Search for new thermoelectric materials with low Lorenz number

McKinney, Robert; Gorai, Prashun; Stevanović, Vladan; Toberer, Eric S.

doi:10.1039/c7ta04332e

Cited by 67 publications

(58 citation statements)

References 36 publications

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“…In semiconductors, the μ H character is mainly governed by the interaction between majority carriers and their scattering source at the specific temperature. Consistently, temperature dependences of μ H for all investigated samples indicate that the electronic transports are mainly governed by acoustic phonon scattering (δ < −1.5), which has an energy-dependent scattering rate proportional to the density of states, [11] since other scattering mechanisms have different scattering exponents (δ ≥ −0.5) and their contributions to μ H become miniscule with increasing temperature over 300 K. [21][22][23] The n C is determined from the measured Hall coefficient R H (n C = 1/qR H , where q is an elementary charge). However, the slope of μ H (Figure 2a,c) as a function of temperature does not change meaningfully in Te-MS compared to MS.…”

Section: Doi: 101002/aenm201800065supporting

confidence: 67%

“…[11] The fundamental but most important challenge for the high TE performance still lies in breaking trade-offs or finding hidden parameter enabling individual control of electronic and/or thermal transport properties. [11] The fundamental but most important challenge for the high TE performance still lies in breaking trade-offs or finding hidden parameter enabling individual control of electronic and/or thermal transport properties.…”

Section: Doi: 101002/aenm201800065mentioning

confidence: 99%

“…independent of σ. [11] The fundamental but most important challenge for the high TE performance still lies in breaking trade-offs or finding hidden parameter enabling individual control of electronic and/or thermal transport properties.…”

Section: Doi: 101002/aenm201800065mentioning

confidence: 99%

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Effect of Dislocation Arrays at Grain Boundaries on Electronic Transport Properties of Bismuth Antimony Telluride: Unified Strategy for High Thermoelectric Performance

Hwang

Kim

et al. 2018

Advanced Energy Materials

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Harnessing individual electronic and thermal transport properties selectively has long been a fundamental goal of achieving high thermoelectric (TE) performance in many materials. TE energy conversion efficiency of materials is directly proportional to the material-dependent parameter as known as a dimensionless figure of merit, zT. In principle, twofold intercorrelated relations of physical parameters i) between electrical conductivity (σ) and Seebeck coefficient (S) and ii) between σ and total thermal conductivity (κ total ) in TE semiconductors are strongly correlated each other and the trade-offs have been major obstacles for improving zT, which is determined by zT = S 2 σ T/κ total where T is temperature and κ total consists of the sum of electronic (κ elec ) and lattice (κ latt ) contributions to thermal conductivity.Many efforts have been demonstrated to overcome these long historic cliché issues on thermoelectrics. Concerning about electronic transports, several distinct strategies have been proposed for exclusively enhancing power factor (PF: S 2 σ) by utilizing resonance state in Tl-doped p-type PbTe, [1,2] the convergence of electronic bands, [3] and the doping modulation in nanocomposites. [4] However, these approaches are not widely applicable to all TE materials since the enhancement of PF through such strategies utterly depends on the unique electronic band structure of the individual material. Apart from the optimization of PF, remarkable enhancements of the zT have been achieved mostly due to the reduction of the κ latt via increased phonon scattering utilizing structural defects in nanostructured materials, such as grain boundaries, interfaces, dislocations, and precipitates. [4][5][6][7] Further, efforts to find a new material with intrinsically low thermal conductivity have been devoted. [8][9][10] In fact, little room remains for further reducing κ latt in nanostructured single-phase materials because κ latt cannot be reduced below the amorphous limit, which has been already achieved in the state-of-the-art nanostructured TE materials. Moreover, it has been widely recognized that κ elec cannot be decoupled from σ. However, there is a possibility to reduce the κ elec value by decreasing Lorenz number (L) since L is a band structure-dependent parameter of material but relatively Taming electronic and thermal transport properties is the ultimate goal in the quest to achieve unprecedentedly high performance in thermoelectric (TE) materials. Most state-of-the-art TE materials are inherently narrow bandgap semiconductors, which have an inevitable contribution from minority carriers, concurrently decreasing Seebeck coefficient and increasing thermal conductivity. Nevertheless, the restraint control of minority carrier transport is seldom considered as a key element to enhance the TE figure of merit (zT). Herein, it is verified that the localized dislocation arrays at grain boundaries enable the suppression of minority carrier contribution to electronic transport properties, resulting in an increase ...

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Section: Doi: 101002/aenm201800065supporting

confidence: 67%

Section: Doi: 101002/aenm201800065mentioning

confidence: 99%

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Effect of Dislocation Arrays at Grain Boundaries on Electronic Transport Properties of Bismuth Antimony Telluride: Unified Strategy for High Thermoelectric Performance

Hwang

Kim

et al. 2018

Advanced Energy Materials

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“…SF, for which we give the explicit formula later in the text, is closest to unity when the DOS has abrupt changes and lower when the DOS is smooth and gradual, which follows the conventional wisdom that abrupt changes near the Fermi level lead to better TE properties. A high throughput search among the known compounds confirmed that the SF should approach unity to maximize ZT [40]. The required shape for the DOS to achieve it resembles a step function, which is also the shape of the DOS in 2D materials with a parabolic bandstructure.…”

mentioning

confidence: 89%

“…In an effort to formulate a metric that can help to identify materials with single cut-off energy, as originally proposed by Mahan [39], the shape factor (SF) was proposed as a measure of the asymmetry in the density of states (DOS) [40]. SF, for which we give the explicit formula later in the text, is closest to unity when the DOS has abrupt changes and lower when the DOS is smooth and gradual, which follows the conventional wisdom that abrupt changes near the Fermi level lead to better TE properties.…”

mentioning

confidence: 99%

Materials selection rules for optimum power factor in two-dimensional thermoelectrics

Kommini

Akšamija

2019

J. Phys. Mater.

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Two-dimensional (2D) materials have emerged as the ideal candidates for many applications, including nanoelectronics, low-power devices, and sensors. Several 2D materials have been shown to possess large Seebeck coefficients, thus making them suitable for thermoelectric (TE) energy conversion. Whether even higher TE power factors can be discovered among the ≈2000 possible 2D materials (Mounet et al 2018 Nat. Nanotechnol. 13 246-52) is an open question. This study aims at formulating selection rules to guide the search for superior 2D TE materials without the need for expensive atomistic simulations. We show that a 2D material having a combination of low effective mass, higher separation in the height of the step-like density of states, and valley splitting, which is the energy difference between the bottom of conduction band and the satellite valley, equal to 5 k B T will lead to a higher TE power factor. Further, we find that inelastic scattering with optical phonons plays a significant role: if inelastic scattering is the dominant mechanism and the energy of the optical phonon equals 5 k B T, then the TE power factor is maximized. Starting from a model for carrier transport in MoS 2 and progressively introducing the aforementioned features results in a two-orders-ofmagnitude improvement in the power factor. Compared to the existing selection rules or material descriptors, features identified in this study provide the ability to comprehensively evaluate TE capability of a material and helps in identifying future TE materials suitable for applications in wasteheat scavenging, thermal sensors, and nanoelectronics cooling.

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High Power Factors of Thermoelectric Colusites Cu₂₆T₂Ge₆S₃₂ (T = Cr, Mo, W): Toward Functionalization of the Conductive “Cu–S” Network

Kumar

Supka

Lemoine

et al. 2018

Advanced Energy Materials

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The introduction of hexavalent T6+ cations in p‐type thermoelectric colusites Cu26T2Ge6S32 (T = Cr, Mo, W) leads to the highest power factors among iono‐covalent sulfides, ranging from 1.17 mW m−1 K−2 at 700 K for W to a value of 1.94 mW m−1 K−2 for Cr. In Cu26Cr2Ge6S32, ZT reaches values close to unity at 700 K. The improvement of the transport properties in these new sulfides is explained on the basis of electronic structure and transport calculations keeping in mind that the relaxation time is significantly influenced by the size and the electronegativity of the interstitial T cation. The rationale is based on the concept of a conductive “Cu–S” network, which in colusites corresponds to the more symmetric parent structure sphalerite. A detailed structural analysis of these colusites shows that the distortion of the conductive network is influenced by the presence in the structure of mixed octahedral–tetrahedral [TS4]Cu6 complexes where the T cations are underbonded to sulfur and form metal–metal interactions with copper, Cu–T distances decreasing from 2.76 Å for W to 2.71 Å for Cr. The interactions between these complexes are responsible for the outstanding electronic transport properties. By contrast, the thermal conductivity is not significantly affected.

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Search for new thermoelectric materials with low Lorenz number

Abstract: High-throughput search for thermoelectric materials with low Lorenz number based on DOS shape and thermoelectric quality factor.

Cited by 67 publications

References 36 publications

Effect of Dislocation Arrays at Grain Boundaries on Electronic Transport Properties of Bismuth Antimony Telluride: Unified Strategy for High Thermoelectric Performance

Effect of Dislocation Arrays at Grain Boundaries on Electronic Transport Properties of Bismuth Antimony Telluride: Unified Strategy for High Thermoelectric Performance

Materials selection rules for optimum power factor in two-dimensional thermoelectrics

High Power Factors of Thermoelectric Colusites Cu₂₆T₂Ge₆S₃₂ (T = Cr, Mo, W): Toward Functionalization of the Conductive “Cu–S” Network

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Search for new thermoelectric materials with low Lorenz number

Abstract: High-throughput search for thermoelectric materials with low Lorenz number based on DOS shape and thermoelectric quality factor.

Cited by 67 publications

References 36 publications

Effect of Dislocation Arrays at Grain Boundaries on Electronic Transport Properties of Bismuth Antimony Telluride: Unified Strategy for High Thermoelectric Performance

Effect of Dislocation Arrays at Grain Boundaries on Electronic Transport Properties of Bismuth Antimony Telluride: Unified Strategy for High Thermoelectric Performance

Materials selection rules for optimum power factor in two-dimensional thermoelectrics

High Power Factors of Thermoelectric Colusites Cu26T2Ge6S32 (T = Cr, Mo, W): Toward Functionalization of the Conductive “Cu–S” Network

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Product

Resources

About

High Power Factors of Thermoelectric Colusites Cu₂₆T₂Ge₆S₃₂ (T = Cr, Mo, W): Toward Functionalization of the Conductive “Cu–S” Network