Ferromagnetism of manganese-doped InSb alloys

InSb samples containing 0.22–1.42 wt % manganese were synthesized and identified. The unit cell parameter decreased as the manganese concentration increased. The samples contained microinclusions of manganese antimonides. Electrical and magnetic measurements showed two ferromagnetic phases (In_1?x Mn_xSb solid solution with T _c ～ 7 K and MnSb with T _c ～ 580 K) and a ferrimagnetic phase (Mn₂Sb). The samples had p-type conductivity with a charge carrier concentration of about 10²⁰cm^?3. The semiconductor conductivity was observed at low temperatures and changed to the metal conductivity with temperature elevation.     

Phase equilibria and electrical and magnetic properties of a eutectic in the GaSb-MnSb system

A set of physicochemical analysis methods showed that GaSb and MnSb form a eutectic at 41 mol % MnSb and T _melt = 632°C. The eutectic is of the platelet type and has metallic conduction. The eutectic GaSb + MnSb is a composite ferromagnetic with a Curie temperature of ～600 K. The behavior of the electrical resistance in a magnetic field is complex. At low magnetic fields up to 0.8 T, the resistance abruptly drops, and at high magnetic fields, it slowly increases. Such behavior occurs both at low temperatures (5 K) and at 300 K. The change of the trend in the resistance takes place at the magnetic field at which there is magnetization saturation in the magnetic field dependences. Such a dependence of the resistance on the magnetic field is explained by a change of the mechanism of scattering of charge carriers.     

Thermal and electronic charge transport in bulk nanostructured Zr0.25Hf0.75NiSn composites with full-Heusler inclusions

Bulk Zr_0.25Hf₀₇₅NiSn half-Heusler (HH) nanocomposites containing various mole fractions of full-Heusler (FH) inclusions were prepared by solid state reaction of pre-synthesized HH alloy with elemental Ni at 1073 K. The microstructures of spark plasma sintered specimens of the HH/FH nanocomposites were investigated using transmission electron microscopy and their thermoelectric properties were measured from 300 K to 775 K. The formation of coherent FH inclusions into the HH matrix arises from solid-state Ni diffusion into vacant sites of the HH structure. HH(1–y)/FH(y) composites with mole fraction of FH inclusions below the percolation threshold, y∼0.2, show increased electrical conductivity, reduced Seebeck coefficient and increased total thermal conductivity arising from gradual increase in the carrier concentration for composites. A drastic reduction (∼55%) in κ_l was observed for the composite with y=0.6 and is attributed to enhanced phonon scattering due to mass fluctuations between FH and HH, and high density of HH/FH interfaces.     

Synthesis, Phase Diagram, and Conductivity Study in a La0.5+x+yLi0.5−3xTi1−3yMn3yO3System

The stoichiometry, polymorphysm, and electrical behaviour of solid solutions of La_0.5+y+xLi_0.5−3xTi_1−3yMn_3yO₃with perovskite-type structure have been studied. Data are given in the form of a solid solution triangle, phase diagrams, XRD patterns for the three polymorphs, A,β, and C, composition-dependence of their lattice parameters, and ionic and electronic conductivity plots. Microstruture and composition were studied by SEM/EDS and electron probe microanalysis. These compounds are mixed conductors. Ionic conductivity decreases when the amount of lithium diminishes and electronic conductivity increases with manganese content.     

Electrical conductivity and dielectric constant measurements of liquid crystal–gold nanoparticle composites

The behaviour of the anisotropic electrical conductivity of liquid crystal–gold nanoparticle (LC‐GNP) composites consisting of a commercially available room temperature nematic compound doped with alkylthiol‐capped GNPs has been investigated. The nematic–isotropic transition of the composite decreases nearly linearly with increasing X, the concentration of GNP (in weight %) at a rate of about 1°C /weight %. The inclusion of GNPs increases the electrical conductivity of the system with the value increasing by more than two orders of magnitude for X = 5%. However, the anisotropy in conductivity, defined as the ratio of the conductivity along (σ_∥) and orthogonal (σ_⊥) to the director shows a much smaller but definite decrease as X increases.     

Remarkable Oxygen‐Evolution Activity of a Perovskite Oxide from the Ca2−xSrxFe2O6−δ Series

Herein in we report the unprecedented catalytic activity of an iron‐based oxygen‐deficient perovskite for the oxygen‐evolution reaction (OER). The systematic trends in OER activity as a function of composition, defect‐order, and electrical conductivity have been demonstrated, leading to a methodical increase in OER catalytic activity: Ca₂Fe₂O_6?δ<CaSrFe₂O_6?δ<Sr₂Fe₂O_6?δ. Sr₂Fe₂O_6?δ also has the highest electrical conductivity and a unique type of defect‐order. In conventional experiments using glassy carbon electrode, Sr₂Fe₂O_6?δ shows better OER activity than the current state of the art catalysts, Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3?δ and RuO₂. It also offers a high intrinsic electrical conductivity, which allows it to act as a catalyst without the need for glassy carbon electrode or carbon powder. Pure disks of this material exhibit an outstanding activity for OER, without any additives or need for electrode preparation.     

A study of TiO system between Ti3O5 and TiO2 at high temperature by means of electrical resistivity

The TiO system between the compositions TiO₂ and Ti₃O₅ has been studied in following the electrical conductivity against the oxygen partial pressure. Several features are discussed : the dependence of electrical conductivity versus oxygen pressure, the kinetics of approach to equilibrium, and reversibility during oxidation and reduction paths. The results suggest an important contribution of point defects for small departures from the composition TiO₂ at high temperature.     

ELECTRICAL CONDUCTIVITY OF IODINE DOPED POLY(PHTHALOCYANINATOSILOXANE)/PPTA BLEND FIBERS

Poly(phthalocyaninatosiloxane), [Si(Pc)O]n, with the number average degree of polymerization of about 130 was prepared by heating its monomer Si(Pc) (OH)_2, in solid state at 420℃for 42 hrs at 10~(-3) torr dynamic vacuum. The [Si(Pc)O]n powder was iodine doped with I_2-bensene solution for 48 hrs. Pure iodine doped poly(phthalocyaninatosiloxune), {[Si(Pc)O]I_y}n, fibers and {[Si(Pc)O]I_y}n/poly(p-pbenylene terephthalamide) blend fibers were wet-spun with dry nltrogen-sealed Teflon lined device. D.C. electrical conductivity of the fibers was measured by the four-probe method with an automated charge transport measurement system from 80K to room temperature. It was found that the dependence of conductivity, σ, on temperature, T, could fit a group of thermal fluctuation-induced tunnelling (TFIT) equations, and that the dependence of conductivity on volume fraction, φ, of the iodine doped {[Si(Pc)O]I_y}n could fit a group of modified percolation equations. A thrce-dimensioual composite plot of σ-1 / T-φshows that these two groups of equations match each other quite well. It has been pointed out that for the blend fibers their composition is the most important factor for both mechanical and electrical properties.     

Electrical conductivity and interactions in poly(methyl methacrylate)-1-butyl-3-methylimidazolium hexafluorophosphate microheterogeneous system

Microheterogeneous composite films of varied composition based on poly(methyl methacrylate) and 1-butyl-3-methylimidazoluim hexafluorophosphate have been prepared. The introduction of N-vinylpyrrolidone into the polymer matrix has been shown to deteriorate the electrical conductivity of the composite. Specific ionic conductivity of the composites has been measured as a function of the alternate current frequency and the material composition. Hydrogen bonding between the polymer electrolyte components as well as additional interaction between cation and anion of the ionic liquid encapsulated in the polymer matrix have been confirmed by IR spectroscopy studies.

     

Hole-phonon Scattering and Thermal Conductivity of p-type InSb from 2 to 100 K

The hole-phonon interaction contributing to the thermal conductivity of three p-type samples of InSb is analyzed between temperatures of 2 and 100 K. In addition to the phonon scattering by bound and free holes, other phonon scattering such as boundary, point defect and phonons are considered. Both relaxation rates for q≤2k _F and for q>2k _F are used for free hole-phonon scattering. The role of screening due to plasma on hole-phonon scattering is also included. The Callaway model for thermal conductivity is utilized from which an excellent fit to the experimental data is obtained over the whole temperature range. This revised version was published online in August 2006 with corrections to the Cover Date.     

Electrical conductivity of the oxygen-deficient rutile CrNbO4−δ

Reduction of CrNbO₄ under 5% H₂/Ar at different temperatures has been carried out to obtain oxygen-deficient rutiles aiming for mixed ionic and electronic conductivities. Decomposition is observed at temperatures above 950 °C. Hence, the more reduced rutile that could be obtained corresponds to that obtained at 950 °C which has the composition CrNbO_3.96. When compared with CrNbO₄, the reduced product exhibits an electrical conductivity between three and four orders of magnitude higher. Both bulk and grain boundary conductivities are enhanced upon reduction. The small amount of vacancies generated by reduction does not induce oxygen conductivity. However, the presence of the corresponding small amount of Nb(IV) in the rutile affects strongly the electrical properties. This is likely related to the structural characteristics of rutile that allow for strong Nb–Nb interactions. On the other hand, no evidence of protonic conductivity has been found.     

Highly Conductive MXene Film Actuator Based on Moisture Gradients

MXene (Ti₃C₂T_x) is a new 2D material with both hydrophilicity and high electrical conductivity, and it has shown promise in smart electronic devices. Reported herein is a homogeneous MXene film actuator with high electrical conductivity triggered by moisture gradients. The actuator is highly sensitive to moisture and undergoes deformation, with the maximum bending angle as high as 155° at a relative humidity difference of 65 %. Several analysis methods show that the humidity drive and large deformation of the MXene film occur in situ by asymmetric expansion of the bilayer structure. The combination of deformation and electrical conductivity makes this film applicable to flexible excavators, electrical switches, and other fields, applications that are difficult to achieve directly by using other 2D materials. More importantly, this work further expands the new application range of MXene materials and provides new opportunities for building the next generation of high‐conductivity smart actuators.     

Investigation of the change in the electronic properties of FeF3 by the introduction of oxygen using a molecular orbital method

FeF₃ has attracted interest as a conversion‐reaction‐based positive electrode material in applications to lithium ion batteries. However, slow reaction kinetics is a major drawback due to its poor electrical conductivity. The electronic features of FeF₃ were examined using the DV‐Xα molecular orbital method. This article reports the effects of oxygen doping on the bonding characteristics and electrical conductivity. An analysis of the bond overlap population and spatial distribution of electrons showed that the Fe? O bond has a more covalent nature than the Fe? F bond. New energy levels were generated in the original band gap region through an interaction between the Fe3d and O2p orbitals with the introduction of oxygen. The electrical conductivity of FeF₃ is expected to be increased by the partial substitution of oxygen for fluorine due to the higher covalent character and the formation of new energy levels. © 2013 Wiley Periodicals, Inc.     

Solid-state synthesis and characterization of Ca-substituted YAlO3 as electrolyte for solid oxide fuel cells

ABO₃-type oxides are recently being explored as solid electrolytes for solid oxide fuel cells. The objective of this work was to study an ABO₃-type perovskite oxide, YAlO_3, for its electrical properties and its suitability as a solid electrolyte. The undoped and doped compositions of Y_{1 - x}Ca_xAlO_{3 - d}( x = 0 - 0.25 ) {{\hbox{Y}}_{1 - x}}{\hbox{C}}{{\hbox{a}}_x}{\hbox{Al}}{{\hbox{O}}_{3 - \delta }}\left( {x = 0 - 0.25} \right) have been synthesized. The phase purity of the samples has been investigated by X-ray diffraction studies. The electrical conductivity studies have been performed using ac impedance spectroscopy in the range 200–800 °C in air. The doped YAlO₃ compositions exhibit a total conductivity of about 1 mS/cm at 800 °C. The microstructural evaluation of the samples has been conducted by scanning electron microscopy and energy dispersive spectrum analysis.     

High temperature X-ray diffraction studies of the crystallization process of thin amorphous films with the chemical composition CrSi2.57

The crystallization process of amorphous thin films with the chemical composition CrSi_2.57 has been investigated by means of high temperature X-ray diffractometry. The crystallization of the amorphous as-deposited films takes place in two stages; in the first stage CrSi₂ is formed and in the second Si, resulting in a two component nano-disperse structure. The results are in agreement with investigations of the thermopower and the electrical conductivity [5, 6].     

Die Anisotropie der elektrischen Leitfähigkeit im Mangan-Defektsilicid Mn27Si47

Single crystals of Mn₂₇Si₄₇ containing very little of MnSi inclusions have been measured with respect to the electrical conductivity parallel and perpendicular to thec-axis. An anisotropic behavior was observed, particularly at low temperatures. Mn₂₇Si₄₇ was found to be a p-type semiconductor in agreement with literature data on similar manganese defect disilicides.     

Solution properties of poly(styrene-co-sodium styrene sulfonate)

The relative conductivities of solutions of poly(styrene-co-sodium styrene sulfonate) (PSSNa) in N,N-dimethylformamide + water have been measured as functions of temperature and at various concentrations. With the aid of the newly proposed theory related to the effect of solute adsorption on the relative conductivity measurement, the experimental data were analysed, and some interesting parameters describing the interfacial properties were deduced. The concentration of PSSNa data dependence of the reduced electrical conductivities has been fitted to an equation similar to the Vogel–Tammann–Fulcher based on the critical concentration model. The intrinsic electrical conductivity of Vogel [σ_V], the critical concentration and the concentration of Vogel C_VFT were calculated. The behaviour of polymers close to interfaces has been studied with the parameter of [σ_V]. Two mechanisms of interaction between a polymer solution and a surface are in general distinguished, leading to the formation of adsorbed and grafted layers.     

High temperature X-ray diffraction studies of the crystallization process of thin amorphous films with the chemical composition CrSi2.57

The crystallization process of amorphous thin films with the chemical composition CrSi_2.57 has been investigated by means of high temperature X-ray diffractometry. The crystallization of the amorphous as-deposited films takes place in two stages; in the first stage CrSi₂ is formed and in the second Si, resulting in a two component nano-disperse structure. The results are in agreement with investigations of the thermopower and the electrical conductivity [5, 6].     

Theoretical Aspects on Doped-Zirconia for Solid Oxide Fuel Cells: from Structure to Conductivity

Solid oxide fuel cells (SOFCs) are regarded to be a key clean energy system to convert chemical energy (e.g. H₂ and O₂) into electrical energy with high efficiency, low carbon footprint, and fuel flexibility. The electrolyte, typically doped zirconia, is the "state of the heart" of the fuel cell technologies, determining the performance and the operating temperature of the overall cells. Yttria stabilized zirconia (YSZ) have been widely used in SOFC due to its excellent oxide ion conductivity at high temperature. The composition and temperature dependence of the conductivity has been hotly studied in experiment and, more recently, by theoretical simulations. The characterization of the atomic structure for the mixed oxide system with different compositions is the key for elucidating the conductivity behavior, which, however, is of great challenge to both experiment and theory. This review presents recent theoretical progress on the structure and conductivity of YSZ electrolyte. We compare different theoretical methods and their results, outlining the merits and deficiencies of the methods. We highlight the recent results achieved by using stochastic surface walking global optimization with global neural network potential (SSW-NN) method, which appear to agree with available experimental data. The advent of machine-learning atomic simulation provides an affordable, efficient and accurate way to understand the complex material phenomena as encountered in solid electrolyte. The future research directions for design better electrolytes are also discussed.     

Electrical conductivity of poly(ethylene terephthalate)/expanded graphite nanocomposites prepared by in situ polymerization

Nanocomposites based on poly(ethylene terephthalate) (PET) and expanded graphite (EG) have been prepared by in situ polymerization. Morphology of the nanocomposites has been examined by electronic microscopy. The relationship between the preparation method, morphology, and electrical conductivity was studied. Electronic microscopy images reveal that the nanocomposites exhibit well dispersed graphene platelets. The incorporation of EG to the PET results in a sharp insulator‐to‐conductor transition with a percolation threshold (?_c) as low as 0.05 wt %. An electrical conductivity of 10^?3 S/cm was achieved for 0.4 wt % of EG. The low percolation threshold and relatively high electrical conductivity are attributed to the high aspect ratio, large surface area, and uniform dispersion of the EG sheets in PET matrix. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012