Experimental determination of the Lorenz number in Cu<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mrow /><mml:mrow><mml:mn>0.01</mml:mn></mml:mrow></mml:msub></mml:math>Bi<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mrow /><mml:mn>2</mml:mn></mml:msub></mml:math>Te<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mrow /><mml:mrow><mml:mn>2.7</mml:mn></mml:mrow></mml:msub></mml:math

Lukas, Kevin; Liu, Weishu; Joshi, Giri; Zebarjadi, Mona; Dresselhaus, M. S.; Ren, Zhifeng; Chen, Gang; Opeil, Cyril

doi:10.1103/physrevb.85.205410

Cited by 42 publications

(20 citation statements)

References 23 publications

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“…Additionally, a quantitative discussion on carrier density and mobility is more reasonable by using a two-band model. 36,37 Thermal conductivity k xx of polycrystalline NbP is shown in Fig. 4a, k xx increases rapidly with increasing temperature and reaches a peak value of B65 W m À1 K À1 near 85 K then decreases slowly to B39 W m À1 K À1 at room temperature.…”

Section: Resultsmentioning

confidence: 99%

Large Nernst power factor over a broad temperature range in polycrystalline Weyl semimetal NbP

Guin

Watzman

et al. 2018

Energy Environ. Sci.

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The discovery of topological materials has provided new opportunities to exploit advanced materials for heat-to-electricity energy conversion as they share many common characteristics with thermoelectric materials.In this work, we report the magneto-thermoelectric properties and Nernst effect of the topological Weyl semimetal NbP. We find that polycrystalline, bulk NbP shows a significantly larger Nernst thermopower than its conventional thermopower under magnetic field. As a result, a maximum Nernst power factor of B35 Â 10 À4 W m À1 K À2 is achieved at 9 T and 136 K, which is 4 times higher than its conventional power factor and is also comparable to that of state-of-the-art thermoelectrics. Moreover, the Nernst power factor maintains relatively large value over a broad temperature range. These results highlight that the enhancement of thermoelectric performance can be achieved in topological semimetals based on the Nernst effect and transverse transport.

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Section: Resultsmentioning

confidence: 99%

Large Nernst power factor over a broad temperature range in polycrystalline Weyl semimetal NbP

Guin

Watzman

et al. 2018

Energy Environ. Sci.

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“…Thus, the phonon energy in this temperature range is sufficient to change a 'hot' electron to 'cold,' and vice versa, as shown in Fig. 77 For this reason, when Lukas et al 78 experimentally determined the Lorenz number of Bi 0.88 Sb 0.12 , they measured up to temperatures around 140 K, whereas the onset of the bipolar thermal conductivity effect occurred at temperatures higher than 150 K. Below 140 K, they found that those are matched with eqn (8). An electron can be categorized as hot or cold depending on whether the energy of the electron is higher or lower than the Fermi energy.…”

Section: Comments On the Wiedemann-franz Lawmentioning

confidence: 94%

Strategies for engineering phonon transport in thermoelectrics

2015

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In this review, we discuss some of the representative strategies of phonon engineering by categorizing them into the methods affecting each component of phonon thermal conductivity, i.e., specific heat, phonon group velocity, and mean free path. In terms of specific heat, a large unit cell is beneficial in that it can minimize the fraction of thermal energy that can be transported since most of the energy is stored in the optical branches. In an artificial structure such as the superlattice, phonon bandgaps can be created through constructive interference by Bragg reflection, which reduces phonon group velocity.We further categorize the mean free path, i.e., scattering processes, into grain boundary scattering, impurity scattering, and phonon-phonon scattering. Rough-surfaced grains, nano-sized grains, and coated grains are discussed for enhancement of the grain boundary scattering. Alloy atoms, vacancies, nanoparticles, and nano-sized holes are treated as impurities, which limit the phonon mean free path. Lone pair electrons and acoustical-to-optical scattering are suggested for manipulating phonon-phonon scattering. We also briefly mention the limitation and temperature range in which the Wiedemann-Franz law is valid in order to achieve a better estimation of electronic thermal conductivity. This paper provides an organized view of phonon engineering so that this concept can be implemented synergistically with power factor enhancement approaches for design of thermoelectric materials. Fig. 1 Strategies of phonon engineering categorized into methods affecting each component of phonon thermal conductivity, i.e., specific heat, phonon group velocity, and scattering processes. Some of the figures are from the literature. 71,80 Fig. 3 Thermal conductivity of the (SrTiO 3 ) m /(CaTiO 3 ) n superlattice versus period thickness. 23 A TEM figure shows the interface quality of the superlattice. Also, a phonon dispersion curve showing phonon bandgaps is presented.

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“…37 In our case, the scattering parameter was determined as 1 according to the dependence of the Hall mobility m H on temperature T revealed in Fig. 5b.…”

Section: Thermal Transport Propertiesmentioning

confidence: 99%

Thermoelectric high-entropy alloys with low lattice thermal conductivity

et al. 2016

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Reducing lattice thermal conductivity is one of the most effective routes for improving the performance of thermoelectric materials. Herein, a novel alloy design concept, i.e., the high-entropy alloy concept, is introduced as a new strategy to reduce lattice thermal conductivity and the BiSbTe 1.5 Se 1.5 high-entropy alloy was chosen as a paradigm to demonstrate the applicability of this new approach. It was found that the lattice thermal conductivity of this high-entropy alloy is quite low, i.e., $0.47 W m À1 K À1 at 400 K, which results from its severe lattice-distortion. In addition, the minor addition of Ag could improve the absolute value of its Seebeck coefficient and further reduce its lattice thermal conductivity.Consequently, a peak ZT value of 0.63 was observed at 450 K for this alloy with the addition of 0.9 at% Ag. Our current results suggest that the revolutionary alloy design concept is a promising strategy for developing novel thermoelectric materials with desirable properties.

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Experimental determination of the Lorenz number in Cu0.01Bi2Te2.7

Cited by 42 publications

References 23 publications

Large Nernst power factor over a broad temperature range in polycrystalline Weyl semimetal NbP

Large Nernst power factor over a broad temperature range in polycrystalline Weyl semimetal NbP

Strategies for engineering phonon transport in thermoelectrics

Thermoelectric high-entropy alloys with low lattice thermal conductivity

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