High Temperature Electrical Conductivity Research Articles

Sandwich-structured polymer dielectrics exhibiting significantly improved capacitive performance at high temperatures by roll-to-roll physical vapor deposition

Electrostatic capacitors with ultrahigh power density are the key components in modern electrical and electronic systems. Polymers are preferred dielectrics for high-voltage electrostatic capacitors, however, unable to meet the ever-growing high-temperature requirements in emerging applications, such as electric vehicles, and photovoltaic power generation. In this work, sandwich-structured Polyphenylene sulfide (PPS) films with Al2O3 as the coating layer have been prepared by using roll-to-roll magnetron sputtering. The incorporation of Al2O3 coating layers enhances the potential barrier height at the electrode/dielectric interface, thereby impeding charge injection from electrodes and suppressing high-temperature electrical conduction. Consequently, the sandwich-structured PPS films demonstrate significantly improved breakdown strengths and enhanced capacitive performance at elevated temperatures compared to neat PPS films. The roll-to-roll magnetron sputtering process employed in fabricating these sandwich-structured dielectric films is highly compatible with large-scale capacitor film production. Thus, sandwich-structured PPS films hold promise in addressing the challenge of scalable fabrication of high-performance, high-quality polymer films required for high-temperature capacitive energy storage.

Intrinsic and extrinsic dielectric response of Sr0.95Nd0.05Fe12O19 nanoceramics doped with Sc3+ and Al3+ ions

ABSTRACT The dielectric response of M-hexaferrite nanoceramics is complex since it is determined by crystal structure and microstructure. We studied the dielectric behavior of Nd3+ modified Sr2 + Fe12O19 nanoceramics with ferric ions, responsible for magnetic properties, substituted by Sc3+ and Al3+. To compare the effect of different ionic radii we discussed the dielectric response of Sr0.95Nd0.05Fe12-xScxO19 and Sr0.95Nd0.05Fe12-xAlxO19 at the doping level of x = 1.08. The dielectric response was found to consist of four contributions: (i) Low-temperature dispersion of dielectric polarization created by doping-induced spin-canting. The polarization, described by the inverse Dzyaloshinskii-Moriya model, is in nanoceramics limited by the shape and size of the crystallites. (ii) Changes in relaxation modes of polar vacancies due to interaction with electric dipole moments modified by deformation of oxygen octahedra. (iii) Dielectric dispersion in room temperature range related to space charge relaxation in grain boundaries. (iv) High-temperature electric conductivity of the grain interiors.

Exploring the impact of multivalent substitution on high-temperature electrical conductivity in doped lanthanum chromite perovskites: An experimental and ab-initio study

Doped LaCrO3 perovskites hold promise as robust materials for electrical interconnects and sensor applications in harsh environments. In this work, we investigated the high-temperature behavior of La1–xSrxCrO3, La1–xCaxCrO3 and La0.8Sr0.2Cr1-x MnxO3 (0.1 ≤ x ≤ 0.4) through a combination of computational modeling and physical characterization up to 1500 °C. Crystalline structural properties were determined and compared with ab-initio calculations, which demonstrated excellent agreement with experimental findings. High-temperature electrical conductivity measurements were performed under different atmospheres. Calcium and strontium/manganese co-doped lanthanum chromites exhibited typical semiconductor exponential trends and conductivity showed proportional correlation with substitutions levels up to 30%. The DFT modelling was completed up to 1500 °C, including low and high temperature chromite phases and oxygen vacancies insertion. Calculations were correlated with experimental electrical properties. This work expands the understanding of doped lanthanum chromites and paves the way for the development of materials suitable for demanding high-temperature applications.

Design and competitive growth of different spinels at 750 °C for the multi-component CuCoMnFe alloy coatings

The diversified MnCoCuFe coatings can enhance the thermal growth stability and sintering property of spinel, and the multicomponent spinel exhibits good high temperature conductivity. The oxidation products of seven composite alloy coatings at 750 °C, CoNi(Fe), CoMn(Fe), CoMnCu(Fe), MnCu(Fe), MnCuCo(Fe), CuCoMn(Fe) and CuCo(Fe) coatings, were discussed in details. Due to differences in the elements and their concentrations in the designed coatings, some coatings could produce spinel, while others did not. The designed CuCo(Fe) coating and CuCoMn(Fe) coating prepared by electrodeposition in this study with the concentration ratio approximately nCu:nCo:nMn≈1:1:1. The oxidation reaction equations for the CuCoMnFe coating and CuCoFe coating at 750 °C were discussed. CoFe2O4 spinel was preferentially formed in the CuCoFe coating and CuMn2O4 spinel was preferentially formed in the CuCoMnFe coating. Both coatings demonstrated the good high-temperature oxidation resistance and high-temperature electrical conductivity.

Rhenium in the Earth's Crust: A Comprehensive Review of Mineralogy, Geochemistry and Economic Significance

Rhenium, a unique and valuable metal with exceptional properties which is vital in various industrial applications, primarily found in conjunction with minerals like molybdenite and chalcopyrite, predominantly in western countries. Despite its rarity, understanding its geological distribution, geochemical characteristics, atomic structure, and behavior is essential. This paper provides a concise overview of the geological and geographical occurrences of rhenium, shedding light on its formation within both igneous and sedimentary environments. Additionally, it examines its economic significance, emphasizing its critical role in industries like aerospace, electronics, and petrochemicals due to its high-temperature resistance, corrosion resistance, and electrical conductivity enhancement. This comprehensive exploration highlights the importance of rhenium as a byproduct of mining, contributing significantly to technological advancements and innovation across various sectors.

Features of electrical conductivity at high temperatures of complex titanomagnetite ores from the Gusevogorsky deposit

Relevance is determined by the search and selection of the most information-intensive characteristics and physical properties of complex titanomagnetite ores in connection with the need for scientifically based criteria for their detection, quality assessment during selective mining and selection of optimal enrichment technology. Research methodology. To study the electrical properties, samples in the shape of a cube with an edge of 0.02 m were used. The measurements were carried out in an open system at atmospheric pressure. Electrical resistance was measured with a two-electrode setup every 10 degrees in the temperature range 20–800 ºC. Heating rate 0.066 deg/s. The measuring device is an E6-13 teraohmmeter with a dynamic range from 10 to 1014 Ohms and a relative measurement error from ±2.5% to 4% at the end of the range. Results. A collection of samples of complex titanomagnetite ores from the Gusevogorsky deposit (Northern quarry) was studied using physical, mineralogical and petrographic methods. Functional connections have been established between the electrical parameters of high-temperature electrical conductivity (Eₒ – activation energy, lg Rₒ – the so-called electrical resistance coefficient), the value and nature of the electrical resistance lg R in the temperature range 20−800 °C of the studied samples of complex ores with their structural and textural features and mineral composition. Based on structural and textural features, mineral composition and electrical parameters, the studied samples are clearly divided into three groups. Conclusions. The presented results, in combination with other physicochemical parameters, can be used as a reliable indicator of rapid assessment of the material being studied. Significant differences in the electrical parameters of titanomagnetite ores provide additional information about their quality. In combination with other methods, we hope for the possibility of using these parameters in the selective extraction of ores that require different enrichment regimes.

LaBa2Fe3O8 cubic perovskite; oxygen-nonstoichiometry defects and conductivity

Point defects behind nonstoichiometry of the highly oxygen-vacant LaBa2FeIII3O8 single-perovskite structure are studied by quenching a set of nine samples close to FeIII from equilibria at two partial pressures of oxygen, pO2, at four temperatures T. This supports a simplified defect model that fits well the high-temperature electrical conductivity around and below the FeIII point, while deviating somewhat in the oxidized range. The conductivity fitted by sum of its electronic and ionic components versus T and pO2 in the surrounding gas reveals a good oxygen-ionic conductor. Oxygen diffusion behind conductivity transients upon a pO2 change is discussed.

The formation of spinel CuxMn3-xO4 at 750 °C in the designed CuMn layers for solid oxide fuel cell applications

The Cu-Mn based spinel coatings without Cr show good application prospects due to their high conductivity and thermal expansion coefficient matching with metallic interconnectors. Based on the Cu-Mn-O phase diagram, the CuMn alloy layers with different Cu/Mn ratios were designed by electro-deposition and high energy micro-arc alloying (HEMAA) processes. The Mn-33Cu-17Co layer was prepared by HEMAA for thermal growth of the CuMn spinel oxides, and the fine-grained 430 layer was prepared by HEMAA as an interlayer at the interface between the 430 SS substrate and the coating. The microstructure and composition of the composite layers were analyzed. The results show that after oxidation treatment at 750 °C for 500 h, the oxide products of the Mn-33Cu-17Co layer were mainly cubic spinel Cu1.4Mn1.6O4 and CuO, which were different from those of the Mn-35Cu oxide layer, spinel Cu1.2Mn1.8O4 and Mn2O3. The aggregation of Cu-rich oxides was not found in the cross-section and on the top surface of the Mn-33Cu-17Co oxide layer, and the outer spinel layer was uniform and compact. The designed Mn-33Cu-17Co layers, Mn-35Cu layers and Mn1.5Cu1.5 layers showed good high temperature oxidation resistance and electrical conductivity.

Fast grain growth phenomenon in high-entropy ceramics: A case study in rare-earth hexaaluminates

It is generally reported that the grain growth in high-entropy ceramics at high temperatures is relatively slower than that in the corresponding single-component ceramics owing to the so-called sluggish diffusion effect. In this study, we report a fast grain growth phenomenon in the high-entropy ceramics (La_0.2Nd_0.2Sm_0.2Eu_0.2Gd_0.2)MgAl₁₁O₁₉ (HEMA) prepared by a conventional solid-state reaction method. The results demonstrate that the grain sizes of the as-sintered HEMA ceramics are larger than those of the corresponding five single-component ceramics prepared by the same pressureless sintering process, and the grain growth rate of HEMA ceramics is obviously higher than those of the five single-component ceramics during the subsequent heat treatment. Such fast grain growth phenomenon indicates that the sluggish diffusion effect cannot dominate the grain growth behavior of the current high-entropy ceramics. The X-ray photoelectron spectroscopy (XPS) analysis reveals that there are more oxygen vacancies (O_V) in the high-entropy ceramics than those in the single-component ceramics owing to the variable valance states of Eu ion. The high-temperature electrical conductivities of the HEMA ceramics support this analysis. It is considered that the high concentration of O_V and its high mobility in HEMA ceramics contribute to the accelerated migration and diffusion of cations and consequently increase the grain growth rate. Based on this study, it is believed that multiple intrinsic factors for the high-entropy ceramic system will simultaneously determine the grain growth behavior at high temperatures.

Electrical parameters of high-temperature electrical conductivity, frequency characteristics of active electrical resistance and dielectric losses of samples of minerals, rocks, ores as a function of their composition and genesis

Relevance is determined by the search and selection of the most information-intensive characteristics and physical properties of minerals and rocks for the reconstruction of genesis conditions, as well as the need for scientifically based criteria for the detection of various minerals, their quality assessment, which is especially important in selective mining and the choice of the optimal ore dressing technology. Research methodology. Для исследования электрических свойств были использованы образцы в форме кубика с ребром 0,02 м. To study the electrical properties, samples in the form of a cube with an edge of 0.02 m were used. The measurements were performed in an open system at atmospheric pressure. The electrical resistance was measured with two-electrode setup every 10 degrees in the temperature range of 20–900 ºC. The heating rate is 0.066 deg/s. Measuring instrument – E6-13 teraohmmeter with dynamic range from 10 to 1014 Ohm and relative measurement error from ±2.5 to 4% at the end of the range. The frequency dispersion of the active resistance and the dielectric loss tangent was studied at room temperature in the range of 0.01–100 kHz. The measuring device is the LCR-819 immitance meter. The technique is described in the instruction manual for the device (LCR-819 immittance meter. Operation manual. M., 2005. 26 p.). Results. Physical, physicochemical, mineralogical and petrographic methods have been used to study samples of some minerals, rocks, ores from different deposits of the Urals. Functional relationships are revealed between the electrical parameters of high-temperature electrical conductivity (activation energy E0 , the so-called electrical resistance coefficient lg R0 ), frequency characteristics of active resistance, dielectric loss tangent of the studied samples of minerals, rocks, ores with their genetic features, mineral composition and quality. The materials presented in the work are the result of many years of research by the author. Conclusions. The given results in combination with other physicochemical parameters can be used as a reliable indicator of the rapid assessment of the studied material.

Correction to: Study of high temperature electrical conductivity and thermoelectric performance in Mg2-δSi0.35-xSn0.65Gex (δ = 0–0.04 and x = 0, 0.05) intermetallic alloys

Correction to: Study of high temperature electrical conductivity and thermoelectric performance in Mg2-δSi0.35-xSn0.65Gex (δ = 0–0.04 and x = 0, 0.05) intermetallic alloys

Structure and Electrical Properties of Carbon-Rich Polymer Derived Silicon Carbonitride (SiCN)

This article reports on the structure and electronic properties of carbon-rich polysilazane polymer-derived silicon carbonitride (C/SiCN) corresponding to pyrolysis temperatures between 1100 and 1600 °C in an argon atmosphere. Raman spectroscopy, X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX), Scanning Electron Microscopy (SEM) and Hall measurements were used to support the structural and electronic properties characterization of the prepared C/SiCN nanocomposites. A structural analysis using Raman spectroscopy showed the evolution of sp2 hybridized carbon phase that resulted from the growth in the lateral crystallite size (La), average continuous graphene length including tortuosity (Leq) and inter-defects distance (LD) with an increase in pyrolysis temperature. The prepared C/SiCN monoliths showed a record high room temperature (RT) electrical conductivity of 9.6 S/cm for the sample prepared at 1600 °C. The electronic properties of the nanocomposites determined using Hall measurement revealed an anomalous change in the predominant charge carriers from n-type in the samples pyrolyzed at 1100 °C to predominantly p-type in the samples prepared at 1400 and 1600 °C. According to this outcome, tailor-made carbon-rich SiCN polymer-derived ceramics could be developed to produce n-type and p-type semiconductors for development of the next generation of electronic systems for applications in extreme temperature environments.

High-temperature electrical conductivity and electrochemical activity in oxygen redox reaction of La-doped Sr2FeCo0.5Mo0.5O6-δ

High-temperature electrical conductivity and electrochemical activity in oxygen redox reaction of La-doped Sr2FeCo0.5Mo0.5O6-δ

Trends in the Behavior of Point Defects in MB and MAB Phases

Binary and ternary transition metal borides exhibit many outstanding properties, such as high melting temperature, high temperature strength, and electrical and thermal conductivities. However, defect properties have been rarely studied so far. Here, using first-principles calculations, we investigate structural effects on defect recovery processes in MB and MAB phases focusing on how Al layers and the type of transition metal affect annihilation of defects. First, we find that metal interstitials cannot be accommodated in MAB phases that have two Al layers, but instead they form antisites, which are largely immobile and therefore detrimental for defect recovery processes. We also find that the absence of Al layers in MB phases that have B chains leads to faster migration of metal interstitials and lower recombination barriers of B Frenkel pairs and hence contributes to efficient defect recovery processes of those MB phases as compared to the corresponding MAB phases. In the other types of MB and MAB phases that have B rings, we find that the role of Al layers varies depending on the type of metal elements. Lastly, we find that a larger M–B bond strength, which depends on the type of transition metal in MAB phases, correlates with a higher recombination barrier of B Frenkel pairs. Based on the discovered trends, we provide insights into the selection of materials to help design diverse applications where defect recovery processes are important.

Study of high-temperature electrical conductivity and thermoelectric performance in Mg2−δSi0.35−xSn0.65Gex (δ = 0–0.04 and x = 0, 0.05) intermetallic alloys

Study of high-temperature electrical conductivity and thermoelectric performance in Mg2−δSi0.35−xSn0.65Gex (δ = 0–0.04 and x = 0, 0.05) intermetallic alloys

Persistent Cyanobacteria Blooms in Artificial Water Bodies-An Effect of Environmental Conditions or the Result of Anthropogenic Change.

Algal blooms are an emerging problem. The massive development of phytoplankton is driven partly by the anthropogenic eutrophication of aquatic ecosystems and the expansion of toxic cyanobacteria in planktonic communities in temperate climate zones by the continual increase in global temperature. Cyanobacterial harmful algal blooms (CyanoHABs) not only disturb the ecological balance of the ecosystem, but they also prevent the use of waterbodies by humans. This study examines the cause of an unusual, persistent bloom in a recreational, flow-through reservoir; the findings emphasize the role played by the river supplying the reservoir in the formation of its massive cyanobacterial bloom. Comprehensive ecosystem-based environmental studies were performed, including climate change investigation, hydrochemical analysis, and bio-assessment of the ecological state of the river/reservoir, together with monitoring the cyanobacteria content of phytoplankton. Our findings show that the persistent and dominant biomass of Microcystis was related to the N/P ratio, while the presence of Aphanizomenon and Dolichospermum was associated with the high-temperature end electric conductivity of water. Together with the increase in global temperature, the massive and persistent cyanobacterial bloom appears to be maintained by the inflow of biogenic compounds carried by the river and the high electric conductivity of water. Even at the beginning of the phenomenon, the reservoir water already contained cyanobacterial toxins, which excluded its recreational use for about half the year.

COMPARATIVE STUDIES OF EDM PROCESS CONDUCTIVE LAYER ON SILICON NITRIDE WITH BRASS AND COPPER ELECTRODES

Insulating materials are now subjected to precision electrical discharge machining (EDM) using an assisting electrode method (AEM). The electrode materials usually comprise copper, graphite and copper alloys that have high melting temperature and excellent electrical and thermal conductivity. A brass electrode is known as a humble electrode. Performances of brass and copper pipe electrodes were compared on silicon nitride machining. Results showed that a brass electrode had more advantages than a copper electrode. Material removal rate (MRR), electrode wear ratio (EWR) and surface roughness were compared, while the conductive layers were examined by a scanning electron microscope (SEM) energy dispersive spectrometer (EDS).

High-temperature electrical properties of polymer-derived ceramic SiBCN thin films fabricated by direct writing

The in situ temperature monitoring of hot components in harsh environments remains a challenging task. In this study, SiBCN thin-film resistance grids with thicknesses of 1.8 μm were fabricated on alumina substrates via direct writing. Owing to their dense microscopic morphology and extremely high graphitisation level, the produced SiBCN films exhibited large high-temperature oxidation resistance and electrical conductivity. The resistance–temperature, stability, and repeatability characteristics of these films were examined in an aerobic environment at temperatures up to 800 °C. The obtained results revealed that the thermistor resistance decreased monotonously with increasing temperature from room temperature to 800 °C. The SiBCN film resistance variations observed during repeated temperature cycling in the regions of 505–620 °C and 610–720 °C were 0.09% and 1.7%, respectively. The high cyclability and stability of the SiBCN thin film thermistor suggested its potential applicability for the in situ temperature monitoring of hot components in harsh environments.

Enhancement of thermoelectric properties of low-toxic and earth-abundant copper selenide thermoelectric material by microwave annealing

Our current work aims to enhance the thermoelectric properties of p-type copper selenide (Cu2Se), a low toxic, earth-abundant intermediate material for thermoelectric applications by a low-cost, simple and fast microwave-assisted metallurgy route. Hot pressed copper selenide pellets were treated at various temperatures in the range of 250 oC to 425 oC in a microwave furnace. We analyze the variation of several characteristics of the samples, such as electrical, thermal, structural, microscopic, dielectric, and mechanical properties, when the samples are exposed to different annealing conditions. Broadband dielectric spectroscopy (BDS) analysis facilitated the comprehensive study of variation of AC electrical characteristics of the samples such as AC conductivity, dielectric permittivity storage, dielectric loss, and AC capacitance, with temperature and frequency. The results indicate exceptional electrical, thermal, and mechanical properties for samples annealed at 375 oC with high room temperature electrical conductivity of 538.3 S/cm and ultra-low thermal conductivity of 0.59 W/mK. The crystallinity improved as the annealing temperature increased, as did the formation of oxides over 400 oC. The samples have a high strength with maximum nanohardnesss and compression strength of 3.75 GPa and 326.75 MPa, respectively that has been a significant improvement over the existing studies on copper selenides.

Tailoring high-temperature stability and electrical conductivity of high entropy lanthanum manganite for solid oxide fuel cell cathodes

Optimum (La0.2Nd0.2Sm0.2Ca0.2Sr0.2)MnO3 exhibits excellent high-temperature resistance to elemental segregation and chemical compatibility with 8YSZ while maintaining good electrical conductivity.