Complex Electric Modulus Research Articles

Role of oxygen vacancy on the electrical properties of SnO2-Zn2SnO4 ceramic composites with the introduction of Nb2O5 oxide

In this work, the role of oxygen vacancy on the electrical properties of traditionally prepared SnO2-Zn2SnO4 ceramic composites was evaluated by introducing Nb2O5 oxide. With increasing Nb2O5 content, the breakdown electric field E1.0 and the relative permittivity εr measured at low frequencies increased and declined, respectively. In the microstructure photos, the grain size decreased before reaching a saturation point. In addition, Nb was randomly distributed in the grains and along grain boundaries. By doping Nb2O5, the color of the sintered samples darkened, and F-type color centers were generated. In the complex electric modulus spectra, the peak of the imaginary part M″ shifted toward a lower frequency; whereas, the activation energy Ea changed slightly with increasing Nb2O5 content. The results suggest that oxygen vacancy is the origin of the varistor and high permittivity properties of SnO2-Zn2SnO4 ceramic composites. Furthermore, the varistor and dielectric properties can be modulated by changes in the microstructure.

Impedance properties and comparison effects of different dose safranin doped hydrogels

Frequency evolution of dielectric characteristics of different dose safranin (SR) doped hydrogels was studied by impedance spectroscopy (IS) at room temperature (RT). Real and imaginary parts of complex dielectric constant, impedance, electric modulus and conductivity of SR doped hydrogels were analyzed in the frequency range of 100Hz to 40MHz for pH5.0 value. Phase angle, capacitance, surface resistivity, tangent factor (tan δ) for all samples were recorded with the same frequency range. Surface and bulk polarization effects were dominant on impedance at low and high frequency regime, respectively. Fluctuation effect of SR doped hydrogels was observed from the dielectric measurements. Tutorial of radio frequency, RF, impedance matching were realized by using the Smith chart. The coulomb interaction between SR-cations and hydrogels may be anticipated to enhance the organic electrical performance. The potential applications of SR doped hydrogels were presented to microbial fuel cells.

Effect of pH on the electrical properties and conducting mechanism of SnO2 nanoparticles

Semiconductor nanoparticles have attracted more interests because of their size-dependent optical and electrical properties.SnO2 is an oxygen-deficient n-type semiconductor with a wide band gap of 3.6eV (300K). It has many remarkable applications as sensors, catalysts, transparent conducting electrodes, anode material for rechargeable Li- ion batteries and optoelectronic devices. In the present work, the role of pH in determining the electrical and dielectric properties of SnO2 nanoparticles has been studied as a function of temperature ranging from Room temperature (RT) to 114°C in the frequency range of 7MHz to 50mHz using impedance spectroscopic technique. The non linear behavior observed in the thermal dependence of the conductance of SnO2 nanoparticles is explained by means of the surface property of SnO2 nanoparticles where proton hopping mechanism is dealt with. Jonscher's power law has been fitted for the conductance spectra and the frequency exponent (“s” value) gives an insight about the ac conducting mechanism. The temperature dependence of electrical relaxation phenomenon in the material has been observed. The complex electric modulus analysis indicates the possibility of hopping conduction mechanism in the system with non-exponential type of conductivity relaxation.

Synthesis, dielectric, conductivity and magnetic studies of LiNi1/3Co1/3Mn(1/3)−xAlxO2 (x = 0.0, 0.02, 0.04 and 0.06) for cathode materials of lithium-ion batteries

Layered structure cathode materials LiNi1/3Co1/3Mn(1/3)−xAlxO2 (x=0.0, 0.02, 0.04 and 0.06) are prepared by the sol-gel method by adding citric acid as chelating agent. The physical, electrical and magnetic properties of the synthesized materials are systematically discussed using the structural (XRD, FESEM with EDS and FT-IR), impedance (LCR) and electron spin resonance (ESR) measurements. The X-ray diffraction pattern of the synthesized samples possessed the α-NaFeO2 structure of the space group, R3¯m, with no evidence of any impurities. The peak intensity ratio I(104)/I(003) increased with Al concentration, which indicated the cation mixing between transition metal layer and lithium layer. The field effect scanning electron microscopy showed the particle size distribution in the range of 230–250nm and EDS has been analysed for elemental mapping. The local structure is investigated by vibrational spectroscopy in FT-IR study. The impedance studies are characterized by complex impedance spectroscopy (CIS) in the frequency range from 42Hz to 1MHz at room temperature (30°C). The dielectric properties are analyzed in the framework of complex dielectric permittivity and formalism of the complex electric modulus. For these samples, the ESR analysis of magnetic measurements, the degree of cation mixing, is estimated to be Ni2+(3b)=2.75%.

Structural, dielectric and a.c. conductivity study of Sb2O3 thin film obtained by thermal oxidation of Sb2S3

This work highlights some physical properties of Sb2O3 thin films obtained through heat treatment of Sb2S3 thin films under an atmospheric pressure at 400°C. The obtained material is characterized by X-ray diffraction and impedance spectroscopy. X-ray diffraction analysis shows that Sb2O3 thin films were crystallized in cubic structure having a preferential growth along (222) plane. The grain size is found to be around 65 nm. The electrical conductivity was studied using impedance spectroscopy technique in the frequency range from 5 Hz to 13 MHz at temperatures lying in 638–698 K domain. Besides, the frequency and temperature dependence of the complex impedance, a.c. conductivity and complex electric modulus have been investigated.

Effect of Au8+ irradiation on Ni/n-GaP Schottky diode: Its influence on interface state density and relaxation time

The in-situ capacitance-frequency and conductance-frequency measurements of 100MeV Au8+ swift heavy ion irradiated Ni/n-GaP Schottky structure at a constant bias voltage have been carried out in the frequency range 1kHz–1MHz at room temperature. The interface states density and the relaxation time of the charge carriers have been calculated from Nicollian and Brews method. Various dielectric parameters such as dielectric constant, dielectric loss, loss tangent, series resistance, ac conductivity, real and imaginary parts of electric modulus have been extracted and analyzed under complex permittivity and complex electric modulus formalisms. The capacitance and conductance characteristics are found to exhibit complex behaviors at lower frequency region (1–20kHz) for all the samples. The observed peaks and dips at low frequency region are attributed to the relaxation mechanisms of charge carriers and the interface or dipolar polarization at the interface. The dielectric properties are found to be effectively changed by the ion fluence which is attributed to the variation in interface states density and their relaxation time.

Superior high-temperature dielectric properties of dicyclopentadiene resin

Complex permittivity ( ϵr' and ϵr) and conductivity were measured in a wide temperature range for dicyclopentadiene (DCP) resin and epoxy resin, which show glass transition at a similar temperature around 150 °C. Furthermore, space charge distributions remaining in the two resins that had been polarized in the same wide temperature range were measured at room temperature. As a result, it was found that ϵr ’, ϵ r”, and conductivity are much lower in DCP resin than in epoxy resin at almost all the temperatures and frequencies. A further analysis using complex electric modulus, which is the inverse of the complex permittivity, indicates that charge transport is much more difficult in DCP resin. Furthermore, while similar small amounts of homocharges appear in DCP resin at any polarization temperatures, a significant accumulation of heterocharges, most likely due to ions, is induced in epoxy resin in the vicinity of the cathode/sample interface at polarization temperatures above the glass transition temperature. These results indicate that DCP resin possesses superior stable dielectric behavior, especially at high temperatures.

Varistor and dielectric properties of SiO2 doped SnO2-Zn2SnO4 ceramic composites

In this work, SiO2 doped SnO2-Zn2SnO4 ceramic composites with excellent varistor and dielectric properties were prepared through traditional ceramic processing. The obtained nonlinear coefficient α was as high as 9.6, and the breakdown electrical field EB and leakage current density JL was as low as 5.9V/mm and 62μA/cm2, respectively. At a low frequency of 40Hz, the relative permittivity εr measured at room temperature was higher than 2.5×104. The nonlinear decrease of the semicircle diameter in the complex impedance spectra with increasing DC bias voltage indicates that the grain boundary effect is an important origin of the varistor and giant permittivity properties. With an increase of temperature, the relaxor peak of the imaginary part M″ of the complex electric modulus shifted to high frequency and the activation energy Ea obtained from the M″ spectrum was about 0.31eV, much lower than the grain boundary barrier height ϕb. The results suggest that other mechanisms may also be responsible for the giant permittivity property besides grain boundary barriers.

Microstructure and charge carrier dynamics in Pr-Sm-Eu triple-doped nanoceria

In this work, microstructural, charge carrier dynamics and dielectric relaxation properties of triple rare earth (Praseodymium, Samarium and Europium) doped ceria nanomaterials have been investigated. The microstructural investigation of the compositions has been done using Rietveld analysis of X-Ray Diffraction data. The total conductivity was found to depend on oxygen vacancy, dopant vacancy interaction and charge carrier concentration. The highest ionic conductivity was obtained for the composition containing Pr=0.15 and Sm/Eu=0.075. The temperature dependence of conductivity was found to follow the Vogel–Tammann–Fulcher (VTF) relation. The complex dielectric permittivity and electric modulus have been investigated using Havriliak–Negami function. The shape parameters obtained from modulus spectra and the frequency exponent obtained from conductivity spectra were found to be slightly temperature dependent. The small polaron hopping in localized states and correlated barrier hopping conduction mechanism were confirmed from complex conductivity data. The temperature independent nature of conductivity and relaxation mechanism was confirmed from master plots of modulus and conductivity spectra. The reciprocal temperature dependence of the relaxation times obtained from electrical properties was also found to follow VTF relation.

Dielectric properties of polyamide 12-chromium(III) oxide nanocomposites

Broadband dielectric spectroscopy was employed to study polymer nanocomposites based on PA12 filled with of nanosized chromium(III) oxide. The experimental dielectric data were analyzed within the formalisms of complex permittivity and electric modulus. Three relaxation processes and Maxwell-Wagner-Sillars (MWS) interfacial polarizations were observed. It was found that presence of nanosized amphoteric chromium(III) oxide leads to softening of polyamide matrix that manifested in decrease of the activation energy of the α- and β-relaxation processes and glass transition temperatures. The softening of polymer matrix is the reason of the decrease of mechanical strength of polymer nanocomposites as compared with neat PA12.

Analysis of complex impedance of p-CuIn3Se5 by impedance spectroscopy

Both complex impedance and electric modulus formalisms are considered to study the contribution of dominant electrical conduction mechanisms in bulk p-type CuIn3Se5 semiconductor. An equivalent electrical circuit has been proposed to explain the impedance results that show semicircle arcs at different temperatures. Two different conduction mechanisms were obtained by fitting the data to Cole-Cole equation. The values of calculated resistances for the “grain” and “grain-boundary” contributions were found to decrease with increasing temperature, in agreement with the Arrhenius law associated with activation energy of 179 meV and 199 meV for the “grain” and “grain-boundary” conduction, respectively. The activation energies for relaxation mechanisms were estimated and compared with those obtained from the analysis of electric modulus.

Microstructures, electrical behavior and energy-storage properties of Ba0.06Na0.47Bi0.47TiO3-Ln1/3NbO3 (Ln = La, Nd, Sm) ceramics

The microstructures and electrical properties of a series of (1-x)Ba0.06Na0.47- Bi0.47TiO3-xLn1/3NbO3(Ln = La, Nd and Sm) ceramics prepared by the conventional solid-state reaction method were investigated. The XRD analysis revealed that all the investigated ceramics have a pure perovskite structure. A maximum energy storage density up to 1.239 J/cm3 at 100 kV/cm was exhibited for 0.98Ba0.06Na0.47Bi0.47TiO3- 0.02Sm1/3NbO3 ceramics. The activation energies of carrier migration and relaxation process in the ceramics showed nearly similar values of ∼1.0eV. The diffusion factor γ corresponding to Ln = La, Nd and Sm at a frequency of 100 kHz were estimated to be 1.96, 1.89 and 1.91, respectively. Detailed studies on dielectric spectroscopy revealed a relaxor behavior with diffuse phase transition in these ceramic systems. The general approach to equivalent circuit model of BNBT-xLnN ceramics has been used to interpret spectra obtained from impedance measurements. By additional use of the complex electric modulus formalism to analyze the same impedance data, the dispersion behavior and temperature-dependent relaxation processes of the ceramics may be probed.

Electric properties of carbon nano-onion/polyaniline composites: a combined electric modulus and ac conductivity study

The complex electric modulus and the ac conductivity of carbon nano-onion/polyaniline composites were studied from 1 mHz to 1 MHz at isothermal conditions ranging from 15 K to room temperature. The temperature dependence of the electric modulus and the dc conductivity analyses indicate a couple of hopping mechanisms. The distinction between thermally activated processes and the determination of cross-over temperature were achieved by exploring the temperature dependence of the fractional exponent of the dispersive ac conductivity and the bifurcation of the scaled ac conductivity isotherms. The results are analyzed by combining the granular metal model (inter-grain charge tunneling of extended electron states located within mesoscopic highly conducting polyaniline grains) and a 3D Mott variable range hopping model (phonon assisted tunneling within the carbon nano-onions and clusters).

Structural and conductivity studies of LiNi0.5Mn0.5O2cathode materials for lithium-ion batteries

AbstractLayered oxide LiMO2(Ni, Co, Mn) have been proposed as cathode materials for lithium-ion batteries. Mainly LiNiO2is accepted as an attractive cathode material because of its various advantages such as low cost, high discharge capacity, good reversibility. The LiNi0.5Mn0.5O2powders are synthesized by a sol-gel method using citric acid as a chelating agent. The structure of the synthesized material is analyzed by using XRD, FT-IR and the microstructures of the samples are observed by using FESEM. The intensities and positions of the peaks are in a good agreement with the previous results. The morphological changes are clearly observed as a result of manganese substitution. The Fourier transform infrared (FT-IR) spectra obtained with KBr pellet data reveal the structure of the oxide lattice constituted by LiO6and NiO6octahedra. The conductivity studies are characterized by (EIS) in the frequency range of 42 Hz to 1 MHz at room temperature to 120 °C. The dielectric properties are analyzed in the framework of complex dielectric permittivity and complex electric modulus formalisms. It indicates that the conductivity increases with increasing temperature. The fitting data of EIS plots replicate the non-Debye relaxation process with negative temperature coefficient of resistance (NTCR) behavior.

Synthesis, crystal structure and dielectric properties of C6H18N2SbCl5

The result of the X‐ray diffraction, differential scanning calorimetry and dielectric studies on a new crystal material C6H18N2SbCl5 is presented. The new organic–inorganic compound has been synthesized and characterized by the X‐ray diffraction method at 296(2) K. It crystallizes in the monoclinic P21/n space group. The cell dimensions are: a = 5.8617(1) Å, b = 15.7069(2) Å, c = 16.6693(2) Å, β = 97.627(1)° and Z = 4. The crystal structure consists of a discrete ionic layer of (C6H18N2)2+ cations and [SbCl5]2− anions linked via simple and bifurcated N―H · · · Cl hydrogen bonds. DSC analysis shows that this compound undergoes a phase transition at about (384 ± 2) K. AC and DC conductivities, complex dielectric permittivity ε*(ω) and complex electrical modulus M*(ω) were respectively studied as temperature and frequency functions. The combined data support each other and confirm the existence of a structural phase transition at about 384 K. Moreover, the temperature dependence of the DC conductivity and relaxation frequency followed the Arrhenius relation. The frequency dependence of the real part of the AC conductivity in both phases follows the Jonscher's universal dynamic law: . The behavior of s(T) with temperature suggests that the hopping over barrier model (CBH) and the small polaron tunneling mechanism (SPTM) prevail in phases I and II, respectively. Copyright © 2016 John Wiley & Sons, Ltd.

Frequency and voltage dependence of dielectric properties, complex electric modulus, and electrical conductivity in Au/7% graphene doped‐PVA/n‐Si (MPS) structures

ABSTRACTIn order to increase the capacitance of Au/n‐Si (MS) structure, 7% graphene doped PVA was coated on n‐Si as an interfacial layer. The measured data of capacitance (C) and conductance (G/ω) of Au/7% graphene doped‐PVA/n‐Si (MPS) structure was utilized for the calculation of real and imaginary parts of complex permittivity (ε* = ε′ − jε″), loss tangent (tanδ), complex electric modulus (M* = M′ + jM″), and electrical conductivity (σ). The admittance measurements (C and G/ω) were carried out in the frequency range of 0.5 kHz to 1 MHz at room temperature. Frequency dependence of the dielectric constant (ε′), dielectric loss (ε″) and tanδ shows a dispersive behavior at low frequencies. This behavior was explained by Maxwell–Wagner relaxation. Due to the dipolar and the interfacial polarizations, as well as the surface states (Nss) and the interfacial PVA layer, the parameters exhibited a strong dependence on frequency and applied bias voltage. The σ versus log(f) plot exhibited both low and high frequency dispersion phenomena such that at low frequencies σ value corresponding to the dc conductivity (σdc), but at high frequencies it corresponds to the ac conductivity (σac). M′ and M″, both, have low values in the low frequency region. However, an increase is observed with the increasing frequency due to the short‐range mobility of charge carriers. As a result, the change in dielectric parameters and electric modulus with frequency is the result of relaxation phenomena and surface states. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43827.

Complex impedance and electric modulus studies of Al substituted Co0.4Cu0.2Zn0.4AlxFe2-xO4 ferrites prepared by auto combustion technique

ABSTRACTAl substituted Co0.4Cu0.2Zn0.4AlxFe2-xO4 (x = 0.0, 0.1, 0.2, 0.3, 0.4 and 0.5) ferrites have been prepared using auto combustion route. X-ray diffraction studies revealed the formation of single phase spinel type cubical structure. The dielectric properties of the samples at room temperature have been studied over the frequency range of 20 Hz to 15 MHz. The dielectric constant and loss tangent is found to decrease with increasing Al content. Dielectric spectra analysis and modulus show the non-Debye type behavior in the material. Complex impedance spectra of the samples have been analyzed and explained using the Cole-Cole expression. The complex impedance data are indicative of the dominance of grain boundary resistance. AC conductivity has a trend to decrease with Al content and a shift of hopping frequency towards lower frequency is also observed.

Structural and Dielectric Properties of the New Potassium Heptachlorid/Iodid Tricadmium Tetrahydrate KCd3Cl6.89I0.11·4H2O

The crystal structure of KCd3Cl6.89I0.11·4H2O is determined by X-ray diffraction analysis. The space group is P21/m with a = 6.6903 (3) A, b = 16.1382 (7) A, c = 7.0628 (3) A, V(A3) = 762.16 (6), Z = 2 and F(000) = 5412. The residuals are R1 = 0.019 and wR2 = 0.04, for 1947 observed reflections at 293 K. The atomic arrangement of this structure may be considered as a succession of chains built up CdX6 and CdX5(H2O) octahedra (with X = Cl or I). The main feature of this structure is the coexistence of hydrogen bonds O–H…Cl/I ensuring the cohesion of the crystal. The complex impedance of the compound KCd3Cl6.89I0.11·4H2O has been investigated in the temperature range 443–532 K and in the frequency range 200 Hz–5 MHz. Dielectric data were analyzed using complex permittivity e* and complex electrical modulus M* for the sample at various temperatures. The conductivity follows the Arrhenius relation. Hopping frequency was determined and activation energy of hopping is almost equal to the activation energy of conduction. The Z′ and Z″ versus frequency plots are well fitted to an equivalent circuit model. The circuits consist of the parallel combination of bulk resistance Rp and constant phase elements CPE. Crystals of KCd3Cl6.89I0.11·4H2O undergo one endothermic peak at 368 K. This transition detected by DSC and analyzed by dielectric measurements using the impedance and modulus spectroscopy techniques.

TiO2 reinforced polymeric nanocomposites of HCl‐doped polyaniline and their properties

Polyaniline (PANI)‐titanium dioxide (TiO2) nanocomposite was synthesized via in‐situ polymerization in acidic medium using ammonium per sulfate as oxidant. The formation of nanocomposite was examined by Fourier transform‐infrared spectroscopy, X‐ray diffraction, field effect scanning electron microscopy, and energy dispersive X‐ray spectroscopy, respectively. The dielectric properties were examined using LCR meter in the frequency range 100 Hz–5 MHz and it was explained in terms of complex dielectric permittivity and electrical modulus. The optical properties were examined using UV‐VIS spectroscopy in the wavelength range 200–800 nm. The thermal properties were examined in the temperature range 30°C–800°C. The improved performance in dielectric, electrical, optical, and thermal properties enables PANI‐TiO2 nanocomposite for its use in actuators, dynamic random access memory, and semiconductor devices. POLYM. COMPOS., 38:E108–E117, 2017. © 2016 Society of Plastics Engineers

Abnormal resistivity-temperature characteristic in fluorite type Bi/K-substituted ceria ceramics

Bi/K-substituted CeO2 (BixKyCeO2+δ, x and y are 0.2 or 0.3) ceramics were prepared by a wet chemical route. The BixKyCeO2+δ ceramics have cubic fluorite crystalline structure and show an abnormal resistivity-temperature characteristic in which the resistivities increase sharply at 150−190 °C. In situ XRD investigations revealed that the Bi0.3K0.2CeO2.55 ceramic maintained the cubic fluorite structure and did not show any detectable phase transition excepting the lattice parameters increased during heating from 25 to 220 °C. The complex impedance and electrical modulus analysis were performed to reveal the abnormal resistivity-temperature effect. The electrical properties are attributed to the grain effect instead of the grain-boundary effect. The abnormal resistivity-temperature characteristic was proposed to originate from the transition of conduction models from a long-range conduction to a localized conduction.