Static Electrical Conductivity Research Articles

Revealing the Impact of Ga and Y Doping on Thermal and Electrical Behavior of LaMnO3 Ceramic Materials

The synthesis, thermal behavior and electrical properties of a series of undoped and 1% Ga- or Y-doped lanthanum manganite compounds, obtained via the sol–gel technique, are reported. Scanning electron microscopy (SEM/EDX), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR) analyses were performed on all synthesized samples. The XRD results confirmed a good crystallinity for all studied samples, and a change in the crystal structure of Ga- or Y-doped lanthanum manganite (Pm-3m space group) was observed compared to the pristine sample (R-3c space group). Thermal analysis highlighted a different behavior of the doped samples compared to the undoped sample, observed by the different mass losses in the analyzed temperature range. For these materials, it is shown for the first time that the static electrical conductivity, σDC, of Ga- or Y-doped LaMnO3 compounds increases compared to the σDC of the pristine sample, and the thermal activation energy of the process of electrical conduction, EA,cond, increases linearly with the temperature for all three studied samples.

Optical sensitivity of mono and hybrid nanomaterials dispersed PEG-based semiconducting nanofluids with high viscosity and dielectric permittivity

ABSTRACT Semiconducting nanofluids (SNFs), based on poly(ethylene glycol) (PEG200) fluid with the dispersion of 0.01 wt% mono (ZnO, TiO2, and OMMT) and 0.01+ 0.01 wt% hybrid (ZnO+OMMT, ZnO+TiO2, and TiO2+OMMT) nanomaterials, are prepared through mixing and then ultrasonic cavitation homogenised process. Ultraviolet-visible (UV-Vis) absorbance spectra of these SNFs are recorded in the 200–800 nm range and analysed for their photosensitivity and UV shielding performance and also for nanomaterials tunable dual band gaps ranging from 3 to 5 eV. The rheological investigations on these samples, at 303.15 K, validate Newtonian nanofluids of high dynamic viscosity (η ≈ 32 mP.s). Static dielectric permittivity (εs ≈ 22) and electrical conductivity (σdc ≈ 8 μS/cm) of these SNFs at 303.15 K are found marginally affected by the dispersed mono and hybrid nanomaterials. Comparative experimental results presented here in on a variety of SNFs provide a guideline for their uses in developing soft condensed matter based innovative devices.

Theoretical Prediction of Electrical Conductivity Percolation of Poly(lactic acid)-Carbon Nanotube Composites in DC and RF Regime.

Polymer composites based on polylactic acid (PLA) reinforced with 0.25-5 wt.% of carbon nanotubes (CNTs) were synthesized by melt blending. The static (DC) and microwave (RF) electrical conductivity have been investigated on the PLA-CNT composites. The electrical percolation threshold has been theoretically determined using classical models of percolation in order to predict the conductivity of the different nanocomposites. Through the fitting process, it has been found that the percolation threshold is obtained at 1 wt.% of CNTs in the DC regime and reached below 0.25 wt.% of CNTs in the microwave regime. Among the Mamunya, McLachlan, or GEM models, the McCullough model remarkably fits the experimental DC and RF electrical conductivities. The obtained results are correlated to the electrical properties of a range of CNT-based composites, corresponding to the percolation threshold required for a three-dimensional network of CNTs into the polymer matrix.

Воздействие слабого импульсного магнитного поля на ионную проводимость суперионного проводника Pb-=SUB=-0.67-=/SUB=-Cd-=SUB=-0.33-=/SUB=-F-=SUB=-2-=/SUB=-

A magnetoconductometric effect was found under pulsed magnetic action (B = 0.1–1 T) on a single crystal of the superionic conductor Pb0.67Cd0.33F2 (cubic symmetry, space group Fm¯3m, unit cell parameter a = 5.7575 A). The static electrical conductivity σdc was determined from impedance spectra in the frequency range (5–5)×105 Hz. In the absence of magnetic influence (B = 0) the ionic conductivity of a superionic crystal is σdc = 1.4×10–4 S/cm. When applying a magnetic field (B = (0.1−1) T) it increases, reaching σdc = 9.5 10−4 S/cm and σdc(B)/σdc(0) = 6.8 at B = 1 T. The nature of the magnetoconductometric effect in the superionic Pb0.67Cd0.33F2 is discussed in connection with the features its atomic structure.

Элекрофизические свойства керамических твёрдых растворов Li0,03Na0,97TayNb1 – yO3 (у = 0,1 – 0,7) со структурой перовскита в области антисегнето-сегнетоэлектрического перехода

The electrophysical properties (dielectric permittivity, dielectric loss tangent, electrical conductivity) of Li0.03Na0.97TayNb1-yO3 (у = 0.1 – 0.7) ferroelectric solid solutions with the perovskite structure were studied. In the temperature range of 290 – 830 K, the investigated solid solutions undergo three phase transitions. The phase transitions are strongly smeared as the tantalum concentration increases. The Curie temperatures are established and it is shown that an increase in the concentration of tantalum leads to a decrease in this temperature. The values of the static electrical conductivity of ferroelectric solid solutions Li0.03Na0.97TayNb1 – yO3 (у = 0.1 – 0.7) and the activation enthalpies of charge carriers are determined.

Electronic Structure and Optical Properties of Cu2ZnSnS4 under Stress Effect

By using the pseudopotential plane-wave method of first principles based on density functional theory, the band structure, density of states and optical properties of Cu2ZnSnS4 under isotropic stress are calculated and analyzed. The results show that Cu2ZnSnS4 is a direct band gap semiconductor under isotropic stress, the lattice is tetragonal, and the band gap of Cu2ZnSnS4 is 0.16 eV at 0 GPa. Stretching the lattice causes the bottom of the conduction band of Cu2ZnSnS4 to move toward lower energies, while the top of the valence band remains unchanged and the band gap gradually narrows. Squeezing the lattice causes the bottom of the conduction band to move toward the high-energy direction, while the top of the valence band moves downward toward the low-energy direction, and the Cu2ZnSnS4 band gap becomes larger. The static permittivity, absorption coefficient, reflectivity, refractive index, electrical conductivity, and energy loss function all decrease when the lattice is stretched, and the above optical parameters increase when the lattice is compressed. When the lattice is stretched, the optical characteristic peaks such as the dielectric function shift to the lower-energy direction, while the optical characteristic peak position shifts to the higher-energy direction when the lattice is compressed.

Electrical Conductivity of Rubber Composites with Varying Crosslink Density under Cyclic Deformation.

Studies addressing electroconductive composites based on rubber have attracted great interest for many engineering applications. To contribute to obtaining useful materials with reproducible behavior, this study focused on understanding the mechanism of conductivity changes during mechanical deformation for rubber composites based on styrene-butadiene rubber (SBR) or ethylene-propylene-diene terpolymer (EPDM) vulcanized for various times. The composites were characterized by static electrical conductivity, tensile testing, dynamic mechanical thermal analysis (DMTA), and crosslink density measurements. The tensile strength and Young’s modulus were found to increase significantly with rising vulcanization time. Higher static conductivity values of the composites were observed with the increase in vulcanization time. The most important aspect of this investigation consisted in the electrical current measurement online with recording the stress-strain curves, revealing the details of the uniaxial cyclic deformation effect on changes in the structure of conductive pathways indirectly. The electrical conductivity during five runs of repeated cyclic mechanical deformations for SBR composites increased permanently, although not linearly, whereas EPDM composites showed a slight increase or at least a nearly constant current, indicating healing of minor defects in the conductive pathways or the formation of new conductive pathways.

Ab initio calculations for the transport properties of metals within Boltzmann transport theory: From equilibrium to nonequilibrium heating regime

The paper offers an approach to ab initio calculations for predicting the electron transport properties of solid-state metals in a case of nonequilibrium heating. Formulas for the electrical resistivity (also static conductivity) and thermal conductivity of metals at different electron and lattice temperatures were derived within a method proposed by Allen [Phys. Rev. B 17, 3725 (1978)] for the solution of the Boltzmann transport equation. The approach works well under equilibrium heating too when electron and lattice temperatures are equal. It performs most effectively if it is necessary to allow for the Fermi smearing of the electron distribution function over quantum states and the energy dependence of the electron-phonon spectral function. Four metals---Cu, Ag, Au and Pd---are considered as examples. We succeeded to reproduce well the temperature dependencies of electrical resistivity and thermal conductivity of studied metals in a wide range of temperatures under equilibrium heating. For the nonequilibrium regime of heating, calculations reproduce quite well the temporal evolution of the static electrical conductivity of gold, observed in recent experiments for the interaction of thin gold foils with ultrashort laser pulses.

Model-Based Correction of Temperature-Dependent Measurement Errors in Frequency Domain Electromagnetic Induction (FDEMI) Systems.

Data measured using electromagnetic induction (EMI) systems are known to be susceptible to measurement influences associated with time-varying external ambient factors. Temperature variation is one of the most prominent factors causing drift in EMI data, leading to non-reproducible measurement results. Typical approaches to mitigate drift effects in EMI instruments rely on a temperature drift calibration, where the instrument is heated up to specific temperatures in a controlled environment and the observed drift is determined to derive a static thermal apparent electrical conductivity (ECa) drift correction. In this study, a novel correction method is presented that models the dynamic characteristics of drift using a low-pass filter (LPF) and uses it for correction. The method is developed and tested using a customized EMI device with an intercoil spacing of 1.2 m, optimized for low drift and equipped with ten temperature sensors that simultaneously measure the internal ambient temperature across the device. The device is used to perform outdoor calibration measurements over a period of 16 days for a wide range of temperatures. The measured temperature-dependent ECa drift of the system without corrections is approximately 2.27 mSm−1K−1, with a standard deviation (std) of only 30 μSm−1K−1 for a temperature variation of around 30 K. The use of the novel correction method reduces the overall root mean square error (RMSE) for all datasets from 15.7 mSm−1 to a value of only 0.48 mSm−1. In comparison, a method using a purely static characterization of drift could only reduce the error to an RMSE of 1.97 mSm−1. The results show that modeling the dynamic thermal characteristics of the drift helps to improve the accuracy by a factor of four compared to a purely static characterization. It is concluded that the modeling of the dynamic thermal characteristics of EMI systems is relevant for improved drift correction.

Influence of gas-filled fracturеs on the electrical conductivity of coal at direct current

The article is devoted to the theoretical study of the influence of fractures on the static electrical conductivity of coal in order to develop and justify the non-destructive method for determining the fracturing of coal and other rocks that conduct electric current. The inability of the effective medium model to describe the behavior of fractures in rocks on a macroscopic scale and the complexity of experimental observations due to the low electrical conductivity of coal necessitates an additional theoretical study. In this paper, an approach is proposed that uses a hydrodynamic analogy between an electric current flowing around fractures and the motion of an ideal incompressible fluid in a potential flow around solids proposed earlier in our previous studies. The problem is reduced to solving a boundary value problem by the Cauchy-type integral method using the Sokhotsky-Plemel formulas. Integral dependences of the relative additional electrical resistance on the fracturing coefficient of the coal sample for an arbitrary ratio between the dimensions of coal sample and dimensions of fractures are found. The dependences of the additional electrical resistance on the fracturing coefficient of the coal sample were numerical calculated. Based on these calculations, the influence of the shape of cracks and the dimensions of a coal sample on the additional electrical resistance caused by fractures was analyzed. The nonlinear behavior of the dependence of the relative change in the additional electrical resistance of coal on the coefficient of fracturing and the thickness of the sample was established. It is shown that with an increase in the fracture coefficient, the growth of the electrical resistance of the sample occurs according to the root law, and further - according to the power law. An inverse relationship was established between the gaping of fractures and the electrical resistance of a coal sample. The results obtained can be used as a noninvasive method for determining the fracturing coefficient not only for coal, but also for other rocks that conduct electric current. Keywords: electrical resistance, coal sample, gas-filled cracks, hydrodynamic analogy, fracturing coefficient.

Электропроводность и структурная обусловленность ионного переноса в кристаллах лангасита La-=SUB=-3-=/SUB=-Ga-=SUB=-5-=/SUB=-SiO-=SUB=-14-=/SUB=-:Mn

The temperature dependence of the static electrical conductivity σdc(T) of a single crystal of lanthanum gallium silicate (langasite) La3Ga5SiO14 activated with an impurity of Mn (1000 ppm) has been studied by impedance spectroscopy. Impedance measurements of La3Ga5SiO14 (sp. gr. P321, Z = 1) were carried out along crystallographic axes a (double symmetry axis) and c (triple symmetry axis). It was found that the values of σ||a are significantly higher than the electrical conductivity σ||с, the anisotropy of the electrical conductivity is σ||a/σ||c = 170 at 773 K. The activation energy of electrotransport is Eσ = 0.75 ± 0.05 and 1.09 ± 0.02 eV along the a and c axes, respectively. The electrical conductivity mechanism has an ionic nature and an impurity character; oxygen vacancies VO•• are the most probable current carriers.

Electrical conductivity and structural conditionality of ion transfer in langasite La-=SUB=-3-=/SUB=-Ga-=SUB=-5-=/SUB=-SiO-=SUB=-14-=/SUB=-:Mn

The temperature dependence of the static electrical conductivity sigmadc(T) of a single crystal of lanthanum gallium silicate (langasite) La3Ga5SiO14 activated with an impurity of Mn (1000 ppm) has been studied by impedance spectroscopy. Impedance measurements of La3Ga5SiO14 (sp. gr. P321, Z=1) were carried out along crystallographic axes a (double symmetry axis) and c (triple symmetry axis). It was found that the values of sigma|| a are significantly higher than the electrical conductivity sigma|| c, the anisotropy of the electrical conductivity is sigma|| a/sigma|| c=170 at 773 K. The activation energy of electrotransport is Esigma=0.75±0.05 and 1.09±0.02 eV along the a and c axes, respectively. The electrical conductivity mechanism has an ionic nature and an impurity character; oxygen vacancies VOoo are the most probable current carriers. Keywords: lanthanum gallium silicate, langasite family, single crystal, electrical conductivity, anisotropy.

Dielectric spectroscopy studies of silver nanorod doped nematic liquid crystal

Dielectric spectroscopy provides information on molecular dynamics as well as on important material parameters such as the static dielectric permittivity (ε) and DC electrical conductivity (σ) of the bulk as well as at the interfaces. In this study, we present the dielectric spectroscopy results of silver nanorod doped nematic liquid crystal (NLC) in the frequency range of 20 Hz to 10 MHz. The relaxation frequencies tend to increase owing to the availability of free volume due to addition of nanorods. However, the conductivity (at 1 kHz) is observed to decrease with the increase in the nanorod concentration until aggregation of nanorods is observed in the NLC host. Dielectric strength of doped NLC samples also increases with increasing concentration of nanorods.

Electrical conductivity of a thin film in the case of an arbitrarily oriented ellipsoidal isoenergetic surface of a conductor

The static electrical conductivity of a thin conducting film is calculated using the kinetic approach. The model of diffuse boundary conditions is used as boundary conditions for the charge carrier distribution function. The isoenergetic surface of the conducting film material is an ellipsoid of rotation that is arbitrarily oriented in the pulse space. The volume of the conductor is dominated by scattering on impurity atoms and on dislocations of electrons (holes). The electrical conductivity of the film is analyzed depending on the angles that determine the direction of the ellipsoid axis of rotation, and a comparison with the results for the case of a macroscopic sample is presented. A comparison is made with experimental data for the electrical conductivity of Bi and Si thin films.

Hadronic transport coefficients from the linear σ model at finite temperature

We investigate general frameworks for calculating transport coefficients for quasiparticle theories at finite temperature. Hadronic transport coefficients are then computed using the linear sigma model (LSM). The bulk viscosity over entropy density ($\zeta/s$) is evaluated in the relaxation time approximation (RTA) and the specific shear viscosity ($\eta/s$) and static electrical conductivity ($\sigma_{el}/T$) are both obtained in the RTA and using a functional variational approach. Results are shown for different values of the scalar-isoscalar hadron vacuum mass with in-medium masses for the interacting fields. The advantages and limitations of the LSM for studies of strongly interacting matter out of equilibrium are discussed and results are compared with others in the literature.

Features of frequency dependence of electrical conductivity and dielectric properties in lignins from conifers and deciduous trees

Abstract Lignins are among the most common plant polymers and demonstrate pronounced electrical conductivity properties due to their conjugated polymolecular aromatic structure and polyfunctional nature. Electrical conductivity and dielectric properties of lignins from conifers and deciduous trees in the range of electric field frequencies from 10−2 to 107 Hz were investigated by means of dielectric spectroscopy. Characteristic parameters of static and high frequency electrical conductivity were calculated. To study the influence of the lignins functional nature on their electrophysical properties, the study determined three types of relaxators (separate charges or charge systems in the structure of a substance changing their position in space when exposed to an external alternating electric field) in the structure of the lignin macromolecule. Low-frequency relaxators are associated with oscillations of methoxyl groups. Mid-frequency relaxators correspond predominantly to phenolic hydroxyl groups and to hydroxyl groups of adsorbed water. High-frequency relaxators correspond to the hopping of π-electrons along the chain of conjugated bonds of a benzene ring. Differences in the structure and functional nature of lignins from conifers and deciduous trees cause different contributions of low-frequency relaxators. As a result, these features form differences in the electrophysical properties of lignins from conifers and deciduous trees.

Simulation of ab Initio Dynamics of the Formation of Metastable Conducting Solid Hydrogen

Density-functional theory (DFT) is applied to the calculation of the equation of state, the pair correlation function (PCF), and the static electrical conductivity of solid hydrogen near the transition point to the conducting state. It is found that the pressure versus density exhibits hysteresis at temperature of 100 K under compression followed by expansion. The overlapping of the isotherm branches of molecular and nonmolecular phases of solid hydrogen is observed, which corresponds to the domain of existence of metastable states. The value of this region is 275 GPa. Under compression, a transition of solid molecular hydrogen from monoclinic structure with C2/c symmetry to a conducting nonmolecular state with orthorhombic C2221 structure through an intermediate conducting molecular phase with orthorhombic Cmca-4 structure is observed. Under expansion, a transition of the conducting nonmolecular state with C2221 symmetry of the unit cell to a conducting molecular phase with Cmca-4 symmetry occurs through an intermediate nonmolecular phase with P21/c symmetry. It is shown that the conducting nonmolecular crystalline hydrogen with P21/c symmetry persists down to a pressure of 350 GPa.

Metastable Conducting Crystalline Hydrogen at High Pressure

The quantum molecular dynamics method within the density functional theory has been used to calculate the equation of state, pair correlation function, and static electrical conductivity of solid hydrogen in the region of formation of a conducting phase. Hysteresis has been revealed on the density dependence of the pressure at a temperature of 100 K under compression and subsequent tension. The overlapping of branches of the isotherms of the molecular and nonmolecular phases of solid hydrogen corresponds to the region of existence of metastable states. The width of this region is 275 GPa. It has been shown that conducting crystalline nonmolecular hydrogen with P21/c symmetry can exist at extension to a pressure of 350 GPa.

Phase States and Dielectric Properties of Li0.17Na0.83NbуТа1 –уO3 Ceramic Solid Solutions Prepared by High-Pressure, High-Temperature Synthesis

The electrical properties and phase states of Li0.17Na0.83NbуТа1 –уO3 (y = 0.1–0.5) ferroelectric perovskite solid solutions prepared by high-pressure, high-temperature synthesis have been studied using impedance spectroscopy. The e'(T) and σsv(T) curves of the solid solutions have been shown to have anomalies due to phase transitions of the materials. Their Curie temperature has been found to decrease with increasing Ta concentration. The static electrical conductivity of the solid solutions has been measured as a function of temperature and the enthalpies of activation of charge carriers in them have been evaluated. The Li0.17Na0.83Nb0.1Та0.9O3 solid solution has been shown to be a high-temperature superionic conductor. Possible mechanisms of the observed phenomena are discussed.

Contactless In Situ Electrical Characterization Method of Printed Electronic Devices with Terahertz Spectroscopy.

Printed electronic devices are attracting significant interest due to their versatility and low cost; however, quality control during manufacturing is a significant challenge, preventing the widespread adoption of this promising technology. We show that terahertz (THz) radiation can be used for the in situ inspection of printed electronic devices, as confirmed through a comparison with conventional electrical conductivity methods. Our in situ method consists of printing a simple test pattern exhibiting a distinct signature in the THz range that enables the precise characterization of the static electrical conductivities of the printed ink. We demonstrate that contactless dual-wavelength THz spectroscopy analysis, which requires only a single THz measurement, is more precise and repeatable than the conventional four-point probe conductivity measurement method. Our results open the door to a simple strategy for performing contactless quality control in real time of printed electronic devices at any stage of its production line.