When thermoelectrics reached the nanoscale

Heremans, Joseph P.; Dresselhaus, M. S.; Bell, Lon E.; Morelli, Donald T.

doi:10.1038/nnano.2013.129

Cited by 569 publications

(376 citation statements)

References 27 publications

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“…64,65 However, our facile, low-temperature solution-phase synthesis could be useful as a means of mitigating this problem, as it allows for reduction in grain size or nanostructuring. 13,[66][67][68][69] Characterization of LiZnSb using solid state NMR. Surface passivating ligands are a critical feature of phases prepared by low-temperature solution-phase synthesis.…”

Section: Resultsmentioning

confidence: 99%

Expanding the I–II–V Phase Space: Soft Synthesis of Polytypic Ternary and Binary Zinc Antimonides

et al. 2018

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Soft chemistry methods offer the possibility of synthesizing metastable and kinetic products that are unobtainable through thermodynamically-controlled, high-temperature reactions. A recent solution-phase exploration of Li-Zn-Sb phase space revealed a previously unknown cubic half-Heusler MgAgAs-type LiZnSb polytype. Interestingly, this new cubic phase was calculated to be the most thermodynamically stable, despite prior literature reporting only two other ternary phases (the hexagonal half-Heusler LiGaGe-type LiZnSb, and the full-Heusler Li2ZnSb). This surprising discovery, coupled with the intriguing optoelectronic and transport properties of many antimony containing Zintl phases, required a thorough exploration of syn-thetic parameters. Here, we systematically study the effects that different precursor concentrations, injection order, nucleation and growth temperatures, and reaction time have on the solution-phase synthesis of these materials. By doing so, we identify conditions that selectively yield several unique ternary (c-LiZnSb vs. h*-LiZnSb), binary (ZnSb vs. Zn8Sb7), and metallic (Zn, Sb) products. Further, we find one of the ternary phases adopts a variant of the previously observed hexagonal LiZnSb struc-ture. Our results demonstrate the utility of low temperature solution phase-soft synthesis-methods in accessing and mining a rich phase space. We anticipate that this work will motivate further exploration of multinary I-II-V compounds, as well as encourage similarly thorough investigations of related Zintl systems by solution phase methods. Disciplines Materials ChemistryComments "This document is the unedited Author's version of a Submitted Work that was subsequently accepted for publication in Chemistry of Materials, copyright © American Chemical Society after peer review. To access the final edited and published work see http://dx.doi.org/10.1021/acs.chemmater.8b02910. ABSTRACT: Soft chemistry methods offer the possibility of synthesizing metastable and kinetic products that are unobtainable through thermodynamically-controlled, high-temperature reactions. A recent solution-phase exploration of Li-Zn-Sb phase space revealed a previously unknown cubic half-Heusler MgAgAs-type LiZnSb polytype. Interestingly, this new cubic phase was calculated to be the most thermodynamically stable, despite prior literature reporting only two other ternary phases (the hexagonal half-Heusler LiGaGe-type LiZnSb, and the full-Heusler Li2ZnSb). This surprising discovery, coupled with the intriguing optoelectronic and transport properties of many antimony containing Zintl phases, required a thorough exploration of synthetic parameters. Here, we systematically study the effects that different precursor concentrations, injection order, nucleation and growth temperatures, and reaction time have on the solution-phase synthesis of these materials. By doing so, we identify conditions that selectively yield several unique ternary (c-LiZnSb vs. h*-LiZnSb), binary (ZnSb vs. Zn8Sb7), and metallic (Zn, Sb) products. Furt...

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Section: Resultsmentioning

confidence: 99%

Expanding the I–II–V Phase Space: Soft Synthesis of Polytypic Ternary and Binary Zinc Antimonides

et al. 2018

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“…Moreover, lower dimensional structures with numerous interfaces, very effectively scatter the heat-carrying phonons and thus significantly reduce the lattice thermal conductivity. 3,7,8 The other important idea was the 'Phonon Glass Electron Crystal' (PGEC) paradigm, proposed by Slack. 9 It describes an ideal architecture of new TE materials with potentially independent electrical and thermal transport networks.…”

Section: Introductionmentioning

confidence: 99%

On the tuning of electrical and thermal transport in thermoelectrics: an integrated theory–experiment perspective

et al. 2016

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During the last two decades, we have witnessed great progress in research on thermoelectrics. There are two primary focuses. One is the fundamental understanding of electrical and thermal transport, enabled by the interplay of theory and experiment; the other is the substantial enhancement of the performance of various thermoelectric materials, through synergistic optimisation of those intercorrelated transport parameters. Here we review some of the successful strategies for tuning electrical and thermal transport. For electrical transport, we start from the classical but still very active strategy of tuning band degeneracy (or band convergence), then discuss the engineering of carrier scattering, and finally address the concept of conduction channels and conductive networks that emerge in complex thermoelectric materials. For thermal transport, we summarise the approaches for studying thermal transport based on phonon-phonon interactions valid for conventional solids, as well as some quantitative efforts for nanostructures. We also discuss the thermal transport in complex materials with chemical-bond hierarchy, in which a portion of the atoms (or subunits) are weakly bonded to the rest of the structure, leading to an intrinsic manifestation of part-crystalline part-liquid state at elevated temperatures. In this review, we provide a summary of achievements made in recent studies of thermoelectric transport properties, and demonstrate how they have led to improvements in thermoelectric performance by the integration of modern theory and experiment, and point out some challenges and possible directions. INTRODUCTION Thermoelectric (TE) materials are materials that can generate useful electric potentials when subjected to a temperature gradient (known as the Seebeck effect). Conversely, they also transfer heat against the temperature gradient when a current is driven against this potential (known as the Peltier effect). They are promising energy materials with many applications, such as waste heat harvesting, radioisotope TE power generation, and solid state Peltier refrigeration, all of which are driving growing research interest. A key challenge is to improve the TE properties in order to obtain more efficient energy conversion and in turn enable new practical applications. Good TE materials must have excellent electrical transport properties, measured by the TE power factor ( = S 2 σ, where S is the Seebeck coefficient and σ is the electrical conductivity), and also a very low thermal conductivity κ (composed of the electronic contribution κ e , the lattice contribution κ L , and the bipolar contribution κ bi ). Combining the two aspects gives us the dimensionless figure of merit ZT,

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“…Such local heating affects crucially the device properties [13][14][15][16], and have significant influence on some physical processes, such as thermoelectric conversion [17][18][19], heat dissipation [8,19], and electron-phonon interactions [20,21]. All these studies, however, leave open the question of what precisely is a "local temperature" in a nonequilibrium system, a concept that has a well-established meaning only in global equilibrium.…”

mentioning

confidence: 99%

Thermodynamic meaning of local temperature of nonequilibrium open quantum systems

Zheng

Yan

et al. 2016

Phys. Rev. B

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Measuring the local temperature of nanoscale systems out of equilibrium has emerged as a new tool to study local heating effects and other local thermal properties of systems driven by external fields. Although various experimental protocols and theoretical definitions have been proposed to determine the local temperature, the thermodynamic meaning of the measured or defined quantities remains unclear. By performing analytical and numerical analysis of bias-driven quantum dot systems both in the noninteracting and strongly-correlated regimes, we elucidate the underlying physical meaning of local temperature as determined by two definitions: the zero-current condition that is widely used but not measurable, and the minimal-perturbation condition that is experimentally realizable. We show that, unlike the zero-current one, the local temperature determined by the minimalperturbation protocol establishes a quantitative correspondence between the nonequilibrium system of interest and a reference equilibrium system, provided the probed system observable and the related electronic excitations are fully local. The quantitative correspondence thus allows the wellestablished thermodynamic concept to be extended to nonequilibrium situations.PACS numbers: 05.70. Ln, 71.27.+a, 73.23.Hk, 73.63.Kv Probing the variation of local temperatures in systems out of equilibrium has become a subject of intense experimental interest in physics [1][2][3][4][5], chemistry [6][7][8] and life sciences [9][10][11][12]. With the development of high-resolution thermometry techniques, measurement of some sort of temperature distributions of nonequilibrium systems has been realized, such as in graphene-metal contacts [4], gold interconnect structures [5], and living cells [12].Local electronic and phononic excitations occur in nanoelectronic devices subject to a bias voltage or thermal gradient, and hence the devices are supposedly at a local temperature somewhat higher than the background temperature. Such local heating affects crucially the device properties [13][14][15][16], and have significant influence on some physical processes, such as thermoelectric conversion [17][18][19], heat dissipation [8,19], and electron-phonon interactions [20,21]. All these studies, however, leave open the question of what precisely is a "local temperature" in a nonequilibrium system, a concept that has a well-established meaning only in global equilibrium.Over the past decade, numerous experimental [15,[22][23][24][25][26][27] and theoretical [28][29][30][31][32][33][34][35][36][37][38] efforts have been made to provide practical and meaningful definitions of local temperature for nonequilibrium systems that bear a close conceptual resemblance to the thermodynamic one. However, it has remained largely unclear how to physically interpret the defined local temperature, and how to associate the measured value with the magnitudes of local excitations and local heating at a quantitative level.This work aims at elucidating these fundamental issues through analyti...

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When thermoelectrics reached the nanoscale

Cited by 569 publications

References 27 publications

Expanding the I–II–V Phase Space: Soft Synthesis of Polytypic Ternary and Binary Zinc Antimonides

Expanding the I–II–V Phase Space: Soft Synthesis of Polytypic Ternary and Binary Zinc Antimonides

On the tuning of electrical and thermal transport in thermoelectrics: an integrated theory–experiment perspective

Thermodynamic meaning of local temperature of nonequilibrium open quantum systems

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