Activation Energy For Conduction Research Articles

Physical properties of deep eutectic solvents with efficient nitrogen removal capability

The efficient separation of N-compounds from fuel oil is of great significance for environmental protection and the development of sustainable chemical processes. In this work, eight quaternary acidic deep eutectic solvents (DESs) were prepared for the removal of basic N-compounds (pyridine) from simulated oils. Initially, the density, viscosity, conductivity, surface tension and refractive index values of the DESs were determined at 293.15–333.15 K. Based on these data, physical quantities such as molecular volume, standard entropy, lattice energy, activation energy of viscous flow, activation energy of conductivity, surface entropy, surface energy, speed of sound, molar Gibbs free energy, molar polarizability, molar polarizability, and free molar volume have been calculated. The effects of temperature, alkyl chain length of hydrogen bond acceptors (HBAs)/hydrogen bond donors (HBDs), structure of HBDs, and HBAs anion on the physical properties of DESs were systematically investigated. The internal interaction and property change of DESs are further studied. Finally, pyridine was extracted from the simulated oil using the prepared DESs. DESs consisting of tetrabutylammonium bromide and lactic acid had the highest extraction capacity under the same conditions. The extraction efficiency was found to be strongly correlated with the alkyl chain length and the acidity of the HBDs. This work is expected to provide information on the removal of N-compounds from both theoretical and industrial perspectives.

Development of Mn-Co and Mn-Co-CeO2 Coatings on Crofer 22 APU Steel for Solid Oxide Fuel Cell Interconnects

The present study compared the performance of uncoated, Mn-Co and Mn-Co-CeO2-coated Crofer 22 APU ferritic stainless steel interconnects. The samples were oxidized for 500 h in an electric furnace at 800 °C. The surface morphology and phase structure of the samples before and after oxidation were examined using FESEM microscopy and X-ray diffraction (XRD) analysis, respectively. The electrical conductivity evaluation of the samples was also conducted by measuring the area specific resistance (ASR). The results indicated that the weight gain of the uncoated, Mn-Co and Mn-Co-CeO2-coated samples after 500 h of oxidation was 0.55, 0.58 and 0.27 mg.cm−2, respectively. Additionally, a comparison of the oxidation kinetics of the experimental samples revealed that the oxidation rate constant of the Mn-Co-CeO2-coated steel is 10 and 40 times lower than that of the Mn-Co-coated and uncoated steel, respectively. XRD analysis of the samples after oxidation confirmed the presence of MnCo2O4, Co3O4, and (Mn,Cr,Co)3O4 in the oxidized Mn-Co-coated, MnCo2O4, Co3O4, and CeO2 in the oxidized Mn-Co-CeO2-coated, and the chromium-containing phases (FeCr2O4, MnCr2O4, and Cr2O3) in the oxidized uncoated samples. The presence of phases with high electrical conductivity in the oxidized coated samples reduced their activation energy for conduction compared to the oxidized uncoated sample.

A comparative study on the surface chemistry and electronic transport properties of Bi2Te3 synthesized through hydrothermal and thermolysis routes

Bismuth telluride-Bi2Te3 is the most promising material for harvesting thermal energy near room temperature. There are numerous works on Bi2Te3 reporting significantly different transport properties, with no clear connection to the synthetic routes used and the resultant surface chemistry of the synthesized materials. It is of utmost importance to characterize the constituent particles’ surface and interfaces to get a better understanding of their influence on the transport properties, that will significantly improve the material design starting from the synthesis step. Electrophoretic deposition (EPD) is a promising technique, enabling the formation of thick films using colloidally stabilized suspensions of pre-made nanoparticles, which can enable the study of the effect of surface chemistry, in connection to the synthetic route, on the material’s transport properties. In order to explore the differences in surface chemistry and the resultant transport properties in relation to the synthetic scheme used, here we report on Bi2Te3 synthesised through two wet-chemical routes in water (Hydro-) and oil (Thermo-) as the solvents. XRD analysis showed a high phase purity of the synthesized materials. SEM analysis revealed hexagonal platelet morphology of the synthesized materials, which were then used to fabricate EPD films. Characterization of the EPD films reveal significant differences between the Hydro- and Thermo-Bi2Te3 samples, leading to about 8 times better electrical conductivity values in the Thermo-Bi2Te3. XPS analysis revealed a higher metal oxides content in the Hydro-Bi2Te3 sample, contributing to the formation of a resistive layer, thus lowering the electrical conductivity. Arrhenius plots of electrical conductivity vs inverse temperature was used for the estimation of the activation energy for conduction, revealing a higher activation energy need for the Hydro-Bi2Te3 film, in agreement with the resistive barrier oxide content. Both the samples exhibited negative Seebeck coefficient (S) in the order of 160–170 mV/K. The small difference in S of Hydro- and Themo-Bi2Te3 films was explained by the effective medium theory, revealing that the magnitude of S is linearly correlated with the surface oxide content. Based on the findings, TE materials synthesized through thermolysis route is recommended for further studies using soft treatment/processing of pre-made TE materials. EPD platform presented here is shown to clearly expose the differences in the electronic transport in connection to nanoparticle surface chemistry, proving a promising methodology for the evaluation of morphology, size and surface chemistry dependence of electronic transport for a wide range of materials.

Density functional theory investigation of activation energy for dc conductivity in rare-earth ion-doped Na2ZnP2O7 glasses

Density functional theory investigation of activation energy for dc conductivity in rare-earth ion-doped Na2ZnP2O7 glasses

Lithium disilicate as an alternative silicate battery material. A theoretical study

Advanced atomistic simulations are used to study the ion transport in the Na- and K-doped lithium disilicate Li2Si2O5 which is considered as a potential battery material for solid state alkali batteries. In order to evaluate the ease with which Li2Si2O5 can store Na and K ions, the Na and K incorporation mechanisms into Li2Si2O5 are studied by using lattice statics simulations. Our calculations revealed that the defect formation energies for K and Na doping of Li2Si2O5 amount to 0.49 eV/dopant and 0.96 eV/dopant, respectively. The Li ion diffusion in Li2Si2O5 is significantly enhanced upon Na and K doping. The activation energies of Li ion diffusion in all samples are in the range of 0.5–0.6 eV, while for conduction 0.4–0.5 eV. At higher dopant concentrations, K doping increases the Li ion diffusion/conduction, reaching their improved transport properties at x = 0.14 with low activation energy for diffusion and conduction. At a low dopant concentration of x = 0.02, Na doping also improves the Li ion diffusion/conduction. Our results demonstrate the potential of the doped lithoum disilicate Li2Si2O5 as an effective material for alkali ion batteries and strongly suggest experimental verification.

Y and La Doping in CaMnO3 Compounds: Effects of Dopant Identity and Amount on Charge Transport Kinetics

Enhancing electronic transport properties of thermoelectric oxides is of great technological importance. Oxides are promising candidates for waste heat harvesting at elevated temperatures as well as for electricity generation in low‐power applications. To this purpose, fundamental understanding of their electrical and thermal conduction mechanisms is essential. Herein, the conduction mechanism of CaMnO3 materials is focused on and how dopant identity and amount alter the kinetic properties of charge transport is investigated. Ca1−xRxMnO3 compounds with R = Y and La are synthesized, where 0 ≤ x ≤ 0.13, and the electrical conductivity and Seebeck coefficient for temperatures ranging from 300 to 1050 K, indicating that Y‐doped compounds are usually more conductive than their La‐doped counterparts, are measured. Analysis of both in terms of the small polaron hopping model reveals that Y doping reduces conduction activation energies, resulting in higher electrical conductivity and charge carrier mobility. Remarkably high values of thermoelectric power factor for the Ca0.97La0.03MnO3 compound, for example, 300 μWm−1 K−2 at 1050 K are observed; furthermore, these values are preserved for a wide temperature range, rendering this compound a good candidate for heat‐to‐electrical power generation at elevated temperatures.

A Phosphine‐Amine‐Linked Covalent Organic Framework with Staggered Stacking Structure for Lithium‐Ion Conduction

AbstractIn‐plane ionic conduction over two‐dimensional (2D) materials is desirable for flexible electronics. Exfoliating 2D covalent organic frameworks (COFs) towards a few layers is highly anticipated, whereas most examples remain robust via π‐stacking against the interlayered dislocation. Herein, we synthesize a phosphine‐amine‐linked 2D COF by a nucleophilic substitution reaction of phosphazene with amines. The synthesized COF is crystalline, and stacks in an AB‐staggered fashion, wherein the AB dual layers are interlocked by embedding P−Cl bonds from one to another layer, and the non‐interlocked layers are readily delaminated. Therefore, in situ post‐quaternization over phosphazene can improve the ionization of backbones, accompanied by layered exfoliation. The ultrathin nanosheets can decouple lithium salts for fast solid‐state ion transport, achieving a high conductivity and low activation energy. Our findings explore the P−N substitution reaction for COF crystallization and demonstrate that the staggered stacking 2D COFs are readily exfoliated for designing solid electrolytes.

A Phosphine-Amine-Linked Covalent Organic Framework with Staggered Stacking Structure for Lithium-Ion Conduction.

In-plane ionic conduction over two-dimensional (2D) materials is desirable for flexible electronics. Exfoliating 2D covalent organic frameworks (COFs) towards a few layers is highly anticipated, whereas most examples remain robust via π-stacking against the interlayered dislocation. Herein, we synthesize a phosphine-amine-linked 2D COF by a nucleophilic substitution reaction of phosphazene with amines. The synthesized COF is crystalline, and stacks in an AB-staggered fashion, wherein the AB dual layers are interlocked by embedding P-Cl bonds from one to another layer, and the non-interlocked layers are readily delaminated. Therefore, in situ post-quaternization over phosphazene can improve the ionization of backbones, accompanied by layered exfoliation. The ultrathin nanosheets can decouple lithium salts for fast solid-state ion transport, achieving a high conductivity and low activation energy. Our findings explore the P-N substitution reaction for COF crystallization and demonstrate that the staggered stacking 2D COFs are readily exfoliated for designing solid electrolytes.

Structural, micro-structural, morphological, electrical spectroscopy and optical analysis of lithium-titanium oxide electronic material

In this paper, we perform a thorough analysis into the electrical properties of high-purity, thick Li2TiO3 discs generated by the mixed oxide process, covering a wide range of frequencies and temperatures. Li2TiO3 samples are calcined and sintered at 920 °C and 940 °C. X-ray diffraction shows a monoclinic crystal structure with a space group of C2/c(15), matching JCPDS card (00-033-0831). The Scherrer and W-H plot methods provide consistent crystallite sizes of 51.23 and 49.34 nm. SEM and EDAX at room temperature reveal the material's structure and chemistry. The microstructure has well-defined porosity and homogeneous grain dispersion, with an average grain size of 2.82 µm. We studied frequencies from 1 kHz to 1 MHz and temperatures from 30 °C to 450 °C. Measure dielectric constant, tangent loss, and electrical conductivity. Above 350 °C, the dielectric constant increases significantly. Between 400 °C and 450 °C, electrical conductivity activation energy ranges from 0.431 to 0.624 eV. UV–Visible spectroscopy shows maximal absorption at 201 nm, indicating a band gap value of 3.78 eV. Its residual, saturation, and coercivity values were 0.00286 µc/cm2, 0.0267 µc/cm2, and 0.974 kV/cm, respectively, from the hysteresis loop. The UV spectrum shows Li2TiO3 absorbs most light at 201 nm and has a 3.82 eV band gap. Its composition and chemical processes are confirmed by FTIR peaks at various wavenumbers. Based on these results Li2TiO3 might have the potential applications in electronic devices such as capacitors, insulators, and electrochemical sensors as well as humidity and gas monitoring devices.

Synthesis, dielectric and impedance spectroscopy study of temperature stable Ta2O5 modified 0.85BaTiO3-0.15Bi(Mg0.5Ti0.5)O3 ceramics

In the present study, 0.85BaTiO3–0.15Bi(Mg0.5Ti0.5)O3-xTa2O5 (x = 0, 0.01, 0.015, 0.02, 0.025) processed via the conventional mix oxide route. The phase, microstructure, and dielectric properties were studied. Single perovskite phase developed and studied via XRD. A Dense microstructure for each composition was developed with the pseudo-crystal structure. Low grain size <3 μm is achieved for each composition. A high dielectric constant (εr) > 1000 and low dielectric loss (tanδ <2.5 %) is obtained for x ≤ 0.020, with high stability over a broad range of temperatures (<0 °C to 180 °C). These compositions are considered to be suitable for designing X9R capacitors. In complex impedance analysis, the decreasing value of the bulk impedance upon increasing the temperature revealed the negative temperature coefficient of resistance (NTCR) behavior. The small conductivity and high activation energy value for x = 0.01 demonstrate the temperature stability of this ceramic.

ELECTROCONDUCTIVITY OF MOLTEN FLiNaK AND FLiNaK–CeF&lt;sub&gt;3&lt;/sub&gt;

The eutectic mixture LiF–NaF–KF (FLiNaK) is promising as a carrier salt for molten-salt reactors. Cerium fluoride CeF3 can be considered as a simulant of plutonium fluoride PuF3. In this work, the temperature dependence of the electrical conductivity of the molten ternary eutectic LiF–KF–NaF containing from 0 to 25 mol % cerium fluoride in the temperature range 480–777°C. FliNaK–CeF3 mixtures containing up to 25 mol. % of cerium fluoride were prepared directly in the experimental cell, dropping the required amount of CeF3 into the melt and keeping mixtures of a given composition for 12 h at temperatures exceeding the liquidus temperatures of the studied compositions. The electrolyte resistance was determined from impedance hodographs, which were taken using the Z-1500J impedance meter. A two-electrode cell with Pt electrodes was used. Analysis of the experimental values of the electrical conductivity of double and triple fluoride melts KF–LiF available in the literature; KF–NaF; LiF–NaF–KF shows that our data on the electrical conductivity of the LiF–NaF–KF (FLiNaK) eutectic mixture are consistent with the general trend in electrical conductivity with increasing KF concentration in the melt. A significant decrease in the specific electrical conductivity of the molten system and a slight increase in the activation energy of electrical conductivity with an increase in the concentration of cerium fluoride are shown. The temperature dependences of the electrical conductivity of the molten system were approximated by second-order polynomials. The formation of the \({\text{CeF}}_{6}^{{3 - }}\) complex ion in the melt was confirmed by spectral studies. The Raman spectra of molten FLiNaK and FliNaK–CeF3 mixtures containing 8 and 15 mol. % of cerium fluoride were recorded. With an increase in the concentration of CeF3 in the melt, the amount of \({\text{CeF}}_{6}^{{3 - }}\) complex ions increases, which leads to an increase in the intensity of the observed vibrational bands.

Crystal structure, chemical bonding and infrared reflectivity of microwave dielectric SrIn2O4 ceramics

In this work, the orthorhombic structured SrIn2O4 ceramics with a space group Pnam were synthesized by a solid-state reaction method. A high relative density (96.5%) coupled with excellent microwave dielectric properties (εr ~ 12.3, Q × f = 96,900 GHz, τf ~ -61.6 ppm/°C) were obtained as sintered 1300 °C for 4 h. The bond valence analysis demonstrates that the large sized cation Sr2+ exhibits a compressed state, while the In3+ exhibits a weaken rattling effect. The P-V-L chemical bond theory analysis indicates that the In-O bonds play a key role in affecting the dielectric loss. The thermally conductivity activation energy Edc (0.94 eV) of SrIn2O4 was obtained by the dielectric spectroscopy, indicating that the Edc was contributed to the double ionized oxygen vacancies. Furthermore, the intrinsic dielectric properties (εr ~ 11.2, Q × f = 148,900 GHz) of SrIn2O4 were obtained by infrared reflectivity spectroscopy.

The structure and electrical properties of novel BaSn0.15Ce0.35Hf0.25Y0.1Yb0.1Ho0.05O3-δ high-entropy proton-conducting electrolyte

In this article, the structure and electrical properties of BaSn0.15Ce0.35Hf0.25Y0.1Yb0.1Ho0.05O3-δ (referred as BSCHYYbHo in forthcoming discuss) high-entropy ceramic have been investigated. The BCHYYb (short for BaCe0.5Hf0.3Y0.1Yb0.1O3-δ) and BSCHYYbHo pellets were synthesized successfully by the solid-state reaction method. The XRD detection results indicate that there is no secondary phase appeared in BSCHYYbHo and the lattice constant decrease compared to BCHYYb. The surface SEM and EDS images illustrates that BSCHYYbHo is denser than BCHYYb and the elements distribution is more uniform. The DFT calculation proves that BSCHYYbHo has a tend to maintain single phase structure. The electrical properties of BSCHYYbHo is obtained by the DRT analysis and equivalent circuit method based on defect equilibria model. The total conductivity of BSCHYYbHo is about 2.02 × 10-4 ∼1.01 × 10-2 S·cm-1 and standard molar hydration enthalpy of BSCHYYbHo is recorded as − 81.8 kJ/mol. Further, the proton, oxygen vacancies and electron holes conductivity activation energies in BSCHYYbHo is estimated to be 0.45 eV, 1.41 eV and 1.60 eV, respectively. Compared to BCHYYb, BSCHYYbHo electrolyte has higher proton concentration and proton transference number. Overall, BSCHYYbHo ceramic with dense structure and high proton transference number is a potential material for application.

The role of thermal vibrations in transformation of structure transition for sodium nitrate in a restricted geometry

The temperature evolution of the crystal structure and dielectric response of a nanocomposite based on porous glasses with an average pore diameter of 7 nm and embedded sodium nitrate in the temperature range of 300–600 K have been studied on heating. The temperature dependences of the amplitudes of thermal vibrations of ions in sodium nitrate nanoparticles are obtained, and the activation energies of sodium hopping conductivity in these nanocomposite materials are determined. The results obtained allow us to state that it is the sharp increase in thermal vibrations that leads to the appearance of the previously observed crossover in the temperature dependence of the order parameter of the structural transition in sodium nitrate nanoparticles at T* ∼455 K and to a decrease in the activation energy of sodium ions hopping conductivity on heating above T*.

INVESTIGATION OF THE SPECIFIC ELECTRICAL CONDUCTIVITY OF RHENIUM-CONTAINING SOLUTIONS OF AMMONIUM CARBONATE AND CALCULATION OF ITS ACTIVATION ENERGY

The specific electrical conductivity dependence of aqueous solutions of ammonium carbonate and solutions of the ammonium carbonate—ammonium perrenate system on the reagents content in the range of their concentration of 0.1—1.8 mol/l for (NH4)2CO3, 0.01—0.1 mol/l for NH4ReO4 and solution temperatures in the range of 20-50 °C were investigated by the conductometric method. A linear increase in electrical conductivity with an increase in the temperature of electrolytes and a nonlinear increase with an increase in the concentration of reagents was revealed. The temperature coefficients values of electrical conductivity and the activation energy values of electrical conductivity in the studied range of concentrations and temperatures are calculated. A decrease in the activation energy of electrical conductivity with an increase in the temperature of the solution was noted. The calculated value of the activation energy of electrical conductivity indicates the diffusive nature of charge transfer.

Phase regulation enabling dense polymer-based composite electrolytes for solid-state lithium metal batteries

Solid polymer electrolytes with large-scale processability and interfacial compatibility are promising candidates for solid-state lithium metal batteries. Among various systems, poly(vinylidene fluoride)-based polymer electrolytes with residual solvent are appealing for room-temperature battery operations. However, their porous structure and limited ionic conductivity hinder practical application. Herein, we propose a phase regulation strategy to disrupt the symmetry of poly(vinylidene fluoride) chains and obtain the dense composite electrolyte through the incorporation of MoSe2 sheets. The electrolyte with high dielectric constant can optimize the solvation structures to achieve high ionic conductivity and low activation energy. The in-situ reactions between MoSe2 and Li metal generate Li2Se fast conductor in solid electrolyte interphase, which improves the Coulombic efficiency and interfacial kinetics. The solid-state Li||Li cells achieve robust cycling at 1 mA cm−2, and the Li||LiNi0.8Co0.1Mn0.1O2 full cells show practical performance at high rate (3C), high loading (2.6 mAh cm−2) and in pouch cell.

Native defects association enabled room-temperature p-type conductivity in β-Ga2O3

The room temperature hole conductivity of the ultra-wide bandgap semiconductor β-Ga2O3 is a pre-requisite for developing the next-generation electronic and optoelectronic devices based on this oxide. In this work, high-quality p-type β-Ga2O3 thin films grown on r-plane sapphire substrate by metalorganic chemical vapor deposition (MOCVD) exhibit ρ = 5 × 104 Ω·cm resistivity at room temperature. A low activation energy of conductivity as Ea2 = 170 ± 2 meV was determined, associated to the VO++−VGa−native acceptor defect complex. Further, taking advantage of cation (Zn) doping, the conductivity of Ga2O3:Zn film was remarkably increased by three orders of magnitude, showing a long-time stable room-temperature hole conductivity with the conductivity activation energy of around 86 meV. VO++−ZnGa− defect complex has been proposed as a corresponding shallow acceptor.

The effect of Nb2O5, CaO/SiO2, and TiO2 on the electrical conductivity of CaO-SiO2-Nb2O5-TiO2-CeO2-CaF2 melt

Electrical conductivity is a very important physical parameter in the process of electrolytic extraction of niobium from molten niobium-enriched slag or preparation of ferroniobium alloy by reduction melting separation in electric arc furnace. The effects of Nb2O5, CaO/SiO2 ratio and TiO2 on the electrical conductivity of CaO-SiO2-Nb2O5-TiO2-CeO2-CaF2 melt were studied by AC four-electrode method. The melt structure was studied by XPS to reveal the change rules of melt conductivity. The results show that the addition of Nb2O5 or increasing the CaO/SiO2 ratio in the melt can depolymerize the melt network structure and effectively improve the melt conductivity, and the activation energy of the conductivity is negatively correlated with the Nb2O5 content and the CaO/SiO2 ratio. With the increase of TiO2 content in the melt, the melt network structure polymerizes, the melt conductivity decreases, and the activation energy of conductivity also showed a decreasing trend.

Electrical performance and conductive mechanism of xLaCoO3-(1-x)Ba0.98Ca0.02Ti0.96Sn0.04O3 ceramics with NTC effect via chemical modification

xLaCoO3-(1-x)Ba0.98Ca0.02Ti0.96Sn0.04O3 (xLCO-(1-x)BCTS) ceramics were manufactured using a solid-phase reaction method. All samples exhibited single cubic perovskite structures and a typical negative temperature coefficient (NTC) effect. The grain sizes increased with increasing LCO doping content. For all samples, the resistivities (ρ25), activation energies for electrical conduction (Ea), thermal constants (B25/75), and activation energies of the relaxation process (Erelax) were in the ranges of 5.93 × 104-9.36 × 108 Ω•cm, 0.3700–0.2951 eV, 3177–3988 K, and 0.3539–0.2890 eV, respectively. Such a combination of ρ and B renders these materials to be potential candidates for NTC thermistors. According to the XPS spectra and due to the difference in ion radius among Co3+, Co4+, Ti3+, and Ti4+, Co3+-O-Co2+ and Ti3+-O-Ti4+ bonds were formed, and the electrons in the continuous bonds generated jumping conduction. The fitted results of the equivalent circuit showed that Rg and Rgb decreased with increasing LCO content, which is consistent with the DC resistivity at 25 °C. The results of the analysis indicate that the conductive mechanism of xLCO-(1-x)BCTS ceramics was electron hopping conduction.

The conduction mechanism and dielectric behavior of cadmium bismuth silicate glasses

By using the traditional melt-quench method, cadmium bismuth silicate glasses with composition; 20CdO·(80-x)Bi2O3·xSiO2 (10≤x≤50 mol%) were fabricated. Impedance spectroscopy was used to examine the conduction and relaxation mechanisms in prepared glasses over the range of frequency 10Hz–7MHz and temperature 473–703 K. Values of dc conductivity (σdc), the activation energy for dc conduction (Edc), frequency exponent parameter (s), and relaxation energy (Eτ) were extracted from the experimental impedance data. The conductivity spectra follow Jonscher’s power law and the obtained conductivity values were found to be compositional dependent ascribed to the existence of mixed former effect in understudy glasses. The frequency exponent parameter increases with frequency and approaches unity at higher frequencies. For each glass composition, almost equal values of Eτ and Edc show that the charge carriers have to cross a similar energy barrier in relaxation and conduction processes. The exact overlaying of normalized electrical modulus plots as a single master curve signifies temperature-independent dynamical processes at various frequencies.