Transverse Electrical Resistivity Research Articles

Coexistence of large anomalous Nernst effect and large coercive force in amorphous ferrimagnetic TbCo alloy films

The anomalous Nernst effect (ANE) has garnered significant interest for practical applications, particularly in energy harvesting and heat flux sensing. For these applications, it is crucial for the module to operate without an external magnetic field, necessitating a combination of a large ANE and a substantial coercive force. However, most materials exhibiting a large ANE typically have a relatively small coercive force. In our research, we have explored the ANE in amorphous ferrimagnetic TbCo alloy films, noting that the coercive force peaks at the magnetization compensation point (MCP). We observed that transverse Seebeck coefficients are amplified with Tb doping, reaching more than 1.0 μV/K over a wide composition range near the MCP, which is three times greater than that of pure Co. Our findings indicate that this enhancement is primarily due to direct conversion, a product of the transverse thermoelectric component and electrical resistivity. TbCo films present several significant advantages for practical use: a large ANE, the capability to exhibit both positive and negative ANE, the flexibility to be deposited on any substrate due to their amorphous nature, a low thermal conductivity, and a large coercive force. These attributes make TbCo films a promising material for advancing ANE-based technologies.

Effect of the thickness on electrical resistance of thin diamond-like carbon coatings on silicon substrate

The relationship between sp2/sp3-hybridizations ratio of atomic bonds in diamond-like carbon ( DLC --- Diamond-Like Carbon) and its electrical resistivity for coatings with a thickness in the range 22-70 nm prepared by vacuum arc deposition on silicon substrate of the KDB-8 brand has been established. It is established, that an increase in the coating thickness from 22 to 70 nm is accompanied by a decrease in the specific transverse electrical resistance of samples from 17 to 2 GΩ·m. This effect is explained by an increase in the proportion of carbon atoms with sp2-hybridization of electronic orbitals from 86 to 91%, which leads to the appearance of an additional number of π-bonds. A mathematical model, describing the spatial distribution of current when measuring transverse I-V characteristic, has been developed. The results obtained will be useful in creating resistive layers on the electrodes of gas-discharge detectors of charged particle to limit the amount of current in the event of rare spark discharges inside them caused by the registration of random highly ionizing particles. Keywords: ( DLC), electrical properties of thin films, hybridization of electronic orbitals, Raman scattering, I-V characteristic.

Влияние толщины на удельное электросопротивление тонких покрытий из алмазоподобного углерода на кремнии

The relationship between sp^2/sp^3 hybridizations ratio of atomic bonds in diamond-like carbon (DLC) and its electrical resistivity for coatings with a thickness in the range 22-70 nm prepared by vacuum arc deposition on silicon substrate of the SHB-8 brand has been established. It is established, that an increase in the coating thickness from 22 to 70 nm is accompanied by a decrease in the specific transverse electrical resistance of samples from 17 to 2 GOhm·m. This effect is explained by an increase in the proportion of carbon atoms with sp^2 hybridization of electronic orbitals from 86 to 91%, which leads to the appearance of an additional number of π-bonds. A mathematical model, describing the spatial distribution of current when measuring transverse I-V characteristic, has been developed. The results obtained will be useful in creating resistive layers on the electrodes of gas-discharge detectors of charged particle to limit the amount of current in the event of rare spark discharges inside them caused by the registration of random highly ionizing particles.

Resistividad eléctrica de la madera de Pinus pseudostrobus, Tabebuia rosea y Quercus scytophylla

The objective of the research was to determine the electrical resistivity of the wood of Pinus pseudostrobus, Tabebuia rosea and Quercus scytophylla in the directions of anisotropy. For this, 20 solid wood specimens of each of the species with dimensions of 20 mm × 20 mm × 20 mm in the radial, tangential and longitudinal directions, respectively, were prepared, and the density and moisture content of the wood were determined. wood. To carry out the electrical resistivity tests, the electrical resistance was measured using direct current with a test voltage of 1000 volts. Moisture content was for P. pseudostrobus 12,6 %, for T. rosea 10,6 % and for Q. scytophylla 15,6 %. The average transverse electrical resistivity was for P. pseudostrobus 45,5 MΩ m, for T. rosea 10,3 MΩ m and for Q. scytophylla 61,4 MΩ m. The longitudinal electrical resistivity was for P. pseudostrobus 24,7 MΩ m, for T. rosea 2,.2 MΩ m and for Q. scytophylla 19,6 MΩ m. The magnitudes of the longitudinal resistances measured in the three woods are similar to those of the woods reported in the literature. Another finding was that the resistivity values show differences between the anisotropy directions of the wood and between the species studied.

Anisotropic thermal and electrical conductivities of individual polyacrylonitrile-based carbon fibers

Understanding the anisotropy of thermal and electrical properties of carbon fibers is important for many applications, but transverse transport properties are difficult to measure. We apply time-domain thermoreflectance (TDTR) mapping to determine spatial variations in the transverse thermal conductivity for different radial positions for two polyacrylonitrile (PAN)-based carbon fibers, the IM7 and AS4 fibers. Single-point TDTR measurements determine the longitudinal and transverse thermal conductivities of the carbon fibers. The transverse and longitudinal electrical resistivities of the AS4 fibers are determined by the van der Pauw method and four-point method, respectively. The transverse thermal conductivity of IM7 fibers is approximately uniform (2.0 W/m-K) at different radial positions. In contrast, the transverse thermal conductivity of the core (3.0 W/m-K) in AS4 fibers is higher than the shell (2.4 W/m-K). The longitudinal thermal conductivity of IM7 fibers is 7.5 W/m-K and the value of AS4 fibers is 6.9 W/m-K. The transverse electrical resistivity of AS4 fibers is 6.3 × 10−5 Ωm and the longitudinal electrical resistivity is 1.5 × 10−5 Ωm; the electrical resistivities of IM7 fibers were reported previously. Both the thermal and electrical measurements indicate a larger anisotropy of the IM7 fiber than the AS4 fiber.

Single carbon fiber transverse electrical resistivity measurement via the van der Pauw method

Although the electrical properties of carbon fibers and carbon fiber composites are critical to the design of composite materials, a direct measurement of the transverse electrical resistivity of a single carbon fiber has not yet been reported. Significant challenges arise in fabricating specimens and making electrical resistance measurements due to the geometry and small diameter of a single carbon fiber (about 4–7 μm). In this study, we report a specimen design and fabrication technique for measuring the transverse electrical resistance of an individual carbon fiber by the van der Pauw method. IM7 carbon fiber specimens are fabricated by a combination of photolithography and the focused ion beam. Specimen thickness, which is required for resistivity calculations, is measured by atomic force microscopy. We measure mean transverse electrical resistivity of (9.3 ± 0.3) × 10−5 Ω m, which is roughly six times greater than the reported longitudinal values. Our measurement technique can be applied to a range of conductive fibers. More accurate measurements of the electrical conduction in carbon fibers are critical for applications such as electromagnetic interference shielding, structural health monitoring, and lightning strike protection.

Effects of Electropulsing Treatment on Microstructure and Properties of Cemented Carbide (WC-15Co)

Electropulsing treatment (EPT) is a promising postprocessing method to optimize microstructure. In the present work, the EPT was applied to treat cemented carbide (WC-15Co). The electropulse-induced microstructural evolution in WC-15Co was investigated. Compared with the untreated sample, the transverse rupture strength and electrical resistance of the treated sample were reduced. However, there was no significant change in the scanning electron microscopy (SEM) microstructure. Therefore, electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM) were carried out to detail the microstructural evolution. This process revealed that electropulsing could promote the recrystallization and the transition of e-Co to α-Co, as well as the evolution of microstructure. In addition, the dislocations in the treated sample were significantly fewer than those in the untreated sample.

Evolution of the transverse electrical resistivity of YBa2Cu3O7–δ single crystals under irradiation with high-energy electrons

The effect of irradiation with high-energy electrons on the transverse electrical resistivity of YBa2Cu3O7–δ single crystals with a high degree of perfection that are optimally doped with oxygen is considered. This irradiation creates macroscopic regions oriented along the layers in the sample, which are characterized by oxygen deficiency, leading to variable-range hopping transverse conductivity. An increase in the dose of irradiation leads to a decrease in the region of localization of charge carriers.The effect of irradiation with high-energy electrons on the transverse electrical resistivity of YBa2Cu3O7–δ single crystals with a high degree of perfection that are optimally doped with oxygen is considered. This irradiation creates macroscopic regions oriented along the layers in the sample, which are characterized by oxygen deficiency, leading to variable-range hopping transverse conductivity. An increase in the dose of irradiation leads to a decrease in the region of localization of charge carriers.

Transverse Electrical Resistivity Evaluation of Rod Unidirectional Carbon Fiber-Reinforced Composite Using Eddy Current Method

This paper proposes a simple approach to evaluate a transverse electrical resistivity of a rod unidirectional carbon fiber-reinforced composites (UD-CFRCs). The method is based on eddy current technique. The model is associated with inverse problem method that consists of minimizing the difference between the computed and measured resistances. The ant colony algorithm which is a kind of heuristic minimizing algorithm based on population exploration is used to get transverse electrical resistivity. The findings of the work are summarized as the following. First, it was demonstrated that the induced power in the UD-CFRC and the resistance of the coil are independent of the value of longitudinal resistivity. Then, the electrical resistance is computed using direct problem which is formulated with the 2-D axisymmetric finite-element method. After that, the identified resistivity, which obtained with the inverse problem, is introduced in the direct problem to compute resistance. Finally, the confrontation between the computed resistance and the measured one shows a significant concordance between the two.

Transverse resistance in HoBa2Cu3O7−δ single crystals

The transverse electrical resistance of HoBa2Cu3O[Formula: see text] single crystals is investigated in the temperature range [Formula: see text] for optimally-doped [Formula: see text] and oxygen-poor [Formula: see text] samples. With decreasing temperature, the resistivity of the optimally-doped samples has been found to transit from the regime of scattering on phonons and defects to the regime of “semiconductor” character and, near [Formula: see text], of the fluctuation conductivity. The oxygen-poor samples have been revealed to exhibit only a variable range hopping conductivity of “semiconductor” character, which near [Formula: see text] transits into the fluctuation conductivity. A significant anisotropy of the residual resistivity and characteristics of the fluctuation conductivity is observed for samples of both types.

Electrical resistivity prediction of dry carbon fiber media as a function of thickness and fiber volume fraction combining empirical and analytical formulas

The transverse electrical resistivity of the dry unidirectional carbon fiber preforms was studied experimentally taking into consideration various parameters. The dependency of the electrical resistivity transverse to the fibers was thoroughly experimentally studied as a function of the preform thickness and the fiber volume fraction. Empirical mathematical relations were extracted and combined with a non-linear compaction semi-analytical formula. The extracted formula consolidates the compressibility of the preform material, the preform thickness and the fiber volume fraction or the applied pressure in order to calculate the electrical resistivity of the unidirectional preform material transverse to the fibers. Two electrical resistance measurements, at two different thicknesses and two electrical resistance measurements, at two different pressure levels, are necessary to obtained, in order to predict the full range of the electrical resistivity values of the preform material transverse to the fibers as a function of thickness and fiber volume fraction. Very good agreement between the proposed formulas and the experiments has been obtained.

Transverse resistance of YBa2Cu3O7−δ single crystals

Measured is the transverse electrical resistance of YBa2Cu3O7−δ single crystals with different oxygen deficiency values (δ) in the temperature range Tc−300K. The experimental data are approximated by an empiric expression accounting for the fluctuation conductivity near Tc and the semiconductor-like resistance regime. Our analysis of the concentration dependences of the fitting parameters, in particular, reveals that the resistance temperature dependence is largely affected by the sample's non-homogeneity. The latter, in turn, causes a Tc anisotropy and variable-range hopping conductivity between different phases. The deduced maximal values of the basal-plane coherence length, ξxy(0), are comparable with those for low-temperature superconductors.

Transverse resistance in Y1−yPryBa2Cu3O7−δ at large praseodymium concentrations

The effect of praseodymium doping on the transverse electrical resistance of Y1−yPryBa2Cu3O7−δ single crystals is investigated by electrical resistance measurements. The resistance curves can be fitted well to an expression accounting for the thermo-activated variable-range hopping charge transfer in conjunction with the fluctuation conductivity in the 3D Aslamazov–Larkin model. Our analysis of the Pr concentration dependence of the fitting parameters shows that in the concentration range 0.34<y<0.43 the sample is breaking up into separate conducting regions (granules) and the conductivity acquires a character peculiar to the variable-range hopping mechanism. With increasing Pr concentration the contribution of electron scattering on impurities monotonically increases, while the region of superconducting fluctuations shrinks away. A pronounced anisotropy of the coherence length has been observed, revealing the Cooper pairs size in the direction across the layers to be two orders of magnitude smaller than its in-plane value.

Experimental and numerical analysis of interfilament resistances in NbTi strands

Superconducting strands are composite wires made of fine superconducting filaments embedded in a metallic matrix. The transverse resistivity among superconducting filaments affects the coupling losses during electromagnetic transients and the electro-thermal behavior of the wire in case of a quench. A direct measurement of the transverse interfilament resistance as a function of temperature in NbTi multi-filamentary wires was performed at the ENEA Frascati Superconductivity Division, Italy by means of a four-probe method. The complexity of these measurements is remarkable, due to the current distribution phenomena that occur among superconducting filaments during these tests. A two-dimensional finite element method model of the wire cross section and a three-dimensional electrical circuit model of the wire sample developed at the University of Bologna are applied here to derive qualitative and quantitative information about the transverse electrical resistance matrix. The experiment is aimed at verifying the qualitative behaviors and trends predicted by the numerical calculations, especially concerning the current redistribution length and consequent length effects of the sample under test. A fine tuning of the model parameters at the filament level allowed us to reproduce the experimental results and get quantitative information about the current distribution phenomena between filaments.

Experimental and Theoretical Analysis of Transverse Resistances in a $\hbox{Nb}_{3}\hbox{Sn}$ LMI-EM Strand

In Nb3Sn strands, hundreds or thousands of fine superconducting filaments are embedded in a metallic matrix for thermal and electrical stabilization. The transverse electrical resistivity between filaments plays a fundamental role in determining the ac losses, the thermal stability, and the current transfer length of the wire. The direct measurements of the transverse electrical resistances give useful information both for stability computations and to analyze the mechanical performance of the wire. In this paper, the interfilament resistances measured with a four-probe technique on a Nb3Sn wire produced by Europa Metalli have been interpreted through a simulation code. A 2-D finite element method model of the wire cross-section and of a 3-D electrical circuit model of the wire sample have been applied to derive qualitative and quantitative information about the transverse electrical resistance matrix. A comparison with measurements performed on a Nb3Sn wire with a different configuration shows the relevance of the wire layout in determining the interfilament resistance between filament bundles.

Evaluation of Electrical Properties of Cr/CrN Nano-Multilayers for Electronic Applications

The electrical properties of Cr/CrN nano-multilayers produced by Unbalanced Magnetron Sputtering have been studied as a function of bilayer period and total thickness. Two groups of multilayers were produced: in the first group the bilayer period varied between 20 nm, 100 nm and 200 nm with total thickness of 1 microm, and in the second group the bilayer period varied between 25 nm, 50 nm and 100 nm and a total thickness of 100 nm. X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) were used in order to investigate the microstructure characteristics of the multilayers, and the Four Point Probe (FPP) method was used to evaluate in-plane and transverse electrical resistivity. XRD results show (111) and (200) orientations for all the CrN coatings and the presence of a multilayer structure was confirmed through SEM studies. Transverse electrical resistivity results show that this property is strongly dependent on the bilayer period.

Analysis of Transverse Resistance Measurements in ${\rm Nb}_{3}{\rm Sn}$ Superconducting Wires

The superconducting wires are generally made of several hundreds or thousands of fine superconducting filaments embedded in a metallic matrix. Several relevant properties of the superconducting wires depend on the transverse resistances between filament bundles. In Nb3Sn wires realized with Bronze Route or Internal Tin technology, the presence of the bronze matrix can determine a significant increase of the transverse interfilament resistance with respect to wires with copper matrix. This increased resistivity in turn plays a role in determining the ac losses, thermal stability, and sensitivity to mechanical bending of the wire. The direct measurements of the transverse electrical resistances give useful information both for stability computations and to analyze the mechanical performance of the wire. The complexity of these measurements is however remarkable, due to the current distribution phenomena that occur among superconducting filaments during these tests. This paper presents the application of a 2D FEM model of the wire cross section and of a 3D electrical circuit model of the wire sample to derive qualitative and quantitative information about the transverse electrical resistance matrix. The paper shows that a detailed qualitative and quantitative description of the measurement results can only be obtained by means of a 3D model, that allows computing the current distribution along and across the sample length during the measurements.

Inter-tube bonding, graphene formation and anisotropic transport properties in spark plasma sintered multi-wall carbon nanotube arrays

Millimeter long, vertically oriented, multi-walled carbon nanotube (MWCNT) arrays were pre-aligned and densified using spark plasma sintering (SPS) technique to form aligned MWCNT bulk samples. The combined results of X-ray powder diffraction, Raman spectroscopy, scanning electron microscopy and high-resolution transmission electron microscopy show that the MWCNTs largely retain their orientation and individual tubular morphology in the aligned MWCNT bulk samples, and that the SPS process induces inter- and intra-tubular bonding as well as graphene formation. In view of the one-dimensional nature of individual MWCNTs, it is particularly noteworthy that the transverse electrical resistivity ρ T is slightly lower than the longitudinal resistivity ρ L , whereas the transverse thermal conductivity κ T is ∼50% of κ L . The room temperature κ L is ∼31 W/(m K), one of the highest reported in MWCNT bulk samples. In addition, the thermopower measurements show anisotropy and features of phonon drag.

Modeling of mechanical damage detection in CFRPs via electrical resistance

Carbon fiber reinforced polymer composites (CFRPs) are inherently multifunctional materials that, in addition to their primary function as a structural material, allow for the sensing and monitoring of in situ damage nucleation and evolution by the measurement of the material electrical resistance. Here an analytic model is developed for the transverse (perpendicular to the fibers) electrical resistance of pristine and damaged unidirectional composites, complementing earlier work on the longitudinal resistance. The ratio of transverse to longitudinal resistance for undamaged materials provides a direct measure of the internal density of fiber–fiber electrical contacts, a key material parameter in linking to the response of damaged materials. Under uniaxial loading with evolving fiber breakage, the normalized transverse resistance versus strain is predicted to have exactly the same form as that for the longitudinal resistance. Numerical studies show this agreement for uniform fiber–fiber contact distributions but, for random contact distributions, the longitudinal resistance is larger than predicted while the transverse resistance is smaller; these differences are shown to arise as a result of the statistically-preferential breaking of longer fiber segments. Analysis of multiple numerical simulations shows that variations in the electrical resistance are not directly correlated with variations in the stress–strain response. Thus, statistical methods are required to relate resistance to strain or damage. The Weibull modulus of the resistance change increases with increasing applied strain, with values exceeding 10 and 20 for the transverse and longitudinal resistance, respectively, demonstrating increasing reliability at higher damage levels and good correlation of average resistance change to applied strain. The present study shows that both longitudinal and transverse resistance changes are sensitive to damage in a predictable manner and can be used together to improve the reliability of damage assessment during loading of CFRPs.

Oxide barriers and their effect on AC losses of Bi,Pb(2223) multifilamentary tapes

The transverse electrical resistivity in multifilamentary Ag/Bi, Pb(2223) tapes is considerably enhanced after introducing inert oxide barriers, a new concept in which each single filament is surrounded by a highly resistive BaZrO/sub 3/ layer of 100 Hz. This corresponds to a marked lowering of AC coupling losses. The highest critical current density of these tapes is actually 15000 A/cm/sup 2/ at 77 K, 0 T, i.e. still below that of our tapes without barriers (35000 A/cm/sup 2/). The fabrication processes leading to Bi,Pb(2223) tapes with oxide barriers is described, with an emphasis on new deformation processes developed in our laboratory for the fabrication of long multifilamentary Bi,Pb(2223) tapes, comprising four roll (or two-axes) rolling and periodic pressing. The developed tapes with oxide barriers are promising in view of their use in transformers and cables.