Conductivity Plots Research Articles

Temperature-induced phase separation in pseudoternary mixtures of Triton X-100–butanol–kerosene–water

ABSTRACTThe transparent Winsor IV domain in the phase diagram of the mixtures of emulsifier (Triton X-100 and butanol), oil (kerosene), and water is found to be 34% of the total phase diagram in presence of emulsifier with surfactant:cosurfactant::1:1, and is water dominant. Increase in cosurfactant/surfactant ratio inverts the Winsor IV domain to become oil rich. The plot of conductance of the microemulsions prepared by substituting water by brine against water content depicts the existence of three distinct phases like oil-in-water, bicontinuous, and water-in-oil microemulsion in the phase diagram. The phase contrast micrographs of the mixtures of different compositions in these three different phases reveal the existence of microdroplets of oil dispersed in water and water dispersed in oil. Further, the dynamic light scattering studies of these solutions reveal an inhomogeneity in the size distribution of the droplets. A temperature-induced clouding in the microemulsion domain leading to phase separation has been observed. Additives like glucose, sucrose, and sodium chloride decrease the cloud point (CP), while addition of ammonium thiocyanate increases it. A quantitative relationship of the clouding temperature with the composition of the microemulsion has been established. With increase in oil and emulsifier, the cloud point of the microemulsion increases. The separated phases after the clouding have been used for preconcentration of water-soluble metal ions as well as oil-soluble dyes. The turbid systems on heating led to separation into three isotropic phases which are found to be stable at ambient temperature. The stability of these phases is ascribed to the formation of stable microemulsions by mass transfer from one phase to other.

Relaxation and conduction mechanism of Dy3+ substituted SrBi2Ta2O9 ceramics

Dysprosium substituted SrBi2Ta2O9 Aurivillius ceramics with general formula Sr1−xDy2x/3Bi2Ta2O9 (x = 0.0, 0.025, 0.05, 0.075, 0.1) are prepared by using the solid state reaction method. X-ray diffraction pattern revealed a single phase orthorhombic (A21am) structure up to x ≤ 0.05 and deleterious phase is obtained for higher concentration. Scanning electron microscope figures show well defined anisotropic grains in all compositions. The electrical relaxation mechanism is studied by the impedance spectroscopy analysis. The Cole–Cole plots are fitted with equivalent circuit and the fitting parameters are presented. The Kohlrausch–Williams–Watts (KWW) function is used to explain the modulus analysis and confirms the coexistence of grain and grain boundary effect. The dispersion of conductivity with frequency is well explained using Jonscher's power law and DC conductivity values are obtained from the fittings. Activation energies are determined from the Arrhenius fitting of impedance and conductivity plots. The determined activation energies give an idea about the reduction of a cluster of vacancies due to the neutralization of oppositely charge vacancies which requires lower energy to mobilize the charge carrier than the individuals.

Effect of reduction/oxidation annealing on the dielectric relaxation and electrical properties of Aurivillius Na0.5Gd0.5Bi4Ti4O15 ceramics

(a) Arrhenius plots of ac conductivity of argon and oxygen annealed and as-sintered samples at 100 Hz. (b) Variation of relaxation frequency vs. temperature of NGBT ceramics.

Quaternary Polyethylene Oxide Electrolytes Containing Ionic Liquid for Lithium Polymer Battery

Herein we report a comparative study of quaternary polymer electrolyte membranes, comprising polyethylene oxide (PEO), lithium bis(trifluoromethanesulfonyl)imide, LiTFSI(salt), SiO2-filler and N-methyl-N-butyl-pyrrolidinium bis(trifluoromethanesulfonyl)imide (Pyr1,4TFSI) ionic liquid. The membranes are developed in view of an efficient application in polymeric lithium battery. The study shows improvement of the ionic conductivity and the stability of the lithium interphase by increasing the Pyr1,4TFSI content up to 20% wt, as revealed by Arrhenius conductivity plots, electrochemical impedance spectroscopy as well as by cyclic test in symmetrical lithium cell. This trend is directly reflected in enhanced behavior of lithium polymer cell using LiFePO4, in terms of delivered capacity. Furthermore, the measurement indicated that setting up a proper amount of added IL is a key requirement for an optimal behavior of the electrolyte in battery.

Electrochemical Impedance Spectroscopy and Characterization of 20% Yttria doped Cerium on Silicon

Bare silicon and 20% yttria stabilized ceria on a silicon substrate are annealed. The annealed substrates are analyzed at varying temperatures using electrochemical impedance spectroscopy. The impedance data is fitted against appropriate equivalent circuits and the fitted data is characterized with an Arrhenius plot and a plot of the ionic conductivity against temperature. The 20% YDC sample is found to have a high ionic conductivity, and therefore should be studied further in order to determine the practicality of using YDC as an electrolyte.

A Comparative Study on the Aggregation and Thermodynamic Properties of Anionic Sodium Dodecylsulphate and Cationic Cetyltrimethylammonium Bromide in Aqueous Medium: Effect of the Co‐solvent N‐Methylacetamide

AbstractThe effect of co‐solvent N‐methylacetamide (NMA) (0.035, 0.046, 0.127, and 0.258 mol kg−1) on the micellization behaviour of anionic surfactant sodium dodecylsulphate (SDS) (3.21–10.35 mmol kg−1) and cationic surfactant cetyltrimethylammonium bromide (CTAB) (0.19–3.72 mmol kg−1) in aqueous solution was explored by employing conductivity measurements at different temperatures (298.15–313.15 K). The critical micelle concentration (CMC) values for SDS and CTAB in aqueous solutions of NMA were determined from the conductivity versus surfactant concentration plots. The variations in the CMC values of SDS with NMA concentration are in striking contrast to those observed in the case of CTAB. The various relevant thermodynamic parameters of micellization, viz. standard enthalpy change, ΔHmo, standard entropy change, ΔSmo, and standard Gibbs free energy change, ΔGmo, were determined using the temperature variation of the CMC values and counterion binding. The results not only relate these thermodynamic parameters to the consequences of intermolecular interactions but are also able to differentiate between SDS–water–NMA and CTAB–water–NMA systems in terms of contributions from head groups as well as alkyl chains of surfactants.

Maxwell-Wanger/Debye Effects and Complex Impedance Studies on Bi4Ti3O12-0.04Fe2O3 Ceramics

Dense ceramics in the solid solution system, Bi4Ti3O12-0.04Fe2O3 (BIT-0.04Fe) ceramics were prepared by conventional solid-state method. And the electrical properties were investigated by the dielectric and impedance spectroscopies. Moreover, the BIT-0.04Fe ceramic exhibit only one loss peak which can be analyzed in terms of the Maxwell-Wagner capacitor model at lower temperature, while the second peak related to the space charge polarization between the ceramic and electrode appeared above 920K. The Arrhenius plot of the total conductivity of BIT-0.04Fe ceramic indicates three different activation energies. The impedance complex plane plots of BIT-0.04Fe ceramic turned into one semicircular arc at 353 K and then to one semicircular arc and a line at 433 K and two single semicircular arcs at 513 K, which were analyzed as three different equivalent circuits.

EFFECT OF MnO2 FILLER ON THE ELECTRICAL AND DIELECTRIC PROPERTIES OF BINARY Li2CO3/LiI ELECTROLYTE

Inorganic electrolyte consisting of Li2CO3 and LiI with the incorporation of MnO2 as fillers was prepared by a mechanical milling technique. The effects of ceramic filler concentration on the electrolyte host system were investigated by deploying electrical impedance spectroscopy, EIS measurement at a temperature range of 298-373K. It was revealed that incorporating 9 wt. % MnO2 filler in Li2CO3/LiI electrolyte significantly enhanced the electrical conductivity from 4x10-3 S/cm up to 8x10-3 S/cm. Nano-particle inorganic oxides have been found to act as ions dissociation enhancer in solid electrolytes. Dielectric analysis was performed to investigate the ions migration process in solid electrolyte. The dielectric study showed that the ionic conductivity of the electrolyte was observed to increase as a function of temperature, suggesting that the system is thermally assisted. The plots of electrical conductivity, as a function of temperature have been varied from 298 – 373K and were found to obey the Arrhenius law.

Dielectric and Electrical Properties of BiFeO3-PbZrO3 Composites

The dielectric and electrical properties of composites prepared by addition of two different amounts of PbZrO3 (PZO) to BiFeO3 (BFO) are discussed. The composites (1 − x)(BiFeO3)-x(PbZrO3) (x = 0.5, 0.7; i.e., 0.5BF-0.5PZ and 0.3BF-0.7PZ) were synthesized by solid-state reaction. X-ray diffraction analysis confirmed formation of composites with a rhombohedral structure at room temperature. Scanning electron microscopy revealed homogeneously distributed grains. Dielectric constants and dielectric loss increased with decreasing PZO content whereas the transition temperature shifted to higher temperature with decreasing PZO content. Hysteresis loops confirmed the ferroelectric nature of the materials. The Nyquist plot was indicative of the contribution of the bulk effect and a small contribution from the grain boundary effect. Temperature-dependent relaxation occurred for both materials. Non-Debye type electrical impedance was confirmed by asymmetric peak broadening and a spread of relaxation times. Activation energies were calculated from plots of ac conductivity as a function of temperature by linear fitting. Dc and ac conductivity increased with increasing temperature. Activation energies calculated from the complex impedance plot and from the fitted Jonscher power law were very similar, implying conduction by a similar type of charge carrier in both composites.

Electrical conduction mechanism in Se90-xTe5Sn5Inx (x = 0, 3, 6 and 9) multi-component glassy alloys

Electrical conductivity of Se90-xTe5Sn5Inx (x = 0, 3, 6 and 9) glassy systems was studied employing impedance spectroscopic technique in the frequency range 100 Hz to 1 MHz and in the temperature range 308-388 K. The DC conductivity (σdc) at each temperature was evaluated from the low frequency plateau region for all the samples under investigation. The bulk conductivity for each sample was also evaluated from Nyquist impedance plots. The semicircle shape of Nyquist plot exhibit dipolar nature of samples. The activation energy for glassy, amorphous and crystalline region from the Arrhenius plot of the DC conductivity and bulk conductivity was evaluated. From the results it is found that activation energy varied from 0.091 to 0.194 eV in glassy, 0.686 to 0.002 eV in amorphous and 0.215 to 0.503 eV in crystalline region. The activation energy (ΔE) from DC conductivity and bulk conductivity found to be close in corresponding regions. The pre-exponential factor was also calculated for all three regions.

Interaction between Zn2+ cations and n-methyl-2-pyrrolidone in ionic liquid-based Gel Polymer Electrolytes for Zn batteries

Gel Polymer Electrolytes (GPEs) composed by 1-Ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide (EMIM TFSI), ZnTf2 salt, and poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP) are synthesized using n-methyl-2-pyrrolidone (NMP) as solvent. Structural and Thermal characterization of GPEs with different ZnTf2 concentrations are analyzed by ATR-FTIR, XRD, DSC and TG. Ionic conductivity versus temperature plots obeys the Vogel-Tammen-Fulcher (VTF) behavior and activation energy values are deduced from the slopes. Use of NMP solvent turns out to be a key factor for improving the Zn2+ transport inside the GPE due to the interaction between Zn2+ cations and carbonyl groups of the NMP. High values of ionic conductivity and low activation energy values, together with the high reversibility and high current density obtained in the voltammograms reveal these GPEs as good candidates to be used in Zn batteries. Furthermore, ionic liquids-based GPEs are probed in Zn/MnO2 batteries, resulting specific capacities of 125mAhg−1.

The effects of Bi4Ti3O12 interfacial ferroelectric layer on the dielectric properties of Au/n-Si structures

Au/n-Si metal-semiconductor (MS) and Au/Bi4Ti3O12/n-Si metal-ferroelectric-semiconductor (MFS) structures were fabricated and admittance measurements were held between 5 kHz and 1 MHz at room temperature so that dielectric properties of these structures could be investigated. The ferroelectric interfacial layer Bi4Ti3O12 decreased the polarization voltage by providing permanent dipoles at metal/semiconductor interface. Depending on different mechanisms, dispersion behavior was observed in dielectric constant, dielectric loss and loss tangent versus bias voltage plots of both MS and MFS structures. The real and imaginary parts of complex modulus of MFS structure take smaller values than those of MS structure, because permanent dipoles in ferroelectric layer cause a large spontaneous polarization mechanism. While the dispersion in AC conductivity versus frequency plots of MS structure was observed at high frequencies, for MFS structure it was observed at lower frequencies.

Thermal conductivity of disordered AA-stacked bilayer graphene in the presence of bias voltage

We study thermal conductivity of biased bilayer graphene doped with acceptor impurity atoms for AA-stacking in the context of tight binding model Hamiltonian. The effect of scattering by dilute charged impurities is discussed in terms of the self-consistent Born approximation. Green’s function approach has been implemented to find the behavior of thermal conductivity of carbon nanotubes within linear response theory. We have found the temperature dependence of thermal conductivity for different values of concentration and scattering strength of dopant impurity. Also the dependence of thermal conductivity on the chemical potential and bias voltage has been investigated in details. A peak appears in the plot of thermal conductivity versus chemical potential. Furthermore we find thermal transport rises with temperature for any impurity concentration and scattering strength.

Dielectric relaxation behaviour of ethylene-vinyl acetate–exfoliated graphene nanoplatelets (xGnP) composites

The dielectric relaxation behaviour of the composites prepared by solution casting of exfoliated graphene nanoplatelets (xGnP) and ethylene vinyl acetate (EVA) were investigated. The percolation threshold was achieved at 17 phr (parts per hundred rubber) of xGnP loading. Filler contributions to the electrical property were observed by the increase in ac conductivity and permittivity in the composites. The effect of filler loading on the complex and real parts of the impedance were investigated. The effect of temperature on dielectric loss tangent, ac conductivity and Nyquist plot of xGnP reinforced EVA also been studied. A careful comparison of the experimental complex impedance plots and model fitted plots were studied which satisfied the accuracy of the data obtained experimentally.

Effect of Ionic Conductivity on Response Speed of SrTiO3-Based All-Solid-State Electric-Double-Layer Transistor.

An all-solid-state electric-double-layer transistor (EDLT) with a Y-stabilized ZrO₂ (YSZ) proton conductor/SrTiO₃ (STO) single crystal has been fabricated to investigate ionic conductivity effect on the response speed, which should be a key parameter for development of next-generation EDLTs. The drain current exhibited a 4-order-of-magnitude increment by electrostatic carrier doping at the YSZ/STO interface due to ion migration, and the behavior strongly depended on the operation temperature. An Arrhenius-type plot of the ionic conductivity (σ(i)) in the YSZ and t(c)⁻¹, which is a current-rise time needed for charge accumulation at the YSZ/STO interface, shows a synchronized variation, indicating a proportional relationship between the two parameters. Analysis of the σ(i)-t(c) diagram shows that, in contrast to conventional EDLTs, the response speed should reach picosecond order at room temperature by using extreme miniaturization and superionic conductors. Furthermore, the diagram indicates that plenty of solid electrolytes, which have not been used due to the lack of criteria for evaluation, can be a candidate for all-solid-state EDLTs exceeding the carrier density of conventional EDLTs, even though the response speed becomes comparably lower than those of FETs.

Estimation of Ion Diffusion Coefficients at the Stagnant Layer Using TiO2 Aqueous Suspension Zeta Potential Data

The solid-liquid interface of anatase-water nanofluids has been characterized. Combined data of electrophoretic mobility and conductivity of the colloidal suspensions have been used to evaluate zeta-potentials. Plots of the suspension conductivity as a function of the bulk conductivity are essentially linear, allowing for the establishment of the entire surface conductivity. The main contribution to the surface conductivity stemmed from the counter charge behind the slip plane. Whereas the diffuse layer surface conductivity is generic, the stagnant layer conductivity is system-specific; therefore, evaluation of the later requires insight into such properties as the distribution of charges and lateral mobilities. Based on a simple analytical theory we can also estimate the diffusion coefficient of counterions in the stagnant layer. The results lead to a good agreement between theory and experiment.

Dielectric response of conducting carbon-black-filled ethylene-octene copolymer microcellular foams

Dielectric response of conducting carbon-black-filled ethylene–octene copolymer microcellular foams has been investigated with variation of blowing agent and filler loading in the frequency range of 100 Hz to 5 MHz and temperature range from 30 to 100°C. With increase in blowing agent loading, the dielectric permittivity increases for both unfilled as well as carbon-black-filled microcellular foams. The experimental complex impedance plots were compared with model-fitted plots obtained by taking an equivalent circuit of (CQR) (CR).The values of Rb (bulk resistance), Rgb (grain boundary resistance), bulk capacitance (Cb), and grain boundary capacitance (Cgb) at different temperatures were calculated and compared with experimental values. The relaxation time due to bulk effect (τb) has been calculated from relaxation frequency (fr). The dc conductivity (σdc) decreases with rise in temperature indicating the existence of positive temperature coefficient of resistance in the material. The activation energy (Ea) calculated from the relaxation time due to bulk effect (τb) was found to be 0.446 eV, whereas it was 0.363 eV from the dc conductivity plot in the temperature range of 30–100°C. POLYM. COMPOS., 2015. © 2015 Society of Plastics Engineers

Polymeric Ionic Liquid Electrolytes: Effect of Inorganic Fillers

To render a battery fully solid-state, all the battery components, including the electrolyte have to be solid-state. Solid polymer electrolytes (SPE) emerged as a plausible replacements of liquid electrolytes over the past few years [1]. For these electrolytes however, low operation temperatures reduces the ionic conductivities leading to many obstacles for SPE’s utility in batteries, especially lithium ion batteries [2]. Inorganic filler materials have been shown to improve the ionic conductivity of liquid electrolytes and the mechanical properties of the solid electrolyte [2,3]. Polymeric ionic liquid (PIL) electrolytes have emerged as electrolytes that benefit from both the liquids’ high ionic conductivities and the solids’ high mechanical properties. These electrolytes have been most commonly prepared using ionic liquids blended with a polymer and a lithium salt [4]. In this study, the effect of the addition of various inorganic fillers was investigated. The investigated PIL included the polymer poly(diallyldimethylammonium) and imidazolium-based ionic liquids with various lithium salt concentrations. The synthesized PIL without the filler were shown to be free-standing and mechanically stable. The addition of inorganic filler materials such as SiO2, TiO2, or Al2O3 afforded high ionic liquid loading percentages. Figure 1 shows a photograph of the prepared films of ½ inch in diameter and 50-150 microns in thickness. The films were free-standing and provided adequate ionic conductivity performance as shown in subsequent studies. Figure 1b shows the effect of 5 wt% loading of SiO2 fillers. Various electrochemical studies were conducted to the synthesized PIL to characterize the electrochemical properties and their potential use in lithium ion batteries. Ionic conductivity measurement of the PIL at various temperatures was evaluated using electrochemical impedance spectroscopy. Two-fold improvement was observed by the addition of inorganic fillers consistently at various temperatures ranging from -10oC to 50oC. At room temperature the conductivity was measured as 1.09 mS/cm compared to 2.07 mS/cm with the addition of SiO2 fillers. The temperature and ionic conductivity relationship was fit to an Arrhenius type plot and comparison of ionic conductivity, showing an improved performance due to an improved ion-conduction pathway provided by the addition of the SiO2. Electrochemical stability window (ESW) of the synthesized PILs were measured by performing linear sweep voltammetery (LSV) at room temperature in a Li/PIL/SS cell where lithium worked as both reference and counter electrode and stainless steel as working electrode. No change in stability window value was observed after addition of filler materials. In both cases the stability window was at least 5.2 V. Lithium ion transference numbers were measured using a polarization study in Li/PIL/Li cell. Impedance spectroscopy was performed before and after polarization and polarization steady state [5]. A consistent increase of 10-15% of Li+transference number was observed with the addition of filler materials. This observation further supports the effect of the fillers on the ion-conduction pathways. [1] Xu, Kang. Chemical reviews (2014). [2] Costa, Carlos M., Maria M. Silva, and S. Lanceros-Mendez. RSC Advances 3.29 (2013): 11404-11417. [3] Bhattacharyya, Aninda J., and Joachim Maier. Advanced Materials 16.9‐10 (2004): 811-814. [4] Ye, Yun-Sheng, John Rick, and Bing-Joe Hwang. Journal of Materials Chemistry A 1.8 (2013): 2719-2743. [5] Evans, James, Colin A. Vincent, and Peter G. Bruce. Polymer 28.13 (1987): 2324-2328. Figure 1

Effect of salt and urea on complexation behavior of pharmaceutical excipient gelatin with phenothiazine drug promazine hydrochloride

An evaluation of the interactions of cationic phenothiazine drug promazine hydrochloride (PMZ) with gelatin in aqueous solution as well as in the presence of 50mM NaCl and 100mM urea, investigated through different physicochemical measurements is presented in the present study using conductometric method. PMZ is used for the control of mania and schizophrenia. The drug interacts with gelatin similar to the interaction of surfactants and polymers. The plots of specific conductivity versus concentration of the drug were nonlinear with three different linear regions with two clear breaks. The first break point, i.e., critical aggregation concentration (cac), appeared well below the typical critical micelle concentration (cmc). The second break point is considered as polymer saturation point (psp) that is akin to cmc. The cac value decreases on increasing the gelatin concentration, whereas the psp value increases for all fixed concentrations (%w/v) of gelatin which is a clear signal of the interaction of the drug with gelatin. As inorganic salts increase the ionic strength, the solubility of amphiphile (drug) is lowered by ionic screening effects, ensuing in a greater tendency to aggregates at lower concentration. As a result, both the cac and psp/cmc values decrease. By the addition of urea an increase in the surface charge of the micelles was observed followed by halt of the aggregation of the drug hence both the cac and psp/cmc values increase. Free energies of aggregation (ΔGagg), micellization (ΔGmic), polymer saturation (∆Gpsp) and transfer (ΔGt) were also evaluated.

Structural and dielectric properties of Sr3(MgTa2)O9 and Sr3(ZnTa2)O9

Herein, we report the crystal structures and morphological properties of Sr3(MgTa2)O9 (SMT) and Sr3(ZnTa2)O9 (SZT) synthesized by solid state ceramic method along with the results of alternating current impedance spectroscopic (ACIS) study in a frequency range from 50Hz to 1MHz at selective temperatures between 393 and 573K. The crystal structures of SMT and SZT have been determined by Rietveld refinement of powder X-ray diffraction pattern using an initial structural model developed on the basis of literature survey. The results indicate that both the samples possess hexagonal structure of trigonal P3¯m1 space group. The lattice parameters of SMT are a=b=5.65162Å, c=6.94440Å, α=β=90° and γ=120° and those of SZT are a=b=5.65832Å, c=6.95911Å and α=β=90° and γ=120°. SMT and SZT are isostructural and they exhibit 2:1 B site ordering with the staking sequence of {–Ta–Ta–Mg (Zn)–} (Mg for SMT and Zn for SZT) layer repeat on (111) plane of the pseudocells. The characteristic vibrational bands due to Ta–O, Mg–O and Zn–O bonds have been observed in the FTIR spectra of the samples. The FESEM micrographs of the samples show that the grains size ranges between 0.40 and 3.65μm and 0.9 to 4.2μm for SMT and SZT, respectively. To account for the polydispersive nature of the dielectric relaxation mechanism along with the effects of dc conductivity and localized space charges the variation of real (ε′) and imaginary (ε″) parts of dielectric constant with frequency has been analytically interpreted in the framework of modified Cole–Cole model. SMT and SZT having the activation energies of 0.35eV and 0.33eV, respectively (obtained from the Arrhenius plot of dc conductivity), are semiconducting in nature. The electrical current conduction in the samples occurs by polaron hopping process. Further, we have shown that chemical property of A site cations has significant role in determining the dielectric properties of A3B′B″2O9 type perovskites and these properties do not change appreciably upon replacement of the divalent B′ cations. Moreover, owing to their high dielectric constant and low dielectric loss SMT and SZT appear to be potent candidates for technological applications in radio-frequency devices.