Thermoelectric quantum-dot superlattices with high ZT

Harman, T. C.; Taylor, Patrick J.; Spears, D. L.; Walsh, Michael P.

doi:10.1007/s11664-000-0117-1

Cited by 279 publications

(140 citation statements)

References 18 publications

(18 reference statements)

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“…The state-of-the-art materials for thermoelectric cooling applications are alloys, it is necessary for the competing technologies based on Bi 2 Te 3 /Sb 2 Te 3 and Bi 2 Te 3 /Bi 2 Se 3 with ZT ¼ 1 and ZT ¼ 4, respectively [13,14]. Nanostructuring these thermoelectric materials has recently emerged as a successful strategy to gain factorial enhancements in ZT, unsettled to quantum and classical size effects of the charge and heat carriers, respectively [8,9,15,16]. Quantum confinement of charge carriers is believed to be due to an enhancement in the Seebeck coefficient (S) and electrical conductivity (s) owing to an increased density of states at the Fermi level [16][17][18].…”

Section: Introductionmentioning

confidence: 99%

Low temperature reduction route to synthesise bismuth telluride (Bi₂Te₃) nanoparticles: structural and optical studies

Srivastava

2013

Journal of Experimental Nanoscience

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Herein, we report the synthesis of highly yielded bismuth-telluride (Bi 2 Te 3 ) nanoparticles at 50 C by direct wet chemical route in which the bismuth and tellurium precursors have been dissolved in deionised water, ethylene glycol and hydrazine hydrate. This method is very facile, inexpensive and less hazardous and ensures almost complete yield of the precursors. The powder product was well characterised by powder X-ray diffraction, UV-Vis spectroscopy, Fourier transform infrared spectroscopy, energy dispersive X-ray diffraction, transmission electron microscopy and scanning electron microscopy. It is investigated that the synthesised powder has a rhombohedral structure of Bi 2 Te 3 with average diameters of the particles about 35 nm. Thus, the synthesis process has been modified to design nanostructures of thermoelectric materials with related crystal structures.Keywords: nanostructures; chemical synthesis; electron microscopy; X-ray diffraction; optical properties IntroductionTransition-metal chalcogenides in nanocrystalline form exhibit numerous interesting and useful characteristic properties that differ from their bulk counterpart. As a consequence of the quantum confinement effect, nanomaterials have received attention due to their size-dependent optical, physical, mechanical, thermal and chemical properties. During the past few decades, with the rapid enlargement of human population, the consumption of traditional energy has increased exponentially. Therefore, more and more researchers come to pay close attention to new sources of energy. Thermoelectric (TE) device emerges as a new kind of hot substance that can directly achieve the conversion between heat and electricity, which can maximise the use of waste heat and electricity in daily life. TE materials can convert waste heat energy to useful electrical energy for power generation and imperative applications in thermoelectric micro-cooling devices. The properties of a TE material can be explained by the energy conversion efficiency which mainly depends on the material's dimensionless TE figure-of-merit (ZT) ¼ sS 2 T/k, where s is the electrical conductivity, S is the Seebeck coefficient, T is the operating temperature and k is the thermal conductivity. The quantity 'S 2 s' is commonly considered as 'power factor'. An increment in power factor and a decrease in thermal conductivity are essential requirements for the enhancing ZT value. For a fine TE material, it posses high 's' and a low 'k'. Spongy TE materials [1] such as skutterudites [2] and clathrate crystals [3]

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Section: Introductionmentioning

confidence: 99%

Low temperature reduction route to synthesise bismuth telluride (Bi₂Te₃) nanoparticles: structural and optical studies

Srivastava

2013

Journal of Experimental Nanoscience

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“…5) may be evidence that the formation of Te 0 and Bi x Te y was the preferred reaction in this region. The intermediate reduction wave extends from -0.02 mV to -0.12 mV involved the formation of Bi x Sb y Te 3 ternary alloys with stoichiometric (Bi 0.75 Sb 0.25 ) 2 Te 3 formed at -0.05 mV. The third reduction wave extends from -0.14 mV to -0.18 mV involved the formation of Sb-rich BiSbTe ternary alloys.…”

Section: Resultsmentioning

confidence: 99%

“…Various techniques have been used to synthesize nanostructured TE materials such as chemical vapour deposition (CVD) [2], molecular beam epitaxy (MBE) [3], vapor-liquid-solid (VLS) process [4], hydrothermal process [5] and electrodeposition [6]. Compared to other methods, electrodeposition is one of the most cost-effective techniques for the fabrication of nanostructured materials.…”

Section: Introductionmentioning

confidence: 99%

Electrochemically deposited BiTe-based nanowires for thermoelectric applications

Kok

Rahman

et al. 2014

AIP Conference Proceedings

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“…However experimental results with GaAs/AlGaAs QWIPs show that it is possible have lateral momentum non-conserved without affecting much the mobility of carriers moving above the barrier (see appendix). Controlled roughness of the superlattice interfaces during the growth or taking advantage of well designed quantum dot structures can create the required inhomogeneities [17]. The improvement in the effective power factor through thermionic emission can be combined with the other methods to reduce the phonon thermal conductivity in superlattices and thus obtain higher thermoelectric figure-ofmerit ZT [18][19][20].…”

Section: Resultsmentioning

confidence: 99%

Conservation of Lateral Momentum in Heterostructure Integrated Thermionic Coolers

Vashaee

Shakouri

2001

MRS Proc.

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Thin film thermionic coolers use selective emission of hot electrons over a heterostructure barrier layer from emitter to collector resulting in evaporative cooling. In this paper a detailed theory of electron transport perpendicular to the multilayer superlattice structures is presented. Using Fermi-Dirac statistics, density-of-states for a finite quantum well and the quantum mechanical reflection coefficient, the currentvoltage characteristics and the cooling power density are calculated. The resulting equations are valid in a wide range of temperatures and electric fields. It is shown that conservation of lateral momentum plays an important role in the device characteristics. If the lateral momentum of the hot electrons is conserved in the thermionic emission process, only carriers with sufficiently large kinetic energy perpendicular to the barrier can pass over it and cool the emitter junction. However, if there is no conservation of lateral momentum, the number of electrons participating in thermionic emission will dramatically increase. The theoretical calculations are compared with the experimental dark current characteristics of quantum well infrared photodetectors and good agreement over a wide temperature range is obtained. Calculations for InGaAs/InGaAsP superlattice structures show that the effective thermoelectric power factor (electrical conductivity times the square of the effective Seebeck coefficient) can be improved comparing to that of bulk material. We will also discuss methods by which the conservation of lateral momentum in thermionic emission process can be altered such as by creating a controlled roughness at the interface of the superlattice barriers. The improvement in the effective power factor through thermionic emission can be combined with the other methods to reduce the phonon thermal conductivity in superlattices and thus obtain higher thermoelectric figure-of-merit ZT.

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Thermoelectric quantum-dot superlattices with high ZT

Abstract: Letter L1

Cited by 279 publications

References 18 publications

Low temperature reduction route to synthesise bismuth telluride (Bi₂Te₃) nanoparticles: structural and optical studies

Low temperature reduction route to synthesise bismuth telluride (Bi₂Te₃) nanoparticles: structural and optical studies

Electrochemically deposited BiTe-based nanowires for thermoelectric applications

Conservation of Lateral Momentum in Heterostructure Integrated Thermionic Coolers

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Thermoelectric quantum-dot superlattices with high ZT

Abstract: Letter L1

Cited by 279 publications

References 18 publications

Low temperature reduction route to synthesise bismuth telluride (Bi2Te3) nanoparticles: structural and optical studies

Low temperature reduction route to synthesise bismuth telluride (Bi2Te3) nanoparticles: structural and optical studies

Electrochemically deposited BiTe-based nanowires for thermoelectric applications

Conservation of Lateral Momentum in Heterostructure Integrated Thermionic Coolers

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Product

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Low temperature reduction route to synthesise bismuth telluride (Bi₂Te₃) nanoparticles: structural and optical studies

Low temperature reduction route to synthesise bismuth telluride (Bi₂Te₃) nanoparticles: structural and optical studies