Impurity Resistivity Research Articles

The resistivity of rare earth impurities diluted in Lanthanum, Part I

We study the temperature-independent resistivity of rare-earth magnetic impurities (Gd, Tb, Dy) and the non-magnetic impurity (Lu) diluted in double hexagonal close-packed (dhcp) lanthanum. We model the system as a two-band system, where s-electrons perform conduction while d-electrons entirely screen the charge differences induced by impurities. Using the T-matrix formalism derived from the Dyson equation, we obtain an expression for resistivity. Since electronic properties are highly sensitive to band structure, we examine two types: a simplified “parabolic” band structure and a more realistic one obtained through first-principles calculations using VASP. Our results indicate that the exchange parameters, represented as cross products, significantly influence the magnitude of the spin resistivity term. Furthermore, we find that the role of band structure in resonant scattering and the formation of virtual bound states depends on the specific band structure employed. Additionally, our study addresses the effects of translational symmetry breaking and the excess charge introduced by rare-earth impurities on resistivity.

Advancements in Solid Oxide Fuel Cell Technology: Bridging Performance Gaps for Enhanced Environmental Sustainability

In light of the anticipated 50% increase in global energy demand by 2050, the demand for innovative, environmentally conscious, efficient, and dependable energy technologies is paramount. Solid oxide fuel cells (SOFCs) offer a promising solution for sustainable energy production. This comprehensive review provides a detailed analysis of SOFCs, covering their fundamentals, materials, performance, and diverse applications, while also addressing technological challenges and future prospects. The review emphasizes the key advantages of SOFCs, including their high efficiency of up to 60% and minimal environmental impact. It explores the significance of impurity resistance and durability in materials and manufacturing processes for SOFC components. Comparative evaluations demonstrate the superior energy efficiency and ecological effects of SOFCs compared to other fuel cell technologies. SOFCs’ versatility and potential are showcased through their applications in transportation, power generation and storage, portable devices, and residential usage. However, challenges such as cost, longevity, reliability, and integration with other energy systems are identified, emphasizing the need for supportive policies and regulations.

Lipid analyses of oil-bearing biomass using a thermally induced derivatization method

This study assessed the efficacy of a commercial fatty acid (FA) methylation kit for analyzing insect/microalgal biomass lipids by comparing it to a thermally induced derivatization method, which is known for its high conversion yield and impurity resistance and serves as a benchmark for evaluating kit performance, as a comparative standard. In insect lipid analysis, kit-based derivatization demonstrated a lower yield of FA methyl esters (FAMEs) than that of the thermally induced method, which is attributable to inherent technical limitations (vulnerability to impurities). This yield discrepancy was further highlighted in microalgal lipid analyses. The efficiency of FA derivatization using the kit-based method was contingent on the lipid structure, as evidenced by the diminished conversion yields for wax esters in Euglena gracilis. Furthermore, for Chlamydomonas reinhardtii, the lower FAME yield observed with kit-based derivatization suggested potential inadequacies in lipid extraction, particularly in the presence of rigid cellular structures such as cell walls. This reduced interaction between lipids and methanol could lead to diminished FAME conversion yields. These findings highlight the notable influence of the biomass type and lipid structure on the efficiency of kit-based derivatization, potentially yielding suboptimal results in lipid analysis.

Nickel-embedded zeolite subcrystal catalyst: rapid enhancement of activity and metal impurity resistance in the hydrodesulfurization of 4,6-dimethyldibenzothiophene

Ni nanoparticles embedded in an Al-containing MFI zeolite subcrystal (<7 nm) lead to superior hydrodesulfurization activity and exceptional resistance to Ni/V metal impurities.

Impurity Resistivity of the Earth's Inner Core

AbstractSeismic observations suggest that the Earth's inner core has a complex structure (e.g., the isotropic layer at the top, innermost inner core, and hemispherical dichotomy). These characteristics are believed to reflect the history of dynamics and temperature profile of the inner core. One critical physical property is the inner core's thermal conductivity. The thermal conductivity of metals can be estimated from their electrical resistivity using the Wiedemann‐Franz law. Recent high‐pressure and temperature experiments revealed that the temperature dependence of electrical resistivity is small for Fe‐Si alloys. The small temperature coefficient means that it is essential to determine the impurity resistivity of Fe alloys to constrain the inner core's thermal conductivity. Therefore, this study systematically calculated the impurity resistivities of 4‐ and 6‐component alloys at inner core pressure by combining the Korringa‐Kohn‐Rostoker method with the coherent potential approximation. As a result, we obtained the thermal conductivity of the inner core to be 150–263 W/m/K. The inner core cannot maintain thermal convection with such a high thermal conductivity, resulting in a flat temperature profile. In materials science, it is widely known that polycrystals soften suddenly at high temperatures a few percent below their melting temperature. If such a pre‐melting occurs in the inner core, the flat temperature profile due to high thermal conductivity causes variations in the attenuation within the inner core. This may explain the observation that the upper inner core is more strongly attenuated than the innermost inner core.

SIMULATION OF ELECTRO-THERMAL CONDITION IN A FAULTY LOW-CURRENT CONTACT

It has been suggested in earlier literature that the accuracy of the thermal simulation of electrical connectors is closely related to contact resistance. Contact resistance in electrical connectors occurs due to both constriction resistance (caused by narrow paths in which the current flows through the electrical connector) and film resistance (oxidized metals caused by the high resistivity of materials and impurities from the atmosphere etc.). This paper reviews the oxidation and wear affecting electrical connectors by proposing a thermal-electrical coupled finite element simulation (FEM) of the contact temperature rise of a simple contact model in COMSOL Multiphysics.

Kondo effect in a spin-3/2 Fermi gas

We investigate the Kondo effect of a spin-3/2 Fermi gas and give a detailed calculation of the impurity resistance and ground state energy based on the s-d exchange model. It is found that the impurity resistance increases logarithmically with the decrease of temperature in the case of antiferromagnetic coupling similar to the spin-1/2 system but has a larger resistance minimum value due to the increase of spin scattering channels. In the case of antiferromagnetic interaction, the ground state is still the Kondo singlet state while the septuplet state has the lowest energy for ferromagnetic coupling. And with the same antiferromagnetic s-d coupling parameter, the energy of the Kondo singlet state is lower than spin-1/2, which indicates that the larger spin, the easier it is to enter the Kondo-screened phase. This provides some theoretical support for the realization of the Kondo effect with ultra-cold atoms.

Fabrication and performance of atmospheric plasma sprayed solid oxide fuel cells with liquid antimony anodes

A solid oxide fuel cell (SOFC) with a liquid antimony anode (LAA) is a potential energy conversion technology for the use of impurity-containing fuels. Atmospheric plasma spraying (APS) technology has become a promising LAA-SOFC preparation method because of its economy and convenience. In this paper, button SOFCs with different cathode materials and ratios of pore former were prepared by the APS method and were operated at 750 °C. The effect of the cathode structure on the electrochemical performance of the LAA-SOFCs was analyzed, and an optimized spraying method for LAA-SOFCs was developed. A tubular LAA-SOFC was prepared using the APS method based on the optimized spraying method, and a peak power of 2.5 W was reached. The tubular cell was also measured at a constant current of 2 A for 20 h and was fed with a sulfur-containing fuel to demonstrate its impurity resistance and electrode stability.

Morphological and Permeability Fraction of Mixed Matrix Polysulfone Membrane on Batik Palembang Wastewater Treatment

High performance polysulfone (PSf) membrane has been prepared for treating of batik palembang wastewater. Many investigations attempted the use of polysulfone (PSf) membranes to filtrate dilute contaminant in textile wastewater. The matrix membrane is a mixture of PSf which is produced by adding inorganic materials to obtain a polymer that functions to manufacture the membrane by increasing hydrophilicity and impurity resistance. MMM were fabricated from a dope solution containing PSf/LiCl/DMF at different additives composition. Antifouling properties of membranes could be enhance with 0.0 - 10 wt.% LiCl that has been added into dope solution. Pure water permeation flux analysis (PWP), AFM and FESEM. From the results of research on FESEM, the PSf / LiCL membrane showed a fairly symmetrical cross-sectional structure containing two layers. The layers of the tiny finger-like structure on the edge of the perforated fibers and the holes like the larger fingers are mixed with the macrovoid layer in the middle section. PWP flux is not proportional to mean rough outer surface but higher water permeation. Therefore, PSf/LiCl exhibited a better performance that resulted a much lower fouling tendency than the naked membrane in batik Palembang wastewater treatment.

High-performance multi-layer composite membrane with enhanced interlayer compatibility and surface crosslinking for CO2 separation

Preparation of CO2 separation membrane with high gas permeance and CO2 selectivity is always desirable. In this work, inspired by pesticides and cosmetics, through the use of a variety of additives, good compatibility between the water-based coating solution of low concentration and the hydrophobic surface of the intermediate layer (or gutter layer) had been achieved. A membrane with high gas permeance and moderate CO2 selectivity was prepared preliminarily, and the synergistic mechanism among various additives was clarified. Then, through simple cross-linking modification of the membrane surface, a multi-layer composite membrane for CO2 separation was prepared with CO2 selectivity being improved greatly. The degree of cross-linking on the membrane surface and the thickness of the cross-linked layer was studied by XPS etching analysis. Separation performance for CO2/N2, CO2/CH4, and CO2/H2 mixture had been tested, and the prepared multi-layer composite membrane exhibited excellent CO2 separation performance. Moreover, the simulated flue gas test showed that the prepared membrane was of good long-term stability and impurity resistance.

Electrical and thermal transport properties of Fe–Ni based ternary alloys in the earth's inner core: An ab initio study

Besides iron, the Earth's core also contains 5–10% of nickel and several light elements such as H, C, N, O, Si and S. Fe-Ni alloys have been considered as the host material with 10% Ni. The impurity atoms which are comprised of the light elements have been incorporated at different concentrations in the host alloy, giving rise to ternary alloys. All these systems have been subjected to compression at pressures similar to that in the inner core of the Earth. The atomic concentration of the impurities has been varied from 2.5% to 50%. The formation enthalpies suggest that these ternary alloys are energetically favorable. The impurity resistivity is calculated using the Kubo-Greenwood formula. At approximately ~30% of atomic concentration of impurities, the electrical resistivities start to saturate. For lesser percentage of hydrogen, the impurity resistivity is in the same range as that of the rest. But once the concentration of hydrogen increases, the impurity resistivity becomes very high. Generally, the resistivities are seen to plummet with increasing pressure. Using the Wiedemann-Franz law, the thermal conductivities were also determined from the calculated electrical resistivities for both varying concentration and pressure. On compression, the thermal conductivities increased by approximately 5% in the inner core pressure range.

Low-temperature anomalous spin correlations and Kondo effect in ferromagnetic SrRuO3/LaNiO3/La0.7Sr0.3MnO3 trilayers

A systematic comparative study of the electronic transport and ferromagnetic resonance of ultrathin trilayers (TLs) of ${\mathrm{SrRuO}}_{3}/{\mathrm{LaNiO}}_{3}/{\mathrm{La}}_{0.7}{\mathrm{Sr}}_{0.3}{\mathrm{MnO}}_{3}$ on (001)- and (111)-oriented ${\mathrm{SrTiO}}_{3}$ (STO) substrates has been reported. An unusual upturn in resistivity $\ensuremath{\rho}(T$) at low temperature (so called Kondo-like behavior) accompanied by the negative magnetoresistance has been observed. For temperatures larger than the Kondo temperature $({T}_{\text{K}})$, $\ensuremath{\rho}(T$) is in good agreement with the Hamann's impurity resistivity model $\ensuremath{\rho}(Tg{T}_{\text{K}})\ensuremath{\propto}{(ln(T/{T}_{\text{K}}))}^{\ensuremath{-}2}$ for spin $S=1/2$ and 3/2 for the TLs on (001)-STO and (111)-STO, respectively. At the temperatures $T\ensuremath{\gg}{T}_{\text{K}}$, electron-electron $[\ensuremath{\rho}(T)\ensuremath{\propto}{T}^{2}]$ contribution dominates over those appearing due to the electron-phonon interaction $[\ensuremath{\rho}(T)\ensuremath{\propto}{T}^{5}]$ and 2-Magnon scattering. Using the ferromagnetic resonance near the Curie temperature of ${\mathrm{La}}_{0.7}{\mathrm{Sr}}_{0.3}{\mathrm{MnO}}_{3}$, we evaluated the contribution of surface anisotropies $({K}_{\text{s}})$ as well as in-plane volume anisotropies $({K}_{\ensuremath{\nu}})$ : ${K}_{\text{s}}\ensuremath{\sim}\ensuremath{-}9.57\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}$ ($\ensuremath{-}6.68\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}$) ${\mathrm{J}/\mathrm{m}}^{2}$ and ${K}_{\ensuremath{\nu}}\ensuremath{\sim}4.04\ifmmode\times\else\texttimes\fi{}{10}^{5}\phantom{\rule{0.16em}{0ex}}(3.31\ifmmode\times\else\texttimes\fi{}{10}^{5}$) ${\mathrm{J}/\mathrm{m}}^{3}$ for the TLs on (001)-STO (TLs on (111)-STO). In addition, the Gilbert damping constant is determined which varies between 0.32 (0.23) and 0.16 (0.19) having spin mixing conductance, ${\mathrm{g}}^{\ensuremath{\uparrow}\ensuremath{\downarrow}}=\phantom{\rule{4pt}{0ex}}5.2\ifmmode\times\else\texttimes\fi{}{10}^{19}$ ($13.38\ifmmode\times\else\texttimes\fi{}{10}^{19}$) ${\mathrm{m}}^{\ensuremath{-}2}$ for TLs on (001)-STO ((111)-STO).

Impurity Resistivity of fcc and hcp Fe-Based Alloys: Thermal Stratification at the Top of the Core of Super-Earths

It is widely known that the Earth's Fe dominant core contains a certain amount of light elements such as H, C, N, O, Si, and S. We report the results of first-principles calculations on the band structure and the impurity resistivity of substitutionally disordered hcp and fcc Fe based alloys. The calculation was conducted by using the AkaiKKR (machikaneyama) package, which employed the Korringa-Kohn-Rostoker (KKR) method with the atomic sphere approximation (ASA). The local density approximation (LDA) was adopted for the exchange-correlation potential. The coherent potential approximation (CPA) was used to treat substitutional disorder effect. The impurity resistivity is calculated from the Kubo-Greenwood formula with the vertex correction. In dilute alloys with 1 at. % impurity concentration, calculated impurity resistivities of C, N, O, S are comparable to that of Si. On the other hand, in concentrated alloys up to 30 at. %, Si impurity resistivity is the highest followed by C impurity resistivity. Ni impurity resistivity is the smallest. N, O, and S impurity resistivities lie between Si and Ni. Impurity resistivities of hcp-based alloys show systematically higher values than fcc alloys. We also calculated the electronic specific heat from the density of states (DOS). For pure Fe, the results show the deviation from the Sommerfeld value at high temperature, which is consistent with previous calculation. However, the degree of deviation becomes smaller with increasing impurity concentration. The violation of the Sommerfeld expansion is one of the possible sources of the violation of the Wiedemann-Franz law, but the present results could not resolve the inconsistency between recent electrical resistivity and thermal conductivity measurements. Based on the present thermal conductivity model, we calculated the conductive heat flux at the top of terrestrial cores, which is comparable to the heat flux across the thermal boundary layer at the bottom of the mantle. This indicates that the thermal stratification may develop at the top of the liquid core of super-Earths, and hence, chemical buoyancies associated with the inner core growth and/or precipitations are required to generate the global magnetic field through the geodynamo.

Electrical resistivity of fcc phase iron hydrides at high pressures and temperatures

We measured the electrical resistivity of face-centered-cubic (fcc) structured iron hydrides at high pressures up to 65GPa and high temperatures in a laser-heated diamond anvil cell. The results indicate that the resistivity of stoichiometric fcc FeHx (x ∼ 1.0) is smaller than that of fcc Fe at the same pressure and temperature conditions. The same behavior was also observed in fcc FeNiHx (x ∼ 1.0). On the other hand, hydrogen-poor fcc FeHx (x<0.77) showed a resistivity comparable to that of the fcc phase of pure iron. Therefore, we conclude that the stoichiometric fcc Fe (–Ni) hydride is more conductive than Fe (–Ni) with the same crystal symmetry, and the impurity resistivity of hydrogen in Fe is vanishingly small. Even if hydrogen is the major light element in the Earth's core, it would have little influence on the electrical and thermal conductivity of Fe–Ni alloys, and hence the thermal evolution of the core.

Saturation and pressure effects on the resistivity of titanium and two Ti-Al alloys

The electrical resistivities of α phase titanium and two Ti-Al alloys have been measured as functions of temperature, T, between 4 and 700 K and, in the range 175–700 K, as a function of pressure up to 1.2 GPa. All materials showed resistivity saturation effects at the highest temperatures. A “parallel resistivity” saturation model could be fitted to all data with excellent results if Mott-Fermi smearing, expected for a transition metal, was included by adding a term in T3 to the phonon-induced resistivity. However, in the standard saturation model the fitted resistivity parameters were not always realistic. A modified saturation model which partially retained Matthiessen's rule could be fitted equally well and gave numerically acceptable results for both residual, electron-phonon and saturation resistivities. This new model also fitted the T dependence of the pressure coefficients with a single set of coefficients, each valid for all three materials. Although simple free-electron and Debye models could apparently explain the observed pressure dependence of the impurity and electron-phonon resistivities, a model taking band structure changes with pressure into account showed that the electron-phonon interaction factor of titanium is practically independent of pressure while the plasma frequency has a strong pressure dependence. This model gave reasonable numerical results for the pressure dependence of both the residual, electron-phonon and saturation resistivities and also agreed with experimental data for the superconducting critical temperature Tc under pressure for α titanium.

Electrical Resistivity of Fe‐C Alloy at High Pressure: Effects of Carbon as a Light Element on the Thermal Conductivity of the Earth's Core

AbstractWe measured the electrical resistivity of iron, Fe99C1, Fe3C, and Fe7C3 up to ~80 GPa using the van der Pauw method in a diamond anvil cell. The electrical resistivity of disordered Fe99C1 at high pressure shows a strong impurity resistivity of carbon. The ferromagnetic‐paramagnetic transition in Fe3C and Fe7C3 is associated with the flattening of the resistivity pressure gradient at ~6 GPa. Fe7C3 exhibits the highest electrical resistivity among all iron‐light element alloys, and Fe3C and Fe7C3 disobey the Matthiessen's rule by showing a lower electrical resistivity than a disordered iron‐carbon alloy because of chemical ordering. A comparison of the impurity resistivity between silicon, sulfur, nickel, and carbon shows that carbon has an exceedingly stronger alloying effect than other elements. If the chemical ordering observed in Fe‐Si system is held true for the Fe‐C system, the chemical ordering in Fe7C3 possibly increases the thermal conductivity of the inner core and enlarges the thermal and electrical conductivity gap at the inner‐core boundary. Models of the thermal conductivity of liquid Fe70C30 with 8.4 wt % carbon show a low thermal conductivity of 38 Wm−1 K−1 at the pressure‐temperature conditions of the topmost outer core. The corresponding heat flow of 6 TW at the core‐mantle boundary is notably lower than previous electrical resistivity results on Fe and Fe alloys. The alloying effect of carbon on the electrical and thermal conductivity of iron can thus play a significant role in understanding the heat flux at the core‐mantle boundary and the thermal evolution of the core.

Imaging Bulk and Edge Transport near the Dirac Point in Graphene Moiré Superlattices.

Van der Waals structures formed by aligning monolayer graphene with insulating layers of hexagonal boron nitride exhibit a moiré superlattice that is expected to break sublattice symmetry. Despite an energy gap of several tens of millielectronvolts opening in the Dirac spectrum, electrical resistivity remains lower than expected at low temperature and varies between devices. While subgap states are likely to play a role in this behavior, their precise nature is unclear. We present a scanning gate microscopy study of moiré superlattice devices with comparable activation energy but with different charge disorder levels. In the device with higher charge impurity (∼1010 cm-2) and lower resistivity (∼10 kΩ) at the Dirac point we observe current flow along the graphene edges. Combined with simulations, our measurements suggest that enhanced edge doping is responsible for this effect. In addition, a device with low charge impurity (∼109 cm-2) and higher resistivity (∼100 kΩ) shows subgap states in the bulk, consistent with the absence of shunting by edge currents.

Disorder dependence electron phonon scattering rate of V82Pd18 − xFex alloys at low temperature

We have systematically investigated the disorder dependence electron phonon scattering rate in three dimensional disordered V82Pd18−xFex alloys. A minimum in temperature dependence resistivity curve has been observed at low temperature T=Tm. In the temperature range 5 K≤T≤Tm the resistivity correction follows ρo5/2T1/2 law. The dephasing scattering time has been calculated from analysis of magnetoresistivity by weak localization theory. The electron dephasing time is dominated by electron–phonon scattering and follows anomalous temperature (T) and disorder (ρ0) dependence behaviour like τe-ph−1∝T2/ρ0, where ρ0 is the impurity resistivity. The magnitude of the saturated dephasing scattering time (τ0) at zero temperature decreases with increasing disorder of the samples. Such anomalous behaviour of dephasing scattering rate is still unresolved.

The influence of sulfur on the electrical resistivity of hcp iron: Implications for the core conductivity of Mars and Earth

AbstractCosmochemical and geochemical studies suggest sulfur (S) as a light alloying element in the iron‐rich cores of telluric planets, but there is no report of sulfur's alloying effect on the electrical and thermal transport properties of iron (Fe); a subject that is closely related to the dynamo action and thermal evolution of planetary cores. We measured the electrical resistivity of hexagonal‐closed‐packed (hcp) structured Fe alloy containing 3 wt. % silicon (Si) and 3 wt. % S up to 110 GPa at 300 K. Combined with the reported resistivities of hcp Fe and hcp Fe‐Si alloy, we determined the impurity resistivity of S in a hcp Fe matrix at high pressures. The obtained impurity resistivity of S is found to be smaller than that of Si. Therefore, S is a weaker influence on the conductivity of Fe alloy, even if S is a major light element in the planetary cores.

Electrical resistivity of substitutionally disordered hcp Fe–Si and Fe–Ni alloys: Chemically-induced resistivity saturation in the Earth's core

The thermal conductivity of the Earth's core can be estimated from its electrical resistivity via the Wiedemann–Franz law. However, previously reported resistivity values are rather scattered, mainly due to the lack of knowledge with regard to resistivity saturation (violations of the Bloch–Grüneisen law and the Matthiessen's rule). Here we conducted high-pressure experiments and first-principles calculations in order to clarify the relationship between the resistivity saturation and the impurity resistivity of substitutional silicon in hexagonal-close-packed (hcp) iron. We measured the electrical resistivity of Fe–Si alloys (iron with 1, 2, 4, 6.5, and 9 wt.% silicon) using four-terminal method in a diamond-anvil cell up to 90 GPa at 300 K. We also computed the electronic band structure of substitutionally disordered hcp Fe–Si and Fe–Ni alloy systems by means of Korringa–Kohn–Rostoker method with coherent potential approximation (KKR-CPA). The electrical resistivity was then calculated from the Kubo–Greenwood formula. These experimental and theoretical results show excellent agreement with each other, and the first principles results show the saturation behavior at high silicon concentration. We further calculated the resistivity of Fe–Ni–Si ternary alloys and found the violation of the Matthiessen's rule as a consequence of the resistivity saturation. Such resistivity saturation has important implications for core dynamics. The saturation effect places the upper limit of the resistivity, resulting in that the total resistivity value has almost no temperature dependence. As a consequence, the core thermal conductivity has a lower bound and exhibits a linear temperature dependence. We predict the electrical resistivity at the top of the Earth's core to be 1.12×10−6Ωm, which corresponds to the thermal conductivity of 87.1 W/m/K. Such high thermal conductivity suggests high isentropic heat flow, leading to young inner core age (<0.85 Gyr old) and high initial core temperature. It also strongly suppresses thermal convection in the core, which results in no convective motion in inner core and possibly thermally stratified layer in the outer core.