Electrical Conductivity Coefficient Research Articles

Dynamics of changes in the temperature coefficient of electrical conductivity of distilled water in conductometric cells during heating and cooling

Dynamics of changes in the temperature coefficient of electrical conductivity of distilled water in conductometric cells during heating and cooling

Roles of nonlocal electron-phonon coupling on the electrical conductivity and Seebeck coefficient: A time-dependent DMRG study

Roles of nonlocal electron-phonon coupling on the electrical conductivity and Seebeck coefficient: A time-dependent DMRG study

Study of optoelectronic, transport, and mechanical aspects of lead-free double perovskites Rb2AgTlX6 (X = Cl, Br) for green energy applications

The double perovskites are emerging candidates for renewable energy applications. This work uses the extensive density functional theory (DFT) method to investigate the structural, optoelectronic, transport, and mechanical properties of Rb2AgTlX6 (X = Cl, Br). The thermal and structural stabilities of Rb2AgTlX6 (X = Cl, Br) are investigated through formation energy and tolerance factorevaluation.The Rb2AgTlCl6 and Rb2AgTlBr6 have direct band gaps of 1.61 eV and 1.08 eV. The reported band gap reduction is associated with the p-d hybridization of cations and anions. Investigating optical characteristics yields important insights via the dielectric constant ε(ω), refractive index n(ω), absorption α(ω), and reflectivity R(ω). The ability to absorb light in visible and ultraviolet spectra as demonstrated by optical characteristics highlights the potentialof Rb2AgTlX6 for solar cell technology. In addition, the significant electrical conductivity and Seebeck coefficient led to a notable reduction in heat conductivity and figure of merit values of 0.68 and 0.67 at higher temperatures. Elastic parameters, Pugh’s, and Passion’s ratios are studied to confirm materials’ mechanical stability and nature. The studied materials have been found mechanically stable and brittle. Together, our findings demonstrate the distinctive and intriguing features of Rb2AgTlX6 (X = Cl, Br) are suitable for cost-effective energy conversion applications.

Fermi energy modulation by tellurium doping of thermoelectric copper(I) iodide

Copper(I) iodide (CuI) is the leading inorganic p-type transparent conductor, attracting major attention for its promising optoelectronic properties and facile growth methods, although, commercial uptake is limited due to its as-of-yet insufficient electrical conductivity. Doping CuI with the chalcogens (O, S, Se, Te) is a viable route to tune its electrical conductivity for applications such as in thin film transistors, hole transport layers in solar cells, and transparent thermoelectric generators. The heaviest chalcogen element, Te, is yet to be explored in heavily intrinsically p-type doped CuI at non-alloying concentrations, the subject of the present work. We report the effects of tellurium at the boundary between the doping and alloying regime (up to a maximum of 2.4 % Te) in CuI thin films and investigation the variation in the thermoelectric properties and electronic band structure of the material. Ion implanting tellurium into CuI led to a progressive reduction in the films' work functions from 4.9 eV to 4.5 eV while the ionization potential remained unchanged, measured through photoemission spectrometry. This signified a modulation of the Fermi energy relative to the valence band edge, having a major effect on the materials' electrical conductivity and Seebeck coefficient, the former decreasing by 3 orders of magnitude, while the latter increased by 80 %. We conducted density functional theory (DFT) calculations to elucidate the effect of tellurium doping on the band structure of CuI. Tellurium doping corroborated the shift of Fermi energy, the incorporation of impurity acceptor states deeper into the band gap, in addition to disordering the valence band maximum. This work shows that, the Fermi energy in heavily p-type doped CuI can be moved away from the valence band through Te doping in addition to introducing band disorder, useful for controlling the hosts’ transport properties.

Powder aerosol deposited calcium cobaltite as textured P-type thermoelectric material with power factors approaching single crystal values

In this work, the thermoelectric material calcium cobaltite Ca3Co4O9 (CCO), a promising p-type conducting thermoelectric oxide with anisotropic properties, was processed by the powder aerosol deposition method (PAD) to form a dense ceramic CCO film with a thickness in the µm range. The prepared films were characterized regarding their microstructure and thermoelectric properties between room temperature and 900 °C. After heat treatment at 900 °C, the CCO PAD film in-plane shows excellent properties in terms of electrical conductivity (280 S/cm at 900 °C) and Seebeck coefficient (220 µV/K at 900 °C). The calculated power factor in-plane (ab) reaches with 1125 µW/(m K2) 40 % of the single crystal value, surpassing the known-properties of CCO bulk ceramics. Examination of the microstructure shows a strong fiber texture of the film as well as a strong coarsening of the grains during the first heat treatment up to 900 °C.

Wedge-shape Al and Mg co-doped zinc oxide thin films: A Facile Route to achieve high thermoelectric power factor

Thin film thermoelectric technology has immense potential to become a next-generation power source for small-scale electronics. However, the rapid development of thin film thermoelectric still lacks a controllable structural design to improve the performance of thermoelectric devices for required temperature applications. This work presented a controlled thermoelectric design of ZnO-based thin films by Al and Mg co-doping using ALD. Herein, the Mg-doped ZnO sample exhibits the highest Seebeck coefficient of −311.83 μVK−1 at 500oC, while the maximum thermoelectric power factor of 3.68 μWcm−1K−2 is obtained at 300oC, which drops for higher temperatures. This decrease in power factor resulted from the reduction in electrical conductivity above 300oC. Similarly, the Al and Mg co-doped ZnO sample (Mg/Al ≈2 at%) exhibits a high thermoelectric power factor of 3.85 μWcm−1K−2 for ZnO based material due to its moderate electrical conductivity and Seebeck coefficient value at 325oC and behave monotonically for elevated temperatures. Scanning electron microscope (SEM) images show the formation of wedge-shaped structures for Al-incorporated samples, which helps to boost the overall thermoelectric performance. Additionally, we performed XRD, UV–Vis, Hall, and AFM analysis to get a deep insight into structural, optical, electrical, and surface features of the grown thin films and their linkage with the thermoelectric properties.

Understanding the electronic structure and transport properties of A-site SrTiO3-δ ceramics with enhanced configuration entropy

Since SrTiO3 is attractive due to its versatile electronic properties ranging from dielectric to semiconducting behavior, the effect of systematic co-substitution of various A-site cations on the electronic structure and transport properties of oxygen-deficient SrTiO3-δ bulk ceramics was analyzed. The materials were synthesized by reverse co-precipitation method and densified by spark plasma sintering (SPS) in a vacuum, followed by a post-thermal treatment in a reducing atmosphere (5% H2/Ar). The phase purity was confirmed by X-ray diffraction (XRD), different microstructures were revealed by scanning electron microscopy (SEM), and characterization in terms of electrical conductivity (σel) and Seebeck coefficient (S) were performed. The largest power factor was obtained with Sr0.25Ca0.25Na0.25La0.25TiO3-δ by maintaining electrical conductivity while increasing the Seebeck coefficient. Density Functional Theory (DFT) calculations were applied to obtain information on band structures, the projected density of states (PDOS), and electron density differences (EDD). Band structures indicated that oxygen deficiency essentially changed the conductive nature of the studied materials by shifting the Fermi level to the conductive zone, while PDOS plots define the role of each element located at the A site. The electronic structure is affected to the greatest extent in the cases when Nd and Pr are present at the A-site. However, the obtained experimental and computational (DFT) results could not completely match and explain all phenomena since understanding the effect of different cations at A-site on oxygen vacancy formation seems to be a challenging task, and therefore, some hypotheses are proposed. This work attempts to understand the role of a particular cation at A-site on the electronic band structure and its relevance to the formation of oxygen vacancies, thereby providing valuable insights for future high-entropy perovskite titanates with improved transport properties.

Enhanced n-Type Thermoelectric Properties and Structure Evolution of Carbonized Metal-Coordination Polydopamine.

Carbonized polydopamine (cPDA) exhibits a nitrogenous graphite-like structure with n-type semiconductor property. However, the low electrical conductivity and Seebeck coefficient of cPDA cannot meet the needs of flexible thermoelectric devices. In this study, a series of metal ions were coordinated with cPDA to enhance n-type thermoelectric properties. At 300 K, all metal-coordination cPDA (metal-cPDA) samples obtain lower thermal conductivity compared to cPDA. Mn-cPDA exhibits the greatest Seebeck coefficient of -25.94 μV K-1, which is almost six times higher than cPDA. Fe-cPDA shows the best electrical conductivity of 2.45 × 105 S m-1. An optimal power factor (PF) value of 11.93 μW m-1 K-2 is achieved in Ca-cPDA with the enhanced electrical conductivity of 9.5 × 104 S m-1 and Seebeck coefficient of -11.24 μV K-1. Using Fourier transform infrared spectroscopy (FTIR), energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, X-ray diffraction (XRD), and transmission electron microscopy (TEM), we revealed the structural characterization of metal-cPDA. Our results indictate that the different metal ions (Mn2+, Zn2+, Mg2+, Al3+, Ca2+, and Fe3+) exert varying influences on the growth of graphite-like structure within metal-cPDA, which lead to the evolution of electrical conductivity. We observe that the carrier density and carrier mobility depend on both the degree of graphitization and the metal-ion coordination, which work together on electrical conductivity and Seebeck coefficient. These findings and understanding of the thermoelectric properties of PDA-based materials will help to realize high-performance n-type thermoelectric materials for flexible electronic device applications.

Order-N calculations for thermoelectric power factor based on linear response theory

We present an order-N quantum transport calculation methodology to evaluate thermoelectric transport coefficients, such as electric conductivity and Seebeck coefficient. Different from a conventional method using the electric conductivity spectrum, it obtains the coefficients directly from the correlation function between heat and electric current based on linear response theory. As an example, we apply the methodology to a two-dimensional square-lattice model with static disorder and confirm that the calculated results are consistent with those obtained by the conventional method. The proposed methodology provides an effective approach to evaluate the thermoelectric performance of micron-scale materials based on quantum mechanics from an atomistic viewpoint.

Strong anisotropic transport properties of quasi-one-dimensional ZrTe3 nanoribbons

Transition metal trichalcogenides (TMTCs) with quasi-one-dimensional (quasi-1D) structures have attracted extensive interest in diverse fields because of their unique electronic properties. Herein, we report strong in-plane anisotropic transport properties of ZrTe3 nanoribbons, which originate from their quasi-1D structures. ZrTe3 nanoribbons were mechanically exfoliated from bulk single crystals, and transport properties, including electrical conductivity (σ) and Seebeck coefficient (S), were measured in the longitudinal and transverse directions of the rectangular nanoribbons. σ was higher in the transverse direction than that in the longitudinal direction. S measurement revealed further clear anisotropic characteristics, and positive and negative S values were obtained in the longitudinal and transverse directions, respectively. Furthermore, a significant change in the transport properties was observed with a post treatment, and the potential of ZrTe3 for transport property modulation was confirmed. We believe that our findings will contribute to the understanding of anisotropic transport in quasi-1D ZrTe3 and expansion of the application fields of quasi-1D ZrTe3.

Divacancy and resonance level enables high thermoelectric performance in n-type SnSe polycrystals

N-type polycrystalline SnSe is considered as a highly promising candidates for thermoelectric applications due to facile processing, machinability, and scalability. However, existing efforts do not enable a peak ZT value exceeding 2.0 in n-type polycrystalline SnSe. Here, we realized a significant ZT enhancement by leveraging the synergistic effects of divacancy defect and introducing resonance level into the conduction band. The resonance level and increased density of states resulting from tungsten boost the Seebeck coefficient. The combination of the enhanced electrical conductivity (achieved by increasing carrier concentration through WCl6 doping and Se vacancies) and large Seebeck coefficient lead to a high power factor. Microstructural analyses reveal that the co-existence of divacancy defects (Se vacancies and Sn vacancies) and endotaxial W- and Cl-rich nanoprecipitates scatter phonons effectively, resulting in ultralow lattice conductivity. Ultimately, a record-high peak ZT of 2.2 at 773 K is achieved in n-type SnSe0.92 + 0.03WCl6.

Optoelectronic and transport properties of Lead-Free halide based Na2AgTlZ6 (Z = Cl, Br, I) double perovskites for energy harvesting applications

The bandgap engineering and deliberate band edge manipulation of perovskites make them potential candidates for the photovoltaic industry. Here we theoretically investigate the structure, density of states, and photovoltaic and thermoelectric characteristics of Na2AgTlZ6 (Z = Cl, Br, I) using WIEN2k code. The incorporation of Br and I at the Cl site caused the increase in lattice constant which leads to the decrease in bulk modulus and Debye temperature. The computed values of Poisson (<0.26) and Pugh (<1.75) ratio verified their brittle nature. The bandgap analysis reveals direct bandgap nature and bandgap value lie in the visible region for parent composition and infrared and far infrared when Cl is replaced with Br and I. The density of state plots uncovers the shifting of energy states in valence and conduction bands towards the Fermi level with the increasing number of electrons in the halogens. The increase in the value of dielectric constant, refractive index, and shifting of peaks towards lower energy value is witnessed with atomic number of halogen atoms. The viability of these compositions for thermoelectric devices is further confirmed when electrical conductivity and Seebeck coefficient dependent Figure of merit and power factor are evaluated in the temperature range of 200–800 K. In addition, the anisotropic nature of studied compositions is explored through the computation of the modulus of elasticity including Young’s modulus, Shear modulus in addition to compressibility, and Poisson’s ratio.

High‐Performance Thermoelectric Fibers from Metal‐Backboned Polymers for Body‐Temperature Wearable Power Devices

AbstractMetal‐backboned polymers (MBPs), with a unique backbone consisting of bonded metal atoms, are promising for optic, electric, magnetic, and thermoelectric fields. However, the application of MBP remains relatively understudied. Here, we develop a shear‐induced orientation method to construct a flexible nickel‐backboned polymer/carbon nanotube (NBP/CNT) thermoelectric composite fiber. It demonstrated a power factor of 719.48 μW ⋅m−1 K−2, which is ca. 3.5 times as high as the bare CNT fiber. Remarkably, with the regulation of carrier mobility and carrier concentration of NBP, the composite fiber further showed simultaneous increases in electrical conductivity and Seebeck coefficient in comparison to the bare CNT fiber. The NBP/CNT fiber can be integrated into fabrics to harvest thermal energy of human body to generate an output voltage of 3.09 mV at a temperature difference of 8 K. This research opens a new avenue for the development of MBPs in power supply.

High-Performance Thermoelectric Fibers from Metal-Backboned Polymers for Body-Temperature Wearable Power Devices.

Metal-backboned polymers (MBPs), with a unique backbone consisting of bonded metal atoms, are promising for optic, electric, magnetic, and thermoelectric fields. However, the application of MBP remains relatively understudied. Here, we develop a shear-induced orientation method to construct a flexible nickel-backboned polymer/carbon nanotube (NBP/CNT) thermoelectric composite fiber. It demonstrated a power factor of 719.48 μW ⋅m-1 K-2, which is ca. 3.5 times as high as the bare CNT fiber. Remarkably, with the regulation of carrier mobility and carrier concentration of NBP, the composite fiber further showed simultaneous increases in electrical conductivity and Seebeck coefficient in comparison to the bare CNT fiber. The NBP/CNT fiber can be integrated into fabrics to harvest thermal energy of human body to generate an output voltage of 3.09 mV at a temperature difference of 8 K. This research opens a new avenue for the development of MBPs in power supply.

Study on drainage consolidation characteristics and pore-pressure reversal control of water-rich loess under the combined action of electroosmosis–vacuum

The phenomenon of “pore pressure reversal” occurs in the later stage of electroosmosis–vacuum combined drainage of water-rich loess, which causes the mutual interference of water flow directions in the later stage of the drainage process. Based on the theory of porous media and unsaturated soil mechanics, this study establishes a mathematical model for the coupling of the electric, pore pressure, and displacement fields in the drainage consolidation process of water-rich loess under the combined action of electroosmosis and vacuum. The conservation equations of energy, momentum, and mass are coupled under a solid-liquid-gas three-phase system, considering nonlinear variations of parameters, such as electrical permeability coefficients, electrical conductivity, and hydraulic permeability coefficients. Subsequently, the drainage consolidation process of water-rich loess under different electroosmosis and vacuum combination methods is simulated using finite element software. Moreover, applying vacuum loads in a graded manner and conducting electroosmosis at a later stage of the loading procedure can effectively delay the generation of the “pore pressure reversal” phenomenon and the formation of silt layers.

Achieving High Isotropic Figure of Merit in Cd and in Codoped Polycrystalline SnSe.

Here, we combined Cd and In codoping with a simple hydrothermal synthesis method to prepare SnSe powders composed of nanorod-like flowers. After spark plasma sintering, its internal grains inherited well the morphological features of the precursor, and the multiscale microstructure included nanorod-shaped grains, high-density dislocations, and stacking faults, as well as abundant nanoprecipitates, resulting in an ultralow thermal conductivity of 0.15 W m-1 K-1 for the synthesized material. At the same time, Cd and In synergistically regulated the electrical conductivity and Seebeck coefficient of SnSe, leading to an enhanced power factor. Among them, Sn0.94Cd0.03In0.03Se achieved a peak ZT of 1.50 parallel to the pressing direction, representing an 87.5% improvement compared with pure SnSe. Notably, the material possesses isotropic ZT values parallel and perpendicular to the pressing direction, overcoming the characteristic anisotropy in thermal performance observed in previous polycrystalline SnSe-based materials. Our results provide a new strategy for optimizing the performance of thermoelectric materials through structural engineering.

Kaolin Clay-Based Geopolymer for Ionic Thermoelectric Energy Harvesting.

Geopolymers, a class of sustainable inorganic materials derived from natural and recycled resources, hold promise for various applications, including thermoelectric power generation. This study delves into the thermoelectric properties of Ikere white (IKW)-geopolymer, derived from kaolin clay, by employing rigorous measurements of thermal conductivity, electrical conductivity, and Seebeck coefficient. The investigation elucidates the pivotal role of temperature and ions in shaping the thermoelectric performance of IKW-geopolymer. Electrical conductivity analysis pinpoints ions within the geopolymer's channels as primary contributors. Beyond a critical temperature, the evaporation of bulk water triggers a transition of charge carriers from one- to three-dimensional motion, resulting in reduced conductivity. The Seebeck coefficient exhibits a range from -182 to 42 μV/K, with its time-dependent profile suggesting that ions potentially drive thermoelectricity in cementitious materials. Notably, a unique transition from n-type to p-type behavior was observed in the geopolymer, opening new avenues for ionic thermoelectric capacitors. These insights advance our understanding of thermoelectric behavior in geopolymers and have the potential to propel the development of novel building materials for energy conversion applications.

Dynamics of changes in the temperature coefficient of electrical conductivity of distilled water in conductometric cells during heating and cooling

The problem of taking into account the influence of air on the properties of distilled water is considered, namely the lack of a single generally accepted method for calculating such an influence. The sensitivity of the structure of water to the influence of external factors is described and the possibility of recording and studying such factors by changes in the temperature coefficient of electrical conductivity of water is shown. The dependences of the temperature coefficient of electrical conductivity of distilled water on the rate of change in water temperature, the degree of filling of conductometric cells, as well as on the intensity of the exchange of carbon dioxide between water and air across their interface have been studied. It is noted that these metabolic processes are currently insufficiently studied. A hardware-software measuring complex has been developed and manufactured to study the temperature coefficient of electrical conductivity of water when its temperature changes within the range of 20–55 °C. The temperature coefficient of electrical conductivity of water in sealed conductometric cells was measured at different degrees of filling the cells with distilled water and the rate of heating and cooling of water. The degree of filling of the cells varied within the range of 10–100 %, the rate of change in water temperature varied within the range of 0.04–2.00 °C/min. With a constant heating and cooling time of 15 minutes in all experiments, the change in speed was achieved by changing the temperature of the heating element. The integral temperature coefficient of electrical conductivity is calculated based on the initial and final values of electrical conductivity and water temperature in each measurement cycle. The dependences of the temperature coefficient of electrical conductivity on the rate of change in water temperature at several constant degrees of cell filling were obtained. It has been shown that with a constant ratio of the volumes of water and air in the cell and an increase in the rate of heating of water, the temperature coefficient of electrical conductivity of water decreases by 19–22 %. It has been established that at a constant rate of water heating, with a decrease in the volume of water in the cell, the temperature coefficient of electrical conductivity of water decreases by 40–42 %. The results obtained can be used to quantify the dissociation coefficient of carbonic acid, the mobility of hydrogen ions, as well as the intensity of the gas exchange process under various external influences on water. Refinement of data on the electrical conductive properties of water and processes at the water/air interface is necessary for the development of models of atmospheric phenomena and climate change, as well as for the creation of sensors for weak changes in environmental parameters for the purposes of both environmental monitoring and medical diagnostics.

Insights into phosphorus doping on the structure and electrochemical performance of Li2FeSiO4/C nano-composites

Li2FeSiO4 is one of the most promising cathode materials for lithium ion batteries due to its high theoretical capacity. However, the low electrical conductivity and low lithium-ion diffusion coefficient restrict its practical applications. Hetero-ion doping distinctly affect the crystal and electrochemical properties of Li2FeSiO4 based materials. Herein, phosphorus (P) doped Li2FeSiO4/C nano-composites (Li1.95FeSi0.95P0.05O4/C, abbreviated as LFSPC) and Li2FeSiO4/C nano-composites (LFSC) were synthesized and investigated as cathode material for lithium ion batteries. XRD and XPS analyses indicate that P has been doped in the crystal Li2FeSiO4. SEM results prove that the particle size of LFSPC is smaller than that of LFSC. These features make LFSPC exhibit better electrochemical performance over LFSC. The discharge capacity of LFSPC at 0.1C is as high as 218.1 mAh/g, higher than that of LFSC (144.0 mAh/g). The capacity retention ratio for LFSPC after 200 cycles at 1C is 85 %, higher than that of LFSC (78 %). In addition, LFSPC deliver larger rate performance, lower charge transfer resistance and larger lithium-ion diffusion coefficient.

Enhancing thermoelectric performance of single-walled carbon nanotube films by poly(styrene sulfonate acid) dispersing and sequential base treatment

Despite single-walled carbon nanotubes (SWCNTs) have attracted great interest for thermoelectric (TE) conversion, the strong van der Waals forces between SWCNTs cause them to aggregate into bundles with poor dispersibility, which dramatically deteriorates the charge carrier transport, and thereby induces low electrical conductivity and TE power factor. Herein, we report a facile and efficient approach to enhance TE performance of SWCNTs via the addition of poly(styrene sulfonic acid) (PSSH) and sequential base treatment. PSSH is served as a dispersant and dopant to improve the dispersibility of SWCNTs and facilitate charge carrier conduction, contributing to high electrical conductivity of 3749 ± 122 S cm−1 and power factor of 117.7 ± 3.4 μW m−1 K−2 for 20 wt% PSSH/SWCNT composite film. Further base treatment induces partial removal of insulative PSSH and de-doping effect of SWCNTs, which decreases the barriers between adjacent nanotubes junctions and modulates charge carrier transport to synergistically optimize the electrical conductivity and Seebeck coefficient. With fine-tuning base treatment temperature, the PSSH/SWCNT composite film reaches highest power factor of 160.6 ± 7.9 μW m−1 K−2, higher than pristine SWCNTs of 70.2 ± 4.4 μW m−1 K−2. This work demonstrates the feasibility of this approach to boost the TE properties of SWCNTs, exhibiting potential application for high performance renewable energy harvesting.