We investigate the effect of non-analytical corrections on the phonon thermal transport properties in two-dimensional indium chalcogenide compounds. The longitudinal optical (LO) and transverse ...optical (TO) branches in the phonon dispersion are split near the Γ-point. The lattice thermal conductivity of monolayer InS is increased by 30.2% under non-analytical corrections because of the large LO-TO splitting at Γ-point. The predicted lattice thermal conductivities with non-analytical corrections at room temperature are 57.1 W/mK, 44.4 W/mK and 33.1 W/mK for the monolayer InS, InSe and InTe, respectively. The lattice thermal conductivity can be effectively reduced by nanostructures because the representative mean free paths are found very large in these monolayers. By quantifying the relative contribution of the phonon modes to the lattice thermal conductivity, we predict that the longitudinal acoustic branch is the main contributor to the lattice thermal conductivity. Due to the low lattice thermalconductivities of these monolayers, they can be useful in the nanoscale thermoelectric devices.
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Abstract Widespread application of thermoelectric devices for waste heat recovery requires low-cost high-performance materials. The currently available n-type thermoelectric materials are limited ...either by their low efficiencies or by being based on expensive, scarce or toxic elements. Here we report a low-cost n-type material, Te-doped Mg 3 Sb 1.5 Bi 0.5 , that exhibits a very high figure of merit zT ranging from 0.56 to 1.65 at 300−725 K. Using combined theoretical prediction and experimental validation, we show that the high thermoelectric performance originates from the significantly enhanced power factor because of the multi-valley band behaviour dominated by a unique near-edge conduction band with a sixfold valley degeneracy. This makes Te-doped Mg 3 Sb 1.5 Bi 0.5 a promising candidate for the low- and intermediate-temperature thermoelectric applications.
Recently SnSe, a layered chalcogenide material, has attracted a great deal of attention for its excellent p-type thermoelectric property showing a remarkable ZT value of 2.6 at 923 K. For ...thermoelectric device applications, it is necessary to have n-type materials with comparable ZT value. Here, we report that n-type SnSe single crystals were successfully synthesized by substituting Bi at Sn sites. In addition, it was found that the carrier concentration increases with Bi content, which has a great influence on the thermoelectric properties of n-type SnSe single crystals. Indeed, we achieved the maximum ZT value of 2.2 along b axis at 733 K in the most highly doped n-type SnSe with a carrier density of -2.1 × 10
cm
at 773 K.
In this paper, the transport properties of a two-dimensional Lieb lattice that is a line-centered square lattice are investigated in the presence of magnetic field and spin-orbit coupling. Specially, ...we address the temperature dependence of electrical and thermal conductivities as well as Seebeck coefficient due to spin-orbit interaction. We have exploited Green's function approach in order to study thermoelectric and transport properties of Lieb lattice in the context of Kane-Mele model Hamiltonian. The results for Seebeck coefficient show the sign of thermopower is positive in the presence of spin-orbit coupling. Also the temperature dependence of transport properties indicates that the increase of spin-orbit coupling leads to decrease thermal conductivity however the decrease of gap parameter causes the reduction of thermal conductivity. There is a peak in temperature dependence of thermal conductivity for all values of magnetic fields and spin-orbit coupling strengths. Both electrical and thermal conductivities increase with increasing the temperature at low amounts of temperature due to the increasing of transition rate of charge carriers and excitation of them to the conduction bands. Also we have studied the temperature dependence of Seebeck coefficient of Lieb monolayer due to both spin orbit coupling and magnetic field factors in details.
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We present the ultralow-temperature specific heat and thermal conductivity measurements on single crystals of triangular-lattice compound EtMe3SbPd(dmit)22, which has long been considered as a ...gapless quantum spin liquid candidate. In specific heat measurements, a finite linear term is observed, consistent with the previous work S. Yamashita et al., Nat. Commun. 2, 275 (2011). However, we do not observe a finite residual linear term in the thermal conductivity measurements, and the thermal conductivity does not change in a magnetic field of 6 T. These results are in sharp contrast to previous thermal conductivity measurements on EtMe3SbPd(dmit)22 M. Yamashita et al., Science 328, 1246 (2010), in which a huge residual linear term was observed and attributed to highly mobile gapless excitations, likely the spinons of a quantum spin liquid. In this context, the true ground state of EtMe3SbPd(dmit)22 has to be reconsidered.
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The Leidenfrost effect, namely the levitation of drops on hot solids
, is known to deteriorate heat transfer at high temperature
. The Leidenfrost point can be elevated by texturing materials to ...favour the solid-liquid contact
and by arranging channels at the surface to decouple the wetting phenomena from the vapour dynamics
. However, maximizing both the Leidenfrost point and thermal cooling across a wide range of temperatures can be mutually exclusive
. Here we report a rational design of structured thermal armours that inhibit the Leidenfrost effect up to 1,150 °C, that is, 600 °C more than previously attained, yet preserving heat transfer. Our design consists of steel pillars serving as thermal bridges, an embedded insulating membrane that wicks and spreads the liquid and U-shaped channels for vapour evacuation. The coexistence of materials with contrasting thermal and geometrical properties cooperatively transforms normally uniform temperatures into non-uniform ones, generates lateral wicking at all temperatures and enhances thermal cooling. Structured thermal armours are limited only by their melting point, rather than by a failure in the design. The material can be made flexible, and thus attached to substrates otherwise challenging to structure. Our strategy holds the potential to enable the implementation of efficient water cooling at ultra-high solid temperatures, which is, to date, an uncharted property.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
In almost all fusion and accelerator experiments presently in operation or under construction, current leads (CLs), which feed the magnets, use high-temperature superconducting (HTS) materials to ...reduce the total cooling power consumption of the He refrigerator. These CLs carry currents in the range of 10-68 kA. The Karlsruhe Institute of Technology successfully designed, built, and tested the 70-kA demonstrator CL for the ITER magnets, which was subsequently followed by the 18.2-kA HTS CLs for the Wendelstein 7-X stellarator and the 20-kA and 26-kA HTS CLs for the JT-60SA tokamak. All these CLs use the first-generation HTS material BSCCO. The HTS part of the CL is now the focus of a new development aiming at a substitution of BSCCO by the next-generation HTS material RE BCO. To limit the heat load to the cryostat, the stabilizer material of the RE BCO coated tapes requires a low thermal conductivity. In addition, stabilizers with a sufficiently high electrical conductivity are mandatory in order to protect the CL in case of a quench of the RE BCO tapes. A part of this new development is therefore a detailed material property investigation of RE BCO coated conductor single tapes with a low thermal conductivity, in order to define a suitable conductor for a 20-kA CL and to create a database for the subsequent technical optimization process. This paper summarizes the measurement results of the thermal conductivity, electric resistivity, and specific heat capacity for RE BCO single tapes with a low heat leakage. The results are analyzed with regard to earlier investigations of the BSCCO tapes used in the Wendelstein CLs serving as a reference for a future RE BCO CL.
High-temperature superconducting (HTS) bulk materials of RE-B-Cu-O (RE: Y or rare-earth elements) exhibit excellent Formula Omitted properties, even at 77 K, leading to current leads with large ...current capacity and superior magnetic field tolerance. The thermal conductivity of HTS bulk materials is two orders of magnitude smaller than that of the conventional current lead material of copper, and Dy-B-Cu-O has particularly low thermal conductivity in the RE-B-Cu-O family. Unlike HTS wires, HTS bulks have no metal sheath such as silver or silver alloys with high thermal conductivity, resulting in the reduction of heat leak through the current lead, even in the compact size. Although they are a kind of brittle ceramic or oxide, HTS bulks can be transformed into robust current leads by reinforcing them with the support cover made of glass-fiber-reinforced plastics with low thermal conductivity and high strength. In addition to excellent mechanical stress tolerance, HTS bulk current leads also have a robust structure that minimizes thermal stress, which was experimentally demonstrated by a rapid cooling test to liquid nitrogen over 100 cycles. Due to distinctive advantages such as compactness, robustness, and superior field tolerance, more than 500 pieces of HTS bulk current leads have been successfully provided so far.
Materials with high thermal conductivity (κ) are of technological importance and fundamental interest. We grew cubic boron nitride (cBN) crystals with controlled abundance of boron isotopes and ...measured κ greater than 1600 watts per meter-kelvin at room temperature in samples with enriched
B or
B. In comparison, we found that the isotope enhancement of κ is considerably lower for boron phosphide and boron arsenide as the identical isotopic mass disorder becomes increasingly invisible to phonons. The ultrahigh κ in conjunction with its wide bandgap (6.2 electron volts) makes cBN a promising material for microelectronics thermal management, high-power electronics, and optoelectronics applications.
Using first principles calculations, we predict the thermal conductivity of the two-dimensional materials black phosphorene and blue phosphorene. Black phosphorene has an unprecedented thermal ...conductivity anisotropy ratio of three, with predicted values of 110 W/m-K and 36 W/m-K along its armchair and zigzag directions at a temperature of 300 K. For blue phosphorene, which is isotropic with a zigzag structure, the predicted value is 78 W/m-K. The two allotropes show strikingly different thermal conductivity accumulation, with phonons of mean free paths between 10 nm and 1 μm dominating in black phosphorene, while a much narrower band of mean free paths (50-200 nm) dominate in blue phosphorene. Black phosphorene shows intriguing potential for strain-tuning of its thermal conductivity tensor.
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