Concentration Dependence Of Electrical Conductivity Research Articles

Sigmoidal Dependence of Electrical Conductivity of Thin PEDOT:PSS Films on Concentration of Linear Glycols as a Processing Additive.

We investigate the sigmoidal concentration dependence of electrical conductivity of poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) processed with linear glycol-based additives such as ethylene glycol (EG), diethylene glycol (DEG), triethylene glycol (TEG), hexaethylene glycol (HEG), and ethylene glycol monomethyl ether (EGME). We observe that a sharp transition of conductivity occurs at the additive concentration of ~0.6 wt.%. EG, DEG, and TEG are effective in conductivity enhancement, showing the saturation conductivities of 271.8, 325.4, and 326.2 S/cm, respectively. Optical transmittance and photoelectron spectroscopic features are rather invariant when the glycols are used as an additive. Two different figures of merit, calculated from both sheet resistance and optical transmittance to describe the performance of the transparent electrodes, indicate that both DEG and TEG are two most effective additives among the series in fabrication of transparent electrodes based on PEDOT:PSS films with a thickness of ~50–60 nm.

Temperature Dependence of Field-Effect Thermoelectric Power in Rubrene Crystals

Gate-induced carrier concentration dependence of electrical conductivity σ and thermoelectric power S of rubrene crystals is investigated down to low temperatures (T) using laser heating, and the r...

Electrically Conductive Composite based on Functionalized Carbon Nanotubes/Epoxy Resin

This work is devoted to the study of the effect of carbon nanotubes functionalization on the electrical conductivity of composite materials based on them. Carbon nanotubes were functionalized by treatment in nitric acid and isopropyl alcohol. Changes in the morphology of multi-walled carbon nanotubes during liquid-phase functionalization were investigated using Auger-electron microscopy. Samples of composite material on the basis of initial and functionalized carbon nanotubes and epoxy resin were prepared and the concentration dependence of electrical conductivity using the four-probe method was studied. The study reveals the effect of functionalization in various solutions on the electrophysical properties of the obtained carbon nanotubes/epoxy composites.

Concentration dependences of electrical conductivity and the Hall effect of the CexSn1–xSe single crystals

The concentration dependences of the Hall coefficient, electrical conductivity, and charge carrier mobility in CexSn1–xSe (х ≤ 0.02) are studied over a temperature range of 77–400 K. In the considered samples, impurities are compensated with intrinsic defects. As the cerium concentration increases (x = 0.01; 0.015), the concentration of donor impurities grows, and a change in the type of conductivity is observed.

Measurement and correlation of electrical conductivity of ionic liquid [EMIM][DCA] in propylene carbonate and γ-butyrolactone

Electrical conductivities of ionic liquid (IL) 1-ethyl-3-methylimidazolium dicyanamide ([EMIM][DCA]) in propylene carbonate (PC) and γ-butyrolactone (GBL) were measured and correlated. The effects of temperature and IL concentration on the electrical conductivity were investigated comprehensively. The electrical conductivity of mixture increases with increasing temperature. When the mole fraction of IL in mixture increases from 0 to 1, electrical conductivity increases to a maximum value, and then decreases with IL mole fraction. Besides, the maximum point moves to high IL concentration as temperature increasing. The electrical conductivity data were correlated by Vogel-Tamman-Fulcher (VTF) and Arrhenius equation. VTF equation describes the temperature dependence of electrical conductivity with high precision, but it cannot be used to describe the effects of IL concentration. Arrhenius equation is able to describe the temperature and IL concentration dependence of electrical conductivity, but the accuracy is modest. In Arrhenius equation, the relationship between parameters (activation energy Ea and pre-exponential factor A) and the mole fraction of IL were obtained. Taking advantages of both Arrhenius equation and VTF equation, we proposed an improved four-parameter equation (quasi-Arrhenius equation) to correlate the electrical conductivity, in which the dependence of temperature and IL concentration were included, and the correlation results agreed well with experimental data.

Кристаллическая структура и проводимость висмут-содержащих сложных оксидов

In the paper, a comprehensive systematic study of different classes of bismuth containing oxide compounds was carried out. The relationship between composition, temperature and concentration regions of existence of stable, specific structure and properties of solid solutions on the basis of vanadates, molybdates, niobates and bismuth was found. The general regularities of synthesis of solid solutions with different variants of solid-phase and soluble methods were determined. On this basis, the optimal conditions for obtaining single-phase materials were formulated. For the first time the temperature and concentration boundaries of the regions of homogeneity and areas of stable existence of polymorphic modifications of solid solutions were defined and/or refined. The structural parameters of the synthesized phases were determined. By the method of electrochemical impedance spectroscopy the nature and features of impedance spectra, the temperature and concentration dependences of electrical conductivity of ceramic materials based on bismuth containing complex oxides were identified.

Electronic and thermoelectric properties of InN studied using ab initio density functional theory and Boltzmann transport calculations

The thermoelectric properties of indium nitride in the most stable wurtzite phase (w-InN) as a function of electron and hole concentrations and temperature were studied by solving the semiclassical Boltzmann transport equations in conjunction with ab initio electronic structure calculations, within Density Functional Theory. Based on maximally localized Wannier function basis set and the ab initio band energies, results for the Seebeck coefficient are presented and compared with available experimental data for n-type as well as p-type systems. Also, theoretical results for electric conductivity and power factor are presented. Most cases showed good agreement between the calculated properties and experimental data for w-InN unintentionally and p-type doped with magnesium. Our predictions for temperature and concentration dependences of electrical conductivity and power factor revealed a promising use of InN for intermediate and high temperature thermoelectric applications. The rigid band approach and constant scattering time approximation were utilized in the calculations.

Ionic Conduction in Electrolyte Solution

The electrical conductivity in aqueous solutions of electrolytes has been obtained in terms of inter-particle potentials and pair distribution functions, based on a generalized Langevin equation for the cation and anion. This treatment allows us to connect and compare with the work of a computer simulation where the inter-particle potentials are the only input. The results for the concentration dependence of electrical conductivity are basically represented as a function of the square root of concentration. The electrophoretic and relaxation effects are discussed from a microscopic view point. The ionic hydration in electrolytic solution is also discussed. Available inter-particle potentials in aqueous solutions of electrolytes are proposed. The numerical application is carried out for sodium chloride and other aqueous electrolyte solutions.

Volumetric, viscosity, and electrical conductivity properties of aqueous solutions of two n-butylammonium-based protic ionic liquids at several temperatures

Densities and viscosities of (n-butylammonium acetate (N4AC) protic ionic liquid+water) and (n-butylammonium nitrate (N4NO3) protic ionic liquid+water) mixtures were measured at T=(293.15, 298.15, 303.15, 308.15, and 313.15) K under atmospheric pressure. Electrical conductivities of the above-mentioned systems were determined at 298.15K. Excess molar volumes and viscosity deviations were obtained from the experimental results and fitted to the Redlich–Kister equation with satisfactory results. Other volumetric properties, such as apparent molar volumes, partial molar volumes, and excess partial molar volumes were also calculated. The concentration dependence of electrical conductivity was fitted according to the empirical Casteel–Amis equation. Based on the measured and derived properties, the molecular interactions and structural factors in the above-mentioned systems were discussed.

Electrochemical characteristics of propylene carbonate solutions of tetraethylammonium tetrafluoroborate

The specific and molar electric conductivities of propylene carbonate solutions of Et4NBF4 with concentrations of 0.15–1.4 m were determined at 283.15, 298.15, and 313.15 K. The temperature dependence of the electric conductivity of the system was analyzed. The concentration dependence of electric conductivity was described in terms of the Castell-Amis equation. A comparative analysis of the charge transfer in Et4NBF4 and LiAsF6 systems in propylene carbonate was performed using the concept of quasicrystallinity of concentrated electrolyte solutions. The range of potentials in which the electrolyte solutions are stable on a platinum electrode was determined.

Electrical conductivity of systems based on Na3AlF6-SiO2 melt

AbstractThe electrical conductivity of molten binary and ternary mixtures based on the NaF-AlF3-SiO2 system was investigated by means of a tube-cell (composed of pyrolytic boron nitride) with stationary electrodes. An impedance/gain-phase analyser (National Instruments; a high-performance modular chassis controlled by Labview™ software) was used for the cell impedance measurement. The conductivity was found to vary linearly with temperature in all the mixtures investigated. The concentration dependence of electrical conductivity (isotherms) thus obtained was divided into two parts. The first represents the concentration region of up to 10 mole % of SiO2, the second the region with a higher concentration of SiO2 (from 10 mole % to 40 mole %). While the conductivity decreased considerably with the concentration of SiO2 in the second part, it increased surprisingly in the low concentration range. From these results, the influence of electrolyte composition and temperature on the electrical conductivity was examined.

Thermodynamic properties of aqueous solutions of two ammonium-based protic ionic liquids at 298.15 K

Densities (ρ), refractive indices (nD) and electrical conductivities (κ) of ethylammonium acetate (N2Ac) protic ionic liquid+water and propylammonium acetate (N3Ac) protic ionic liquid+water binary mixtures over the entire composition range were measured at 298.15K under atmospheric pressure. The excess molar volumes (VE), apparent molar volumes (Vϕi), partial molar volumes (V¯m,i) and excess partial molar volumes (V¯m,iE) of the binary mixtures were calculated from the density data. The refractive index deviations (ΔnD) of the binary mixtures were determined using the refractive index data. The excess molar volumes and refractive index deviations were correlated with the Redlich–Kister equation. The excess molar volumes of the above-mentioned systems are negative over the whole composition range, while the refractive index deviations are positive. The concentration dependence of electrical conductivity was fitted according to the empirical Casteel–Amis equation. The intermolecular interactions and structural effects were analyzed on the basis of the measured and the derived properties.

The effect of aprotic solvent on the selectivity of ion-exchange membranes

The effect of N,N-dimethylacetamide on the selectivity of heterogeneous (MK-40, MA-40, and MA-41) and homogeneous (MF-4SK) ion-exchange membranes is studied for the first time. Concentration dependences of electrical conductivity and diffusion permeability of the membranes were measured experimentally over wide lithium chloride concentrations; on their basis, electrodiffusion coefficients of the co- and counterions were calculated. The interrelation between the electrodiffusion coefficients and the specific moisture capacity of the heterogeneous and homogeneous membranes (which affect their selectivity) is revealed. The calculated electrodiffusion coefficients were used in the calculations of the electromigration transport numbers of counterions in the initial membranes and those processed in mixed solvent. It is shown that the heterogeneous membrane selectivity either increased under the action of the aprotic solvent to polymer material (MA-40, MA-41) or remained practically unchanged (MK-40); the selectivity of homogeneous perfluorinated membranes (e.g., MF-4SK) decreased, thus approaching that of the studied heterogeneous anion-exchange membranes.

Thermodynamics of micellization of imidazolium ionic liquids in aqueous solutions

The structural similarity between some ionic liquids (ILs) and ionic surfactants, indicates that ILs are expected to exhibit surface adsorption and aggregation properties. The Krafft temperature and the temperature dependence of the critical micelle concentration (CMC) were determined for four imidazolium ionic liquids with varying chain length by measuring concentration dependence of electrical conductivity at different temperatures. The magnitude of the thermodynamic parameters of the micelle formation provide valuable information about the driving force of micellization of these compounds, therefore, the parameters of these chemicals were estimated from the degree of ionization, and the CMC. The thermodynamic parameters were correlated to directly measured values using isothermal titration calorimetry (ITC). It was found that the long-chained imidazolium ILs show similar thermodynamic characteristics as traditional cationic surfactants, whereas the Krafft temperature was shown to be lower than that of traditional cationic surfactants of similar chain length.

Electrical conductivity of cation-and anion-exchange membranes in ampholyte solutions

Several laws governing ampholyte transport through ion-exchange membranes are established by a comparative analysis of the concentration dependence of electrical conductivity for homogeneous (CMX, AMX) and heterogeneous (MK-40, MA-41) membranes in NaCl, LysHCl, and NaH2PO4 solutions. The increase in the electrical conductivity of membranes in ampholyte solutions as the solutions become more dilute is explained by the increased fraction of divalent ions of the amino acid (cation-exchange membrane) or from phosphoric acid (anion-exchange membrane) in the membrane as a result of Donnan exclusion of hydrolysis products (hydroxide ions or protons, respectively).

Self-aggregation of ionic liquids in aqueous media: A thermodynamic study

Aggregation process of the ionic liquids (ILs), 1-butyl-3-methylimidazolium tetrafluoroborate [C4mim][BF4], 3-methyl-1-octylimidazolium tetrafluoroborate [C8mim][BF4], 3-methyl-1-octylimidazolium chloride [C8mim][Cl], and N-butyl-3-methylpyridinium chloride [C4mpy][Cl], in the aqueous solutions has been characterized by electrical conductivity, density, and speed of sound measurements at 298.15 K. The critical aggregation concentration (CAC), the standard Gibbs energy of aggregation ΔGagg.∘, isentropic compressibility κs and changes in the isentropic compressibility upon aggregation Δκs,agg for the ionic liquids were derived from the experimental data. The dependence of the CAC, ΔGagg.∘, and Δκs,agg on the nature of the cations and anions has been examined. The aggregation number n for various ILs was determined by applying the mass action theory to the concentration dependence of electrical conductivity and compressibility. Aggregation properties showed fairly good agreement with our previously reported results of 1H NMR and fluorescence spectroscopy.

Concentration dependence of electric conductivity for fluorine-containing sodium borate glasses

The influence of sodium fluoride additives on the physicochemical properties of glasses in the Na2O-B2O3 systems is investigated. The introduction of sodium fluoride into the Na2O · 2B2O3 and Na2O · 3B2O3 glasses leads to an increase in the electric conductivity. The temperature-concentration dependence of the electric conductivity has been investigated. It is shown that, in glasses of the NaF-Na2O · 2B2O3 system, an increase in the volume concentration of sodium ions from 2.4 × 10−2 to ∼3 × 10−2 mol/cm3 is accompanied by an insignificant decrease in the activation energy Eσ from 1.44 to 1.38 eV and a sharp (by a factor of ∼30) increase in the electric conductivity. In glasses of the NaF-Na2O · 3B2O3 system, an increase in the concentration of sodium ions from 1.8 × 10−2 to ∼2.3 × 10−2 mol/cm3 brings about an increase in the electric conductivity by a factor of approximately 100 and an increase in Eσ from 1.6 to 1.83 eV. A further increase in the concentration of sodium ions (up to 2.5 × 10−2 mol/cm3) virtually does not affect the electric conductivity and Eσ. At the same concentration of sodium ions (∼2.46 × 10−2 mol/cm3) in the 9.8NaF · 90.2[Na2O · 2B2O3] and 57.1NaF · 42.9[Na2O · 3B2O3] glasses, the electric conductivity and the activation energy are considerably higher in the glass with a larger fluorine content. The regularities revealed are interpreted in the framework of the microinhomogeneous glass structure.

POLARIZED EXAFS AND NEAR-EDGE SPECTRA OF HALOGEN-DOPED POLYACETYLENE

Polarized EXAFS and near-edge spectra were measured for (CHBry)x and (CHIy)x on the Br K- and I L-edges over a wide range of dopant concentration. The analysis of EXAFS and near-edge spectra indicates that, in the lightly doped region (0.01 0.2). Bromines are incorporated as isolated ions in the early stage of doping (y < 0.01). In (CHIy)x, iodines form linear polyions which are chemically less reactive. The difference in the magnitude and dopant concentration dependence of electrical conductivity between bromine and iodine doping is ascribed to the degree of termination of conjugated chains by an addition reaction of halogens.

Cluster-components model interpretation of the concentration dependence of electrical conductivity in doped ionic crystals containing Frenkel defects

The cluster-components method is used to study defect behavior and to describe the “property — composition” dependence in binary ionic compounds. A qualitative estimate of the concentration dependence of defects is given, together with the “electrical conductivity — composition” dependence based on the defects. It is shown that when linear approximation for the concentration dependences on a single type of defect are coupled with the experimental data, one can describe the concentration dependence of the electrical conductivity. The calculated results are in good agreement with experiment. The dependence on vacancy and interstitial concentration can be used to calculate other properties.