Conduction Mechanism Research Articles

Phase Separation‐Induced Electrical Conductivity for Liquid Metal‐Embedded Plastic Hybrid Composites with Metallic Conductivity and Recyclability

AbstractConductive fillers‐embedded plastic polymer hybrid composites are crucial electronic materials in modern technologies owing to their tunable conductive properties, low density, and corrosion resistance. However, the application of traditional rigid inorganic conductive fillers‐embedded plastic composites is constrained by their subpar electrical conductivity and mechanical properties. Consequently, liquid metals (LMs) including gallium and gallium‐based alloys, have recently emerged as the preferred conductive flexible fillers over traditional rigid fillers. This work employs a solvent evaporation method and phase separation‐induced conductivity mechanism. The resulting flexible and electrically conductive LM‐polycarbonate (PC) film circuits demonstrate ultrahigh metallic conductivity, robust mechanical performance, excellent solvent recyclability, and notable processability. The fluidic nature of LMs and the superior mechanical properties of the PC polymer confer high electrical stability and durability to the LM‐PC film circuits under diverse mechanical forces and environmental conditions. The LM‐PC film circuits are exceedingly promising and apt for use as flexible conductors in contemporary electrical applications, including electricity transmission and underwater working.

Synergistic Effect of Aluminum Nitride and Carbon Nanotube-Reinforced Silicon Rubber Nanocomposites.

Constructing a synergistic effect with different structural fillers is an important strategy for improving the comprehensive properties of polymeric composites. To improve the comprehensive properties of two-component additive liquid silicon rubber (SR) materials used in electronics packaging, the synergistic effect of granular aluminum nitride (AlN) and tubular carbon nanotube (CNT)-reinforced SR nanocomposites was investigated. AlN/CNT/SR composites with different AlN/CNT ratios were fabricated with two-component additive liquid SR via the thermal curing technique, and the influence of AlN/CNT hybrid fillers on the hardness, strength, elongation at break, surface resistivity, thermal conductivity, and thermal decomposition was investigated in detail. With the incorporation of AlN/CNT hybrid fillers, the comprehensive properties of the obtained AlN/CNT/SR composites are better than those of the AlN/SR and CNT/SR composites. The synergistic thermal conductive mechanism of AlN/CNT hybrid fillers was proposed and demonstrated with the fractural surface morphology of the obtained composites. The obtained AlN/CNT/SR composites show promising applications in electronic packaging, where necessary mechanical strength, electrical insulating, thermal conductivity, and thermal stable materials are needed.

Rietveld refinement and complex dielectric, modulus and impedance study of Ni0.27Cu0.10Zn0.63AlxFe2-xO4 bulk ceramics

The structural, electrical, and magnetic characteristics of NiCuZn bulk ceramics under the influence of trivalent Al with step size 0.02 have been prepared through the sol–gel synthesis method. Single-phase cubic spinel structure was confirmed from the XRD patterns which were also verified through Rietveld refinement analysis with lattice constant between 8.406 Ǻ to 8.416 Ǻ. The output was used to determine the cation distributions between A-sites and B-sites which revealed the B-site preferences of Al. The SEM micrographs showed the distribution of grain and grain boundary as ferrite particles. The law of approach to saturation technique was used to obtain hysteresis parameters which provided saturation magnetization in the range of 44 emu/g to 57 emu/g. Dielectric parameters were obtained by implementing an impedance analyzer and the dielectric constant was fitted theoretically for determining its nature. Electric modulus spectrum was also analyzed for the conduction mechanism of the prepared compounds. Impedance spectroscopy was used for finding electrical properties and Cole-Cole analysis provided the values of Rg and Rgb.

Study of direct current charge transport mechanism in a series of iridium metal complexes based on varying ancillary and cyclometalated ligands

The mechanism of charge transport in a series of iridium metal complexes prepared with varying ancillary and cyclometalated ligands is reported here. The structural conformation of the synthesized complexes is acquired via NMR spectroscopy and elemental analysis. The photophysical properties of the samples are investigated through UV–visible and photoluminescence spectroscopy. The investigation of the temperature-dependent dc electrical conductivity of the samples is conducted within the temperature range of 280–473 K. The room temperature conductivity of all samples is determined to be of the order ∼10−8 S/cm. All the complexes exhibit semiconducting behavior in a certain temperature range above room temperature. A continued elevation in temperature leads to reduction in the conductivity of all the samples resulting in metal-like conduction behavior above a certain temperature. The transition temperature of the iridium metal complexes is attributed to the removal of the coordinated water molecule from the samples as suggested by thermal analysis of the complexes. The removal of water molecule from the sample is expected to localize the electron densities which consequently results in a fall of the conductivity in the samples. The conduction mechanism in the samples is analyzed in the light of band conduction mechanism and Mott’s variable range hopping model. All the samples are found to obey 1-D VRH mechanism. The activation energy and the corresponding Mott’s parameters are derived from the ln σ vs 1/T curves.

Multi-layers hexagonal hole MXene trap constructed by carbon vacancy defect regulation strategy enables high energy density potassium-ions storage

Due to the slow reaction kinetics of potassium-ions with large size radius in layered materials, the energy density of aqueous potassium-ion hybrid supercapacitors (PIHCs) is severely limited. At the same time, the treatment of defects is a “double-edged sword” in energy storage materials, which requires targeted and precise regulation. In order to solve this problem, multi-layers hexagonal hole MXene trap was constructed by using the carbon vacancy defect regulation strategy, and high specific capacitance and energy density potassium-ion storage was realised in PIHCs. The structure-activity relationship at the atomic level was elucidated in combination with the pseudo-capacitance effect caused by the change of valency of newly exposed titanium atoms in the inner wall of the hexagonal hole MXene trap. By density functional theory, the adsorption energy and kinetic analysis of multi-layers hexagonal hole MXene for potassium-ions were calculated, and the optimal position and quantity of potassium-ions were determined. By quantitative analysis of electron band structure and differential charge density, the internal mechanism of high conductivity and energy density of multi-layers hexagonal hole MXene PIHCs was revealed.

Evaluation of mobility range of charge carriers at microwave region in Cr substituted [formula omitted]-CdFe2O4 ferrites

A series of chromium-substituted cadmium post-spinel ferrites CdCrxFe2-xO4 (x = 0.0, 0.1, 0.3, 0.5) have been synthesized through the sol-gel auto-ignition method. The structural, vibrational, dielectric, magnetic, and microwave absorption properties of β-spinel ferrites through modern techniques which include X-ray diffraction, FTIR Spectroscopy, and Vector network analyzer. X-ray diffraction technique was used for structural investigation which confirmed the monophasic orthorhombic structure of prepared samples and a detailed study revealed that no impurity/additional phases were detected. Crystallite size and strain were extracted via the Williamson-Hall (W–H) method and Size strain plot (SSP). Vibrational spectroscopy (FTIR) successfully verified the spectral qualities of studied ferrites as measured wave number ranges between 400 and 600 cm−1. X-ray photoelectron spectroscopy verified that all metal ions exist and possess the corresponding electronic states. Electrical properties have been investigated at the microwave region (1 MHz – 6 GHz). The conduction mechanism has been studied via Johnscher power law. The Cole-Cole plot of all the samples consisting of two semicircles corresponding to grain and grain boundaries described the increasing conduction phenomena. In the present research, stable dielectric constant, dielectric loss, enhanced magnetic characteristics, and minimum reflection loss (−31.9 dB) make these CdCrxFe2-xO4 nano-crystallites most suitable candidates for highly dense and high-frequency microwave devices for EMI shielding material.

Study of dielectric and interfacial properties of functional biopolymer-based electrolyte with enhanced conductivity for energy storage application

This study investigates sodium (Na+) ion-conductive biopolymer blend electrolytes with glycerol as a plasticizer for energy storage. Through FTIR, impedance spectroscopy, transference number measurement (TNM), and linear sweep voltammetry (LSV), we identify an optimal film for electric double layer capacitor (EDLC) application. Glycerol induces notable changes in polymer-salt interaction, evidenced by FTIR band shifts reflecting increased free ions. Impedance measurements show reduced bulk resistance with optimal plasticizer content, emphasizing the system's suitability for energy storage. The system exhibits high real permittivity relative to imaginary at lower frequencies, attributing to glycerol's dielectric constant and small bulk resistance. Loss tangent (tanδ) and Argand plots reveal the dominant ion conduction mechanism. Electrochemical assessments support the suitability of the film for EDLC applications, featuring a favorable transference number (tion = 0.94) and high decomposition voltage (2.6V). Cyclic voltammetry (CV) curves demonstrate effective EDLC device design with significant capacitance adaptability across varying scan rates (5.946 F/g to 24.074 F/g).

Design of gelatin-based bionic device for neural computing applications

This study introduces an approach to the development of resistive random-access memory (RRAM) devices by utilizing gelatin-based materials and incorporating an ultrathin Al2O3 interface layer fabricated using atomic layer deposition (ALD). The integration of the ALD technology for Al2O3 deposition ensures precise control over the layer thickness and quality, contributing to enhanced device uniformity and stability. The AGAI device can withstand more than 200 switching cycles while maintaining a high ON/OFF ratio exceeding 103, and it also successfully emulates synaptic plasticity characteristics, including long-term synaptic plasticity and short-term synaptic plasticity, as demonstrated by their responses to paired-pulse facilitation and paired-pulse depression, respectively, thereby validating their potential for neural computing applications. Additionally, the hybrid conduction mechanism in the AGAI device, involving aluminum and oxygen vacancy filaments, provides remarkable control over the switching process, leading to repeatability in synaptic characteristics and resistance states. These capabilities introduce new possibilities for the development of neuromorphic computing systems, which aim to mimic the functionality of the human brain in processing and storing information.

Dual doped fluorite oxide enabling enhanced performance for low-temperature ceramic fuel cells

Ceria-based electrolyte materials are of great interest for solid oxide fuel cell applications because they exhibit low ohmic resistance and high ionic conductivity, especially at a low temperature of 550oC. Consequently, we have designed a very interesting electrolyte Al and Nd dual-doped SDC (Sm0.1Ce0.9O2) using the sol–gel technique to function as an electrolyte for LT–CFCs (low-temperature ceramic fuel cells). The AN–SDC (Al0.15N0.15-Sm0.1Ce0.6O2) as an electrolyte shows a maximum power output of 1085 mW/cm2 with a high ionic conductivity of 0.22 S/cm at 550oC. This high performance is mainly because of the co-doping into SDC, which facilitates many oxygen vacancies, enabling faster stabilized ion transportation through the AN–SDC lattice. The low resistance of either the ohmic and grain boundary resistance + the microstructure features of AN–SDC contribute to achieving higher fuel cell performance. In addition, dual doping into SDC might build a synergistic effect, which further improves devices’ performance. The ionic conduction mechanism has been explained based on the dual doping of the incorporation of Al and Nd into the SDC. Dual doping is a promising, feasible avenue for designing electrolytes to enhance the performance of LT–CFC devices.

Alternative processing routes on CsH2PO4 proton conductors: Cold sintering and ball-milling routes

Cesium dihydrogen phosphate (CsH2PO4) holds great potential as electrolyte for intermediate-temperature fuel cells and electrochemical devices due to its high proton conductivity (≥10−2 S/cm). This study reports on the variation of the microstructure of CsH2PO4 and its effect on its electrical and thermal properties, with special attention to the low-temperature conductivity behavior. To manipulate morphology, the particle size was decreased by wet ball-milling, while variations in grain growth were achieved by cold sintering. Above the superprotonic phase transition, the electrical conductivity was effectively independent of the grain size. Nonetheless, at lower temperatures, a brick layer analysis on the impedance data revealed that the conductivity of the monoclinic phase is governed by the conduction pathways along the parallel grain boundaries due to the humidified atmosphere. Overall, we propose two conduction mechanisms that could explain the grain boundary conductivity of these samples, revealing critical links between sample morphology and low-temperature electrical behavior.

Mechanisms of the Accelerated Li+ Conduction in MOF-Based Solid-State Polymer Electrolytes for All-Solid-State Lithium Metal Batteries.

Solid polymer electrolytes (SPEs) for lithium metal batteries have garnered considerable interests owing to their low cost, flexibility, lightweight, and favorable interfacial compatibility with battery electrodes. Their soft mechanical nature compared to solid inorganic electrolytes give them a large advantage to be used in low pressure solid-state lithium metal batteries, which can avoid the cost and weight of the pressure cages. However, the application of SPEs is hindered by their relatively low ionic conductivity. In addressing this limitation, enormous efforts are devoted to the experimental investigation and theoretical calculations/simulation of new polymer classes. Recently, metal-organic frameworks (MOFs) have been shown to be effective in enhancing ion transport in SPEs. However, the mechanisms in enhancing Li+ conductivity have rarely been systematically and comprehensively analyzed. Therefore, this review provides an in-depth summary of the mechanisms of MOF-enhanced Li+ transport in MOF-based solid polymer electrolytes (MSPEs) in terms of polymer, MOF, MOF/polymer interface, and solid electrolyte interface aspects, respectively. Moreover, the understanding of Li+ conduction mechanisms through employing advanced characterization tools, theoretical calculations, and simulations are also reviewed in this review. Finally, the main challenges in developing MSPEs are deeply analyzed and the corresponding future research directions are also proposed.

Charge carrier motion and Mn-spin coupling defining the transport behaviors and the magnetic order at DySrCaMnO3 polycrystalline ceramic

The Ca-doped Dy0.5Sr0.5MnO3 manganite was synthesized using the Sol-Gel technique. The material demonstrates semiconducting behavior across a wide range of temperatures. This behavior could be attributed to the involvement of small polaron hopping, Shklovskii-Efros variable range hopping, and Mott-variable range hopping mechanisms. The Shimakawa Model is used in the intermediate temperature range to verify the existence of multiphonons in the compound. The conductance spectra adhere to the Jonscher power law and can be elucidated by the utilization of the Jump relaxation model. The manganite structure deviated from Summerfield scaling, indicating that numerous crystalline-ordered materials possess unexplored conduction and relaxation mechanisms, unlike amorphous systems. Magnetic anomalies at around 6K were observed, indicating antiferromagnetic (AFM) interactions between Dy–Dy pairs. Another anomaly occurs at approximately 40K, indicating AFM coupling between Mn-spins.

Optimizing electromechanical properties of KNN-based piezoelectric ceramics through regulation of lattice distortion

With the rapid development of broadband transducers, there is an increasing demand for enhanced electromechanical properties in lead-free piezoelectric ceramics. In this study, the strategies to enhance the electrical properties of ceramics were explored by doping BaZrO3 into 0.96(K0.48Na0.52)Nb0.96Sb0.04O3-0.04(Bi0.5Ag0.5)ZrO3 ceramics, inducing lattice distortion (c/a) and regulating the phase structure. The ceramics doped with 1.5 mol% BaZrO3 demonstrate excellent electrical performance, with a piezoelectric coefficient (d33) of 545 pC/N, a relative dielectric constant (εr) of 4126, and an electromechanical coupling factor (kp) of 54.1 %. The reduced c/a ratio and rhombohedral-orthorhombic-tetragonal phase structure reduce the polarization energy barrier and promote the ordered arrangement of ferroelectric dipoles, thereby enhancing the comprehensive performance of the ceramics. Lastly, the electrical impedance of ceramics is studied in detail and reveals the main conduction mechanism in the microscopic region. This research provides new insights into optimizing the electrical properties of ceramics through microstructural manipulation and demonstrates the potential application of KNN-based ceramics in high performance piezoelectric transducers.

Unveiling the Structure and Diffusion Kinetics at the Composite Electrolyte Interface in Solid‐State Batteries

AbstractThe “interface” between polymer and oxide within the polymer‐oxide composite electrolytes is widely acknowledged as a crucial factor influencing ionic conduction. However, a fundamental understanding of the precise composition and/or micro‐structure, and the ionic conduction mechanism at the complex interface has remained elusive, primarily due to a dearth of compelling experimental evidence. In this study, the intricate correlation between morphology and composition in composite electrolytes is discerned by leveraging advanced 1D and 2D exchange nuclear magnetic resonance spectroscopy (1D and 2D EXSY NMR) techniques. Notably, this research represents the inaugural elucidation of the microstructure of the interface. The findings underscore the pivotal role of the preparation conditions for polymer‐oxide composite electrolytes, particularly the solvent selection, in determining the formation of the interface structure. Direct insights into the lithium‐deficient surface of Li6.4La3Zr1.4Ta0.6O12 (LLZTO) are provided and elucidate the timescales of Li‐ion exchange processes among various components. Furthermore, a comprehensive investigation into the roles of individual components within the composite electrolyte on the Li‐ion conduction mechanism is conducted through the 6Li→7Li isotope tracer technique as a function of current density.

Examining the Desirable Properties of ZnSnO y by Annealing Treatment with a Real-Time Observation of Resistivity.

In this report, 38 nm-thick amorphous zinc-tin oxide (a-ZTO) films were deposited by radio frequency magnetron cosputtering. a-ZTO films were annealed by in situ monitoring of the sheet resistance improvements during the annealing process. A sharp drop in the slope of the sheet resistance curve was observed. The activation energies for the sheet resistance slope were calculated. The activation energy of the reaction for a sharp drop in the slope is much higher than the activation energy for the rest of the slope. Based on the activation energy values, six annealing temperatures were selected to saturate the highest conductivity at lower annealing temperatures and to identify the effects associated with annealing time. We found a direct correlation between annealing temperatures and the duration of the annealing treatment. a-ZTO films with a high conductivity of 320 S/cm were achieved by annealing at a temperature of 220 °C. It is noteworthy that the annealing temperature of 220 °C has clearly replaced the temperature of 300 °C. An irreversible decrease in resistivity was observed for all films. The conduction mechanism of films before and after annealing was determined. We confirm that all films individually exhibit semiconducting and metallic behaviors in the conduction mechanism before and after the lowest resistivity saturation.

Understanding Compartmentation Failure for High-Rise Timber Buildings

The traditional concept of compartmentation guaranteed by fire resistance is mainly concerned with the problem of destructive internal spread potential. External convective spread potential pertains to the loss of compartmentation associated with windows and facade systems. As such, it is assumed that internal fire spread occurs following mechanisms of excessive heat conduction and/or successive failure of the compartment boundaries, which can be, in most cases, conservatively characterised using traditional methods of performance assessment such as fire resistance. Nevertheless, external fire spread represents a potentially more effective route by which fire can spread through the convective advancement of flames and hot gases. This is particularly important in cases such as timber construction, where the presence of exposed timber can result in increased convective spread potential and where loss of compartmentation can result in disproportionate consequences. A simplified compartment fire model is proposed with the objective of quantifying the fuel contribution of exposed timber elements to the compartment fire and determining the impact of variable percentages of exposed timber on the convective spread potential. The overall results show that the convective fire spread potential increases with the increasing percentage of available timber.

Ultrathin and Smooth Pheomelanin-like Photoconductive Film.

This study introduces a facile method for the substrate-independent deposition of pheomelanin-like films, revealing unique and promising electrical characteristics. The conventional darkening of a dopamine solution at a basic pH was significantly delayed by the addition of l-cysteine, resulting in a distinctive temporal pattern: an initial quiescent period without apparent color change followed by an abrupt and explosive burst. Surprisingly, within the quiescent period, the deposition of ultrathin and smooth pheomelanin-like films was observed, in addition to rough and thick films formed after the burst. Regardless of thickness or texture, these films exhibited common chemical properties, including moisture-capturing capability and dark- and bright-state conductivities. Particularly noteworthy were consistent photocurrent responses under bias voltage across various pheomelanin-like films, which were not observed in polydopamine films, highlighting the influential role of l-cysteine addition. These findings present a novel avenue for the potential application of pheomelanin-like films in bioelectronics, emphasizing their distinct electrical characteristics and prompting further exploration into their intricate conductive mechanisms. The study contributes to advancing our understanding of melanin-based materials and their potential in diverse scientific and technological domains.

(1-x)Ni0.9Mn2.1O4-xLaCr0.6Mn0.4O3 composite ceramic with controllable electrical properties for low resistance NTC thermistors

A series of NTC composite ceramics based on (1-x)Ni0.9Mn2.1O4-xLaCr0.6Mn0.4O3 (x = 0.2, 0.25, 0.3, 0.4, and 0.5) were prepared by the solid-state method. The composite ceramics are mainly composed of the orthogonal perovskite phase and the cubic spinel phase. The Ni ions are diffused into the perovskite phase, La and Cr ions are diffused into the spinel phase. The interdiffusion of ions in two phases leads to the structural change of the two phases in the composite ceramics. The conduction mechanism of composite ceramics is the coexistence of electron jumping and double exchange conduction. The resistivity ρ25 and B values vary in the range of 17.4–1056 Ω cm and 2140–3600 K, respectively. Indicating that the electrical properties can be adjusted arbitrarily. In addition, increasing the content of perovskite can improve the stability of the material. The prepared NTC composite ceramic has good electrical properties and stability, so it has good application potential in the field of low resistance.

Electrical analysis and molecular dynamics of anion in ferroelastic [(CH3)4P]2CoBr4 crystal near high-temperature phase transitions

The recent technological advances require an aligned innovation in the materials used for the construction of electronic devices. Hybrid materials play a important role in the optoelectronic applications because they combine both the organic and inorganic components. To this end, the [(CH3)4P]2CoBr4 compound was successfully synthesized using the slow evaporation solution growth approach at room temperature. In-depth research has been conducted on the structural, morphological, vibrationnal and electrical characteristics. The [(CH3)4P]2CoBr4 compound crystallises in the monclinic system with P121/C1 space group. The examination of SEM images reveals that the majority of grains have an average size of around 4 μm with irregularly shaped and non-spherical particles. The measured Raman spectra demonstrate the coexistence of two transition phases located at 373 K and 428 K. In fact, these observations suggest that the anionic components play a significant role in influencing the phase transitions mechanism. Analysis of the complex impedance spectra reveals that the electrical characteristics of the material is strongly dependent on both frequency and temperature. That indicates the existence of a relaxation phenomenon and of a semiconductor-type behavior. One single semicircle is detectable in the Nyquist plots of the complex impedance spectra, which can be satisfactorily fitted with a combination of R//C//CPE elements assigned to the bulk response. Therefore, we can conclude from this behavior that the sample is electrically homogeneous. The dependency of s(T) on temperature also shows that the correlated barrier hopping and the non-overlapping small polar on tunneling model are the responsible mechanisms for the AC conduction in [(CH3)4P]2CoBr4.

High H2O-Assisted Proton Conduction in One Highly Stable Sr(II)-Organic Framework Constructed by Tetrazole-Based Imidazole Dicarboxylic Acid.

Solid electrolyte materials with high structural stability and excellent proton conductivity (σ) have long been a popular and challenging research topic in the fuel cell field. This problem can be addressed because of the crystalline metal-organic frameworks' (MOFs') high structural stability, adjustable framework composition, and dense H-bonded networks. Herein, one highly stable Sr(II) MOF, {[Sr(H2tmidc)2(H2O)3]·4H2O}n (1) (H3tmidc = 2-(1H-tetrazolium-1-methylene)-1H-imidazole-4,5-dicarboxylic acid) was successfully fabricated, which was structurally characterized by single-crystal X-ray diffraction and electrochemically examined by the AC impedance determination. The results demonstrated that the σ of the compound manifested a positive dependence on temperature and humidity, and the optimal proton conductivity is as high as 1.22 × 10-2 S/cm under 100 °C and 98% relative humidity, which is at the forefront of reported MOFs with ultrahigh σ. The analysis of the proton conduction mechanism reveals that numerous tetrazolium groups, carboxyl groups, coordination, and crystallization water molecules in the framework are responsible for the high efficiency of proton transport. This work offers a fresh perspective on how to create novel crystalline proton conductive materials.