Geometry of Contact Metal-Semimetal BiSb Influence on Their Voltwatt Sensitivity in MM Range

Contact phenomena's studying is one of the most important physics and solid state department that has great applied significance. All modern solid state electronics based on use contact phenomena's in various junctions- electron-hole, metal-semiconductor etc.In recent time the class of solid state as semimetal which typical representatives are bismuth, antimony and its alloys is rather good searched. Special interest is the current traverse through small area metal-semimetal contact processes in connection with such contact may be used for detecting HF signals and measuring of small levels continuous and pulse UHF power as in centimeter as in millimeter wave length range [1,2\. One of the main characteristic of electromagnetic radiation detectors based on metal-semimetal BiSb contact is volt-watt sensitivity.     

Unexpected low thermal conductivity and large power factor in Dirac semimetal Cd_3As_2

Thermoelectrics has long been considered as a promising way of power generation for the next decades. So far,extensive efforts have been devoted to the search of ideal thermoelectric materials, which require both high electrical conductivity and low thermal conductivity. Recently, the emerging Dirac semimetal Cd3As2, a three-dimensional analogue of graphene, has been reported to host ultra-high mobility and good electrical conductivity as metals. Here, we report the observation of unexpected low thermal conductivity in Cd3As2, one order of magnitude lower than the conventional metals or semimetals with a similar electrical conductivity, despite the semimetal band structure and high electron mobility. The power factor also reaches a large value of 1.58 m W·m-1·K-2at room temperature and remains non-saturated up to 400 K.Corroborating with the first-principles calculations, we find that the thermoelectric performance can be well-modulated by the carrier concentration in a wide range. This work demonstrates the Dirac semimetal Cd3As2 as a potential candidate of thermoelectric materials.     

Temperature dependence of the electric field gradient for111Cd in antimony

For the temperature dependence of the electric field gradient of¹¹¹Cd in the semimetal antimony the well knownT ^3/2 relationship is valid over a wide temperature range. The slope parameterB differs from that for^{121, 123}Sb in antimony by a factor of about 2.3.     

Metal-Monocrystal BiSb Point Contact Detector for MM Wave Range

The paper presents the experimental results on thermoelectric detectors with the metal-semimetal BiSb point contact in the 8-mm wave range. The volt-watt sensitivity and response rate have been determined.     

RESPONSE RATE AND NOISE CHARACTERISTICS OF A BiSb METAL-SEMIMETAL CONTACT THERMOELECTRIC DETECTOR FOR THE MILLIMETER WAVE RANGE

The paper considers analytical and experimental results on the relative noise temperature and the thermal time constant of thermoelectric detectors with a point BiSb metal-semimetal contact in the 8-mm wave range.     

Electrical and magnetic properties of semimetallic and semiconducting alloys of BiSb

Studies on electrical conductivity, thermoelectric power (t.e.p), Hall effect and diamagnetic susceptibility have been carried out on two inhomogeneous Bi-Sb alloys in the temperature range 100–300 K. Measurements have been confined to the plane perpendicular to the three-fold axis. Antimony impurity levels have been postulated to exist between the bands L_v and L_c. These levels together with the existing band structure of Bi-Sb alloys can explain the observed behaviour of both the alloys of which one is a semimetal and the other a semiconductor. The semiconductor-metal transitions induced by magnetic fields as observed earlier, could also be explained with the help of these antimony levels. The majority of the carriers in both the cases are holes. The different electronic parameters including density of carriers, mobility, nature of the charge carriers and effective masses for all the three bands have been calculated.     

Volt-Watt Sensitivity of Semimetal BiSb Film Thermocouple Sensors in the 8 mm Wavelength Range

The paper considers the experimental and analytical data on volt-watt characteristics of metal-semimetal BiSb film point contacts in 8 millimeter wavelength range. Analytical expressions have been obtained for the volt-watt sensitivity and the resistance of the metal-semimetal BiSb film point contacts. A thermoelectric millimeter wave range detector has been designed on the basis of the sensors; the performance is illustrated by experimentally determined volt-watt relations.     

Electrical resistivity of liquid Bi–Sb alloys

The electrical resistivities of liquid Bi–Sb alloys have been measured by DC four-probe method within Bi-rich composition through a wide temperature range. The distinct anomaly of a hump shape was observed on resistivity–temperature (ρndash;T) curves for liquid Bi–Sb alloys on heating at the relatively high temperatures. These anomalies have revealed the temperature-induced liquid–liquid phase transition in Bi–Sb melts. The DSC results for BiSb20wt% alloy further prove the existence of liquid–liquid transition. Measuring the ρ–T curves first on heating and then on cooling we have found that on cooling the ρ–T curve remained linear. It means that the postulated liquid–liquid transition may be irreversible.     

Change in the electrical resistance of the metallic composite material-steel contact under friction and electric current

The I–V characteristics of the sliding contact of metallic composites of grade 45 steel without a lubricant are presented. Steel-based composites are shown to increase the actual electric-contact area due to the appearance of electric discharges, which provide the main passage of an electric current with a density up to 300 A/cm². Copper-based composites cannot initiate electric-discharge conduction because of the fracture of the contact zone material at a current density higher than 50 A/cm². The electrical resistivity of the contact layer of metallic composites is calculated. It is found that, during friction with a high current density, the electrical resistivity of the contact layer approaches the electrical resistivity of graphite. It is experimentally shown that the actual electric-contact area can be increased by the introduction of a Pb-Sn melt into the friction zone and reaching a current density higher than 300 A/cm² in the contact.     

Thermoelectric Properties of the TlBiS<Subscript>2</Subscript>-PbS Alloys

High efficiency of thermoelectric conversion can be achieved by using materials with a high Seebeck coefficient, high electrical conductivity, and low thermal conductivity. Mass-difference-scattering of the phonons is one of the most effective way for reducing the thermal conductivity in bulk thermoelectric materials. Investigations of transport phenomena in (TlBiS₂)_1-x (2PbS)_x alloys system have shown that in solid solutions of the (A³B⁵C ₂ ⁶ )_1-x (2A⁴B⁶)_x type at cation substitution according to scheme 2A⁴⁽⁺²⁾ A ³⁽⁺¹⁾ + B⁵⁽⁺³⁾ occurs a strong decrease of the lattice thermal conductivity. In the vicinity of x = 0. 50 the lattice part of thermal conductivity of (TlBiS₂)_1-x (2PbS)_x alloys decreases down to 0. 26 W/mK, i. e., it approaches the theoretical minimum. As a result, the thermoelectric figure of merit for these alloys ( 25%) exceeds the respective value for lead sulfide at room temperature.     

Hybrid Dispersion Dirac Semimetal and Hybrid Weyl Phases in Luttinger Semimetals: A Dynamical Approach

It is shown that hybrid Dirac and Weyl semimetals can be realized in a 3D Luttinger semimetal with quadratic band touching (QBT). This is illustrated using a periodic kicking scheme. In particular, the focus is on a momentum-dependent driving (nonuniform driving) and the realization of various hybrid Dirac and Weyl semimetals is demonstrated. A unique hybrid dispersion Dirac semimetal with two nodes is identified, where one of the nodes is linear while the other is dispersed quadratically. Next, it is shown that by tilting QBT via periodic driving and in the presence of an external magnetic field, one can realize various single/double hybrid Weyl semimetals depending on the strength of external field. Finally, it is noted that in principle, phases that are found in this work can also be realized by employing the appropriate electronic interactions.     

Spin-Dependent Thermoelectric Transport in Cobalt-Based Heusler Alloys

Sitting at the intersection of spintronics and thermoelectricity, research investigating the coupling of thermoelectric, magnetic, and electrical transport properties in materials has recently found that the ferromagnetic Heusler alloys are the ideal testbeds. These materials have attracted a lot of attention due to their useful magnetotransport properties and the possibility of tailoring these properties by modifying their composition or producing heterostructures. With the diverse range of interesting phenomena in the Heusler alloys, ferromagnetic Heusler alloys are also ideal candidates for engineering spin caloritronic devices that can take advantage of the interplay of the physics of heat flow, magnetism, and electric potential. The fundamental physical concepts important to spin-dependent thermoelectrics research are introduced and recent studies of several ferromagnetic Heusler compounds are reviewed, highlighting some exceptional latest experiments on half-metallic Co₂TiSn and the ferromagnetic Weyl semimetal Co₂MnGa. Furthermore, the potential to generate useful magnetothermoelectric voltages in electronic devices based on the anomalous Nernst effect is discussed.     

Enhancement of the power factor of Pb1–xSnxTe (0.00 ≥ x ≥ 0.08) alloys

Thermoelectric properties of Pb_1–x Sn _x Te (0.00 ≥ x ≥ 0.08) alloys synthesized by melting-quenching-annealing method have been investigated. The sample structure and phases have been investigated by Raman spectroscopy and X-ray diffraction, while the morphology and stoichiometry have been studied by SEM and EDX. The nanomaterial exists in a single phase and has a face-centred cubic (fcc) lattice of rock-salt type in the whole range of x values in Pb_1–x Sn _x Te alloys. The effect of tin substitution on the lattice vibration and chemical bonding nature in the lead telluride has been investigated by Raman spectroscopy at room temperature. The Seebeck coefficient and electrical resistivity have been measured in the temperature range of 100–400 K. The electrical resistivity measurements reveal that the compounds have extrinsic to intrinsic conduction transition and the electrical temperature transition shifts to higher values with increasing the Sn content. For all studied compounds, the Seebeck coefficient is positive indicating predomination of positive charge carriers over the entire temperature range. The thermoelectric power factor was enhanced to 2.03 mWm^?1 K^?2 for the sample with 4% Sn content at room temperature.     

Effect of deformation on the electronic structure and topological properties of the A<Superscript>II</Superscript>Mg<Subscript>2</Subscript>Bi<Subscript>2</Subscript> (A<Superscript>II</Superscript> = Mg,Ca,Sr,Ba) compounds

The electronic structure and topological properties of the A^IIMg₂Bi₂ (A^II = Mg,Ca,Sr,Ba) compounds are theoretically studied with the use of exact exchange. It is found that the Mg₃Bi₂ compound in the equilibrium state is a semimetal, whereas three other compounds are semiconductors with a direct fundamental band gap. It is predicted that the uniaxial deformation of three-component compounds results in transitions to topologically nontrivial phases: topological insulator and topological and Dirac semimetals. Owing to such a rich variety of topologically nontrivial phases, these compounds may be of interest for further theoretical and experimental studies.     

Point-contact diodes

Point-contact diodes based either on the mechanism of electronic tunnelling through an insulating barrier or on the thermoelectric effect of hot carriers in heavily doped semiconductors are described. The requirements necessary for these devices to be used as harmonic generators and mixers in the 2–200 THz region are emphasized, and some new developments are reported. Outstanding characteristics of the devices which use either the semimetal antimony or the semiconductors SnTe or Bi₂Te₃ as a diode base are high detection sensitivity and high mechanical stability over long periods of use either as harmonic generators or as mixers.     

Topological nodal line semimetals predicted from first-principles calculations

Topological semimetals are newly discovered states of quantum matter, which have extended the concept of topological states from insulators to metals and attracted great research interest in recent years. In general, there are three kinds of topological semimetals, namely Dirac semimetals, Weyl semimetals, and nodal line semimetals. Nodal line semimetals can be considered as precursor states for other topological states. For example, starting from such nodal line states, the nodal line structure might evolve into Weyl points, convert into Dirac points, or become a topological insulator by introducing the spin–orbit coupling (SOC) or mass term. In this review paper, we introduce theoretical materials that show the nodal line semimetal state, including the all-carbon Mackay–Terrones crystal (MTC), anti-perovskite Cu₃PdN, pressed black phosphorus, and the CaP₃ family of materials, and we present the design principles for obtaining such novel states of matter.     

On the possibility of developing thermoelectric sensors based on multielement higher manganese silicide film structures

The possibility of designing thermoelectric sensors based on multielement structures of higher manganese silicide (HMS) polycrystalline films is considered. Test structures with various configurations are developed for studying electrical and thermoelectric parameters of polycrystalline HMS films. The geometrical sizes of the elements of test structures are chosen to match the grain size in polycrystalline HMS films. The test structures are prepared using the planar silicon technology. In these structures, the current-voltage characteristics, Hall constant, charge carrier concentration, and mobility are measured. The thermopower (α) and electrical conductivity (σ) are studied in a temperature range of T = 77–600 K, where α > 250 μV/K and electrical conductivity σ ∼ 20 (Ω cm)⁻¹. It is shown that the sensitivity and thermopowers increase upon a decrease in the cross-sectional area of the elements.     

On the nature of the dhcp to fcc transition under pressure in Pr and Pr-Th alloys

The results of electrical resistance (R), thermoelectric power (TEP) and X-ray diffraction measurements on praseodymium (Pr) and its alloys with thorium under pressure are reported. The maximum inR vsP curve exhibited by Pr persists only in the dhcp phase of PrTh alloy. X-ray measurements confirmed that in the alloys also the maximum inR vsP curve is due to the dhcp → fcc transition. Thus the behaviour of Pr and Pr-Th alloys is different from that of La and its alloys with Ce and Th where the maximum in theR vsP curve is electronic in origin and is exhibited by the dhcp, fcc and dist fcc phases.     

Material parameters for thermoelectric performance

The thermoelectric performance of a thermoelement is ideally defined in terms of the so-called figure-of-meritZ = α²σ/λ, where α,σ and λ refer respectively to the Seebeck coefficient, electrical conductivity and thermal conductivity of the thermoelement material. However, there are other parameters which are fairly good indicators of a material’s thermoelectric ‘worth’. A simple yet useful performance indicator is possible with only two parameters — energy gap and lattice thermal conductivity. This indicator can outline all potentially useful thermoelectric materials. Thermal conductivity in place of lattice thermal conductivity can provide some additional information about the temperature range of operation. Yet another performance indicator may be based on the slope of α vs. ln σ plots. α plotted against ln σ shows a linear relationship in a simplified model, but shows a variation with temperature and carrier concentration. Assuming that such a relationship is true for a narrow range of temperature and carrier concentration, one can calculate the slope m of α vs. ln σ plots against temperature and carrier concentrations. A comparison between the variation ofZT and slopem suggests that such plots may be useful to identify potential thermoelectric materials.     

Facile synthesis of nanostructured n-type SiGe alloys with enhanced thermoelectric performance using rapid solidification employing melt spinning followed by spark plasma sintering

SiGe alloy is widely used thermoelectric materials for high temperature thermoelectric generator applications. However, its high thermoelectric performance has been thus far realized only in alloys synthesized employing mechanical alloying techniques, which are time-consuming and employ several materials processing steps. In the current study, for the first time, we report an enhanced thermoelectric figure-of-merit (ZT) ∼ 1.1 at 900 °C in n-type Si₈₀Ge₂₀ nano-alloys, synthesized using a facile and up-scalable methodology consisting of rapid solidification at high optimized cooling rate ∼ 3.4 × 10⁷ K/s, employing melt spinning followed by spark plasma sintering of the resulting nano-crystalline melt-spun ribbons. This enhancement in ZT > 20% over its bulk counterpart, owes its origin to the nano-crystalline microstructure formed at high cooling rates, which results in crystallite size ∼7 nm leading to high density of grain boundaries, which scatter heat-carrying phonons. This abundant scattering resulted in a very low thermal conductivity ∼2.1 Wm⁻¹K⁻¹, which corresponds to ∼50% reduction over its bulk counterpart and is amongst the lowest reported thus far in n-type SiGe alloys. The synthesized samples were characterized using X-ray diffraction, scanning electron microscopy and transmission electron microscopy, based on which the enhancement in their thermoelectric performance has been discussed.