Electrical Charge Transport Research Articles

Anisotropic charge transport in strongly magnetized relativistic matter

We investigate electrical charge transport in hot magnetized plasma using first-principles quantum field theoretical methods. By employing Kubo’s linear response theory, we express the electrical conductivity tensor in terms of the fermion damping rate in the Landau-level representation. Utilizing leading-order results for the damping rates from a recent study within a gauge theory, we derive the transverse and longitudinal conductivities for a strongly magnetized plasma. The analytical expressions reveal drastically different mechanisms that explain the high anisotropy of charge transport in a magnetized plasma. Specifically, the transverse conductivity is suppressed, while the longitudinal conductivity is enhanced by a strong magnetic field. As in the case of zero magnetic field, longitudinal conduction is determined by the probability of charge carriers to remain in their quantum states without damping. In contrast, transverse conduction critically relies on quantum transitions between Landau levels, effectively lifting charge trapping in localized Landau orbits. We examine the temperature and magnetic field dependence of the transverse and longitudinal electrical conductivities over a wide range of parameters and investigate the effects of a nonzero chemical potential. Additionally, we extend our analysis to strongly coupled quark-gluon plasma and study the impact of the coupling constant on the anisotropy of electrical charge transport.

Controllability of optical, electrical, and magnetic properties of synthesized Cd-doped MgFe2O4 nanostructure

This study explores the synthesis of cadmium-magnesium co-doped magnesium ferrite (Mg1+xCdxFe2–2xO4, 0.00 ≤ x ≤ 0.30, Δx = 0.05) via a citric acid-assisted sol-gel auto-combustion method. X-ray diffraction (XRD) analysis revealed crystal structure changes due to Cd and Mg co-doping, with the 0.25 Cd sample showing the smallest crystallite size and highest lattice strain. High-resolution transmission electron microscopy (HRTEM) confirmed the nanostructure and largest surface area for this sample. Diffuse reflectance spectra, analyzed using the Kubelka-Munk relation, indicated that the 0.25 Cd sample had the lowest energy gap (2.08 eV), supported by band position calculations. Electrical conductivity and charge transport mechanisms were examined at various temperatures. Magnetization studies showed reduced saturation magnetization at x = 0.25, ascribed to cation distribution changes and spin canting, with coercivity and anisotropy decreasing with higher Cd content. Overall, the 0.25 Cd sample exhibited optimized optical, electrical, and magnetic properties due to its distinct microstructure.

Evolution from micropinned to polymeric alloy structure of XLPE‐PS: Improving electrical properties and mechanism

AbstractThis research investigates the transition from a micropinned to a polymeric alloy structure in crosslinked‐polyethylene‐polystyrene (XLPE‐PS). Incorporating 2 wt% 10 μm PS particles into low‐density polyethylene (LDPE) and crosslinking with 2 wt% dicumyl peroxide (DCP) forms XLPE‐PS structures. The polymeric alloy structure, formed at 220°C extrusion, contrasts with the micropinned formed at 150°C. Morphological, thermo‐structural, chemical, and crystal properties are examined to understand their impact on electrical properties and charge transport mechanisms. Results indicate that the polymeric alloy effectively resolves void/crack issues, whereas the micropinned exhibits phase separation. Both structures exhibit a benzene‐crosslinked network, and variations in these structures lead to significant changes in thermo‐structural, chemical, and crystalline properties. The polymeric alloy XLPE‐PS shifts the polyethylene (PE) hkl crystal planes, confirming phase shift and optimal alloying. The structural alterations reveal deeper traps and higher densities in the polymeric alloy XLPE‐PS, leading to significantly improved electrical properties, including reduced DC conductivity by up to 1.3 and 0.7 decades at 30 and 90°C, and increased DC breakdown strength by up to 40.34% and 16.17% at 30 and 90°C, respectively, compared with micropinned XLPE‐PS. This research offers insights into stable high‐voltage insulation development.

Insights into the ternary substitution Na2.96+xK0.04 V2-xNix(PO4)2.98F0.06 with superior rate capability and near-zero strain property

Na3V2(PO4)3 (NVP) is considered the most favorable cathode for sodium-ion batteries due to its solid NASICON skeleton. Nevertheless, poor intrinsic conductivity is insufficient for its further commercialization. In this paper, we present a promising K/Ni/F co-doped and carbon nanotubes (CNTs) encapsulated Na2.96+xK0.04 V2-xNix(PO4)2.98F0.06 (KNF@CNTsx) cathode materials. The synthesis of KNF@CNTsx is achieved using a facile sol-gel method. The replacement of Na+ with K+ broadens the migratory pathway and supports the crystal skeleton, while F− substitution reduces the average grain dimension, thereby increasing the diffusion rate of Na+. Furthermore, the reduction of resistance by Ni2+ doping enables optimization of the transport of electrical charge, while also facilitating the optimization of chemically-defined properties. Concurrently, the optimal quantity of carbon capping and wrapping of CNTs facilitate the formation of efficacious conductive network, which diminishes the size of grains and shortens the pathway for the diffusion of Na+. This network could also serve as a buffer against crystal deformation. In conclusion, the modified KNF@CNTsx samples exhibit notable enhancements in their conductivity, ion diffusion capacity, and structural stability. Among them, the KNF@CNTs0.04 sample exhibits a capacity for reversibility of 93.3 mAh g−1 at 50C, with a remaining capacity of 68.5 mAh g−1 after 4000 successive long charge-discharge cycles. Ex-situ electrochemical XRD demonstrates the V3+/V4+ redox reaction occurs accompanied by the phase transfer reaction, during which Na+ prefers to diffuse along c-axial in the crustal structure. Moreover, volume alteration of this KNF@CNTs0.04 cellular entity is miniscule and reversible during the charge-discharge process, further confirming the stabilized construction and near-zero strain property. The after-cycled XRD/SEM/XPS certify the improved chemical and structural stability of KNF@CNTs0.04, indicating the constructive effects of K/Ni/F ternary substitution.

Broadband Dielectric Spectroscopy: Unraveling Na+diffusion and mixed conduction in Na₂O-modified zinc phosphate glasses for electrode material applications

The fundamental understanding of electric charge (ion + polarons/electrons) transport and relaxation mechanism is essential for applications in solid state ionics. In present work, to study Na+ transport, the electrical conductivity of zinc phosphate glasses modified with Na2O has been investigated in temperature range 313K and 473K and frequency range of 100 mHz to 1 MHz. The experimental data of Nyquist plots is fitted with appropriate equivalent circuits at different temperatures which reveals presence of mixed conduction (polaronic + ionic) and Na+ diffusion (at 50 mol% Na2O) in studied glass samples. The values of frequency exponent (s) obtained from the fitting of experimental data of the real part of electrical conductivity with Almond–West equation (WAE) have been used to determine the conduction mechanism. The electric transport in studied glasses occurred via correlated barrier hopping and non-overlapping small polaron tunnelling conduction models depending on the glass composition and temperature range of investigation. Electric Modulus studies further supports the assertion of composition and temperature dependent conduction mechanisms. The activation energies determined from conductivity, electric modulus, and impedance measurements are found to be consistent, indicating a good correlation in the study.

Evolving Synergy Between Synthetic and Biotic Elements in Conjugated Polyelectrolyte/Bacteria Composite Improves Charge Transport and Mechanical Properties.

gLiving materials can achieve unprecedented function by combining synthetic materials with the wide range of cellular functions. Of interest are situations where the critical properties of individual abiotic and biotic elements improve via their combination. For example, integrating electroactive bacteria into conjugated polyelectrolyte (CPE) hydrogels increases biocurrent production. One observes more efficient electrical charge transport within the CPE matrix in the presence of Shewanella oneidensis MR-1 and more current per cell is extracted, compared to traditional biofilms. Here, the origin of these synergistic effects are examined. Transcriptomics reveals that genes in S. oneidensis MR-1 related to bacteriophages and energy metabolism are upregulated in the composite material. Fluorescent staining and rheological measurements before and after enzymatic treatment identified the importance of extracellular biomaterials in increasing matrix cohesion. The synergy between CPE and S. oneidensis MR-1 thus arises from initially unanticipated changes in matrix composition and bacteria adaption within the synthetic environment.

Effective Coupling Model to Treat the Odd-Even Effect on the Current-Voltage Response of Saturated Linear Carbon Chains Single-Molecule Junctions.

The calculation of the electrical charge transport properties of alkanes C n H 2n S 2 with (n = 4-11) was performed to understand the odd-even effect on its current-voltage response. The extended molecule and broadband limit models were used to describe the molecular junction and covalent coupling with the electrodes. It was shown that among the participating molecular orbitals, HOMO and HOMO-1 are the ones with the most charge transport contribution. Moreover, the odd-even effect is caused by the alternation of the eigenvalues of some frontier orbitals as a function of the number of carbons, especially the HOMO that dominates the electrical transport. It could also be noted that when the current is analyzed outside the resonance, the relationship with the number of carbons exponentially decays, confirming the reports in the literature. To the best of our knowledge, a first principle study of the odd-even effect in symmetric systems composed by linear saturated carbon chains covalently coupled to electrodes has not been reported yet.

Multifunctional features of rare-earth based perovskite-like ferrocobaltite Eu(Fe0.5Co0.5)O3

Currently, the search for new materials that allow the electronic manipulation of spin for the transport of both electric charge and spin has intensified, since their applications in spintronic devices depend on this adjustment. The aim of this work is the analysis of the crystallographic properties and their correlation with the semiconducting ferromagnetic response of the compound Eu(Fe0.5Co0.5)O3 synthesised by solid reaction. It is observed that this material crystallizes forming an orthorhombic structure (Pnma space group) with disorder in the distribution of Fe and Co ions. Optical evaluation shows a bandgap of 1.15 eV, typical in semiconductors, which is corroborated by electrical transport measurements. Magnetic characterization reveals a predominantly antiferromagnetic behaviour in the low temperature regime, while at high temperatures a soft ferromagnetic response predominates as results of super-exchange interactions between magnetic moments. First-principles electronic structure calculations suggest the occurrence of direct semiconductor-type band gap but of different value for the two orientations spin up and spin down. This result allows inferring the technological applicability of the material in devices based on polarized spin currents.

Perspectives of miniaturization of β-Ga2O3 devices with graphene electrodes

Micrometer-scale circular graphene/β-Ga2O3 structures are fabricated by transferring graphene layers to (2‾01) and (010) bulk gallium oxide substrates. Focused ion beam etching is used to downscale the area of the graphene/β-Ga2O3 junctions, and a nanoprobe-based approach is employed for their electrical characterization in the chamber of the scanning electron microscope. Using this approach, the impact of defects in graphene on the electrical characteristics of the junctions is suppressed. A significant difference between the structures fabricated on (2‾01) and (010) gallium oxide surfaces is further demonstrated. By numerical fitting of the measured data, several electric charge transport mechanisms are distinguished depending on the applied bias and orientation of the gallium oxide surface.

Investigation of the role of charge injection and Coulomb force during the melting of phase-change materials under constant temperature boundary conditions

This paper presents an investigation of the melting of dielectric material in a rectangular cavity under the effect of electrohydrodynamics (EHD). First, phase-change modeling is implemented to simulate the melting performance of paraffin wax without EHD under constant temperature boundary conditions until a steady-state condition is achieved. Next, the whole set of coupled EHD equations is introduced to the model, with the Coulomb force using a Heaviside function for charge injection being the only electrical body force considered. Finally, the numerical model is implemented using the finite element method to solve for the electric field, flow field, temperature field, and charge transport. The numerical results show that, under the effect of EHD, melting continues due to the generation of electroconvection cells in the liquid phase-change material and the flow field manifests as two symmetric rotational cells generated between every two successive electrodes. The flow field causes the redistribution of the temperature field in the liquid bulk, which enhances the heat transfer. Melting continues until a steady-state condition is almost reestablished after about one hour. The enhancement factor, defined as the ratio of the EHD melt thickness to the steady-state melt thickness without EHD, is 2.33 at 6 kV applied voltage.

Tuning the crystalline orientation of quasi 1D anisotropic Sb2Se3 as a function of growth temperature for thin film photovoltaic applications

Antimony selenide (Sb2Se3) shows excellent photon absorption in the visible region and hence gaining tremendous attention from the last decade for thin film photovoltaics. Also, it has unique one-dimensional crystal structure and simple binary composition. However, the growth of Sb2Se3 thin films with its predominant orientation along [hk1] to make use of easy electrical charge transport seems challenging due to various governing growth parameters. In this work, we have studied the role of growth temperature (between 200 ℃ and 320 ℃) in the crystalline orientation of Sb2Se3 thin films on glass substrates via close-space thermal evaporation. In addition to growth orientation, we have investigated the effect of growth temperature on the surface morphology, elemental composition, film thickness, and optical properties of Sb2Se3 thin films. Electrical properties and photoresponse were measured on [hkl] and [hk0] oriented films to understand the effect of anisotropy and it is inferred that [hk1] oriented film as a favorable one for the charge transport. Also, the photoresponse results showed fair photoconductance under white light illumination and zero applied bias.

Tracing baryon and electric charge transport in isobar collisions

It is of fundamental interest to understand the carrier of conserved quantum charges within protons and nuclei at high energy. Preliminary data from isobar collisions at RHIC reveal a scaled net-baryon to net-electric charge ratio (B/ΔQ × ΔZ/A) at midrapidity between 1.2 and 2, consistent with string junction model predictions. Here, we compute the initial stage scaled net-baryon to net-electric charge ratio for isobar collisions. Our model incorporates a realization of the string junction model and models the nuclear structure. Our predictions identify the baseline expectations for such measurement and quantify the impact of the nuclear structure.

Ti3C2Tx MXene reinforcement: a nickel-vanadium selenide/MXene based multi-component composite as a battery-type electrode for supercapacitor applications.

Designing innovative microstructures and implementing efficient multicomponent strategies are still challenging to achieve high-performance and chemo-mechanically stable electrode materials. Herein, a hierarchical three-dimensional (3D) graphene oxide (GO) assisted Ti3C2Tx MXene aerogel foam (MXene-GAF) impregnated with battery-type bimetallic nickel vanadium selenide (NiVSe) has been prepared through a hydrothermal method followed by freeze-drying (denoted as NiVSe-MXene-GAF). 3D-oriented cellular pore networks benefit the energy storage process through the effective lodging of NiVSe particles, improving the access of the electrolyte to the active sites, and alleviating volume changes during redox reactions. The 3D MXene-GAF conductive matrix and heterostructured interface of MXene-rGO and NiVSe facilitated the rapid transport of electrical charges and ions during the charge-discharge process. As a result of the synergism of these effects, NiVSe-MXene-GAF exhibited remarkable electrochemical performance with a specific capacity of 305.8 mA h g-1 at 1 A g-1 and 99.2% initial coulombic efficiency. The NiVSe-MXene-GAF electrode delivered a specific capacity of 235.1 mA h g-1 even at a high current density of 12 A g-1 with a 76.8% rate performance. The impedance measurements indicated a low bulk solution resistance (Rs = 0.71 Ω) for NiVSe-MXene-GAF. Furthermore, the structural robustness of NiVSe-MXene-GAF guaranteed long-term stability with a 91.7% capacity retention for successive 7000 cycles. Thus, developing NiVSe-MXene-GAF provides a progressive strategy for fabricating high-performance 3D heterostructured electrode materials for energy storage applications.

Charge transport in electrospinning of polyelectrolyte solutions.

This study elucidates the electrical charge transport during electrospinning of weak polyelectrolyte (poly(acrylic acid) (PAA)) solutions by employing current emission measurements. With pH variation, the PAA ionization degree could be controlled from uncharged at low pH to weakly charged at intermediate solution pH. Electrospinning neutral poly(vinylpyrrolidone) (PVP) as a reference polymer solution confirmed established current-flow rate scaling relationships as shown by De La Mora and Loscertales (1994), I ∼ (γKQ)ν, independent of the applied electric field polarity, where ν = 0.5, K is the conductivity, γ is the surface tension, Q is the flow rate, and I is the current. Similarly, the uncharged PAA did not display any polarity dependence, yet ν ≈ 0.8. Negatively charged PAA, however, showed a marked deviation in the current-flow rate behavior, which was affected by the applied electric field polarity. In the case of negative polarity, ν = 0.99, whereas for a positive polarity ν = 0.68. Similarly, the voltage required for stable cone-jet electrospinning of charged PAA was significantly higher in the negative polarity configuration for all tested flow rates (300-1600 μL h-1). As opposed to merely surface charges typically considered when electrospinning leaky dielectric fluids, as suggested by Melcher and Taylor (1969), our results suggest that the measured current is also affected by volumetric charges from charged PAA in the bulk of the jet. The proposed additional charge transport might affect the orientational order within PE-based nanofibers and their diameter.

Fe dopant controlled the ferromagnetic, structural, thermal, optical, and electrical characteristics of CdO nanoparticles

This research paper presents a study on (Fe) doped CdO nanoparticles focusing on their structural (XRD), thermal (TGA and DTA), optical (UV–vis), magnetic (VSM and ESR), and electrical characteristics. The synthesis of Cd1-xFexO with (x = 0.0, 0.01, 0.05, 0.10, 0.15, and 0.20) nanoparticles was carried out using the co– precipitation technique. Fe dopants showed a great impact on the structural parameters and the thermal stabilities of obtained nanomaterials. SEM and TEM imaging techniques are employed to investigate the morphology, size, and distribution of the Cd1-xFexO nanoparticles. UV spectroscopy was employed to better understand the electronic transitions and optical characteristics. Furthermore, magnetization measurements from ESR and VSM showed a weak ferromagnetic order with a high Fe concentration. For instance, the Ac electrical conductivity measurements were used to determine the electrical properties, dielectric losses, and charge transport mechanisms between the Fe-dopants and CdO. The structural, thermal, optical, magnetic, and electrical characteristics data are complemented to better understand for Cd1-xFexO materials for employing them in magnetic storage and sensors, photocatalysis, other future applications.

Dielectric relaxation and conductivity phenomena in ferroelectric ceramics at high temperatures

The issues related to microstructure and its effects on functional properties of electroceramics become increasingly prominent with the progressive downscaling of electronics. In this study, temperature-dependent dielectric and impedance data of BaTiO3 (BT), Sr-doped BT (BST) and layer-structured BaBi4Ti4O15 (BBTO) ceramics are systematically investigated to reveal the effects of doping and perovskite layering on the dielectric relaxation and conduction processes at high temperatures. By using complex impedance spectroscopy, it is demonstrated that the ceramics are electrically heterogeneous structures displaying a non-ideal Debye-like behavior at high temperatures. Using a suitable equivalent circuit model, the impedance diagrams at different temperatures are simulated and the refined values of macroscopic resistance and capacitance are used for the identification and characterization of particular microstructural regions (grains, grain boundaries, interfaces, etc.). The approach of combining the impedance, electric modulus and permittivity formalisms is demonstrated to be effective in explaining the peculiarities of the electrical charge transport mechanism and relaxation in the grains, grain boundaries and interface layers of the ceramics.

Minimum entropy production in inhomogeneous thermoelectric materials

Due to their potential applications in energy production based on waste heat, direct solar radiation or other energy sources, semiconductor materials have for years attracted the attention of theoretical and experimental researchers. The focus has been on improving the performance of thermoelectric devices through several strategies and special interest has been placed on materials with spatially inhomogeneous transport properties. Inhomogeneity can be achieved in various ways, all of them leading, to a greater or lesser extent, to an improvement of the thermoelectric performance. In this paper, general linear heat and electric charge transport processes in inhomogeneous materials are addressed. The guiding idea followed here is that there exists a relationship between inhomogeneity (structuring), minimum entropy production and performance which may be fruitfully exploited for designing more efficient thermoelectric semiconductor devices. We first show that the stationary states of such materials are minimum global entropy production states. This constitutes an extension of the validity of Prigogine’s minimum entropy principle. The heat and charge transport equations obtained within the framework of classical irreversible thermodynamics are solved to find the stationary profiles of temperature and self-consistent electric potential in a one-dimensional model of a silicon–germanium alloy subjected to an external temperature difference. This allows us to assess the effect of the spatial inhomogeneity on the thermoelectric performance. We find that, regardless of the value of the applied temperature difference, the system may efficiently operate in a regime of minimum entropy production and high efficiency.

Sulfite activation by Jahn-Teller-driven oxygen vacancies Cu-Mn composite oxide for chlortetracycline degradation

Copper-manganese composite metal oxides (CuMnOy) were prepared by hydrolysis-driven oxidation-reduction method and used to activate sulfite to degrade chlortetracycline hydrochloride (CTC) for the first time. The Jahn-Teller ions Mn3+ and Cu2+ exist in CuMnOy, which form a solid electric charge transport redox system and ensure the continuous generation of reactive oxygen species (ROS). Through the systematic study of the experimental parameters such as sulfite concentration, catalyst metal molar ratio, catalyst amounts and initial pH, the optimal degradation rate of CTC could reach 91.74% within 10 min and 94.46% after 30 min. The major reactive radicals were determined by radical quenching experiments and electron paramagnetic resonance (EPR) trapping techniques, and it was confirmed that SO4•- and •O2- played a nonnegligible role in the process of degrading CTC. Density functional theory (DFT) calculations show that higher Fukui indices (f- and f0) of CTC sites are more vulnerable to free radical attack. CuMnOy has low CTC degradation intermediate toxicity, high catalytic performance, good anti-interference ability, reusability and stability, and possesses decent application potential in the actual water treatment field.

Tailoring Interlayer Charge Transfer Dynamics in 2D Perovskites with Electroactive Spacer Molecules.

The family of hybrid organic-inorganic lead-halide perovskites are the subject of intense interest for optoelectronic applications, from light-emitting diodes to photovoltaics to X-ray detectors. Due to the inert nature of most organic molecules, the inorganic sublattice generally dominates the electronic structure and therefore the optoelectronic properties of perovskites. Here, we use optically and electronically active carbazole-based Cz-Ci molecules, where Ci indicates an alkylammonium chain and i indicates the number of CH2 units in the chain, varying from 3 to 5, as cations in the two-dimensional (2D) perovskite structure. By investigating the photophysics and charge transport characteristics of (Cz-Ci)2PbI4, we demonstrate a tunable electronic coupling between the inorganic lead-halide and organic layers. The strongest interlayer electronic coupling was found for (Cz-C3)2PbI4, where photothermal deflection spectroscopy results remarkably reveal an organic-inorganic charge transfer state. Ultrafast transient absorption spectroscopy measurements demonstrate ultrafast hole transfer from the photoexcited lead-halide layer to the Cz-Ci molecules, the efficiency of which increases by varying the chain length from i = 5 to i = 3. The charge transfer results in long-lived carriers (10-100 ns) and quenched emission, in stark contrast to the fast (sub-ns) and efficient radiative decay of bound excitons in the more conventional 2D perovskite (PEA)2PbI4, in which phenylethylammonium (PEA) acts as an inert spacer. Electrical charge transport measurements further support enhanced interlayer coupling, showing increased out-of-plane carrier mobility from i = 5 to i = 3. This study paves the way for the rational design of 2D perovskites with combined inorganic-organic electronic properties through the wide range of functionalities available in the world of organics.

Dependence of Electrical Charge Transport on the Voltage Applied across Metal–Graphene–Metal Stack under Fixed Compressing Force

While charge transport in the horizontal plane of graphene has been widely studied, there is only limited understanding about the transport across a stack of films that include graphene sheets. In this report, a model of a metal–graphene–metal stack was produced and investigated via detailed analysis of experimental dependences of electrical current on applied external voltage. Scanning probe microscopy (SPM) was used to measure the dependences of the local tunneling current on the voltage under fixed compressing force. The SPM platinum probe produced the compressing force on gold-supported graphene in the metal–graphene–metal system. The experimental results were explained by a model that included the pinning of the Fermi level of graphene to platinum and the related changes in the parameters of the potential barrier for the electron flow. It was demonstrated that low-voltage and high-voltage intervals can be identified in the charge transport across the metal–graphene–metal stack. In the high-voltage interval (approximately > |±0.7| V in the tested stack), the history of the current measurement was detected due to the charge accumulation. In the low-voltage interval, the current was determined by the electronic states near the Fermi level. In this interval, the graphene layer can function as a blocking gate for the electron transport in the metal–graphene–metal system.