (silicone oil) is considered. Silver nanoparticles are directly reduced by chitosan from solution. Highly porous chitosan particles with different silver content are fabricated by spraying from solution followed by freeze‐drying. A high and stable electrorheological response of suspensions in wide range of electric field strength is observed at a very low filler content of 1 wt%. The nature of the electrorheological effect is considered from the standpoint of dielectric spectroscopy. The activation energies of polarization processes are determined from the temperature dependences of the dielectric loss modulus. The study shows the opportunity to control the properties of stimuli‐responsive materials by changing the structure and physicochemical properties of the functional filler. This approach opens up new possibilities for creating materials with high performance and predetermined properties.