Effect of thermal disorder on high figure of merit in PbTe

Kim, Hyoungchul; Kaviany, Massoud

doi:10.1103/physrevb.86.045213

Cited by 46 publications

(64 citation statements)

References 47 publications

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“…13 Moreover, a thermal-disordered lead chalcogenide structure (Pb atoms are moved further offcentered compared to the chalcogenide atoms with increasing T) was proposed and adopted to fully explain the temperaturedependent band convergence of lead chalcogenides. 53 Theoretical calculation of this thermal-disordered structure based on ab initio molecular dynamics has been performed and finds that the convergence temperature for PbTe is about 450 K, 54 which is consistent with the former experimental results from electrical and optical measurement with photon energies less than the fundamental gap. 51 However, recent free carrier absorption measurements, 55 temperature-dependent angle-resolved photoemission spectroscopy study, 55,56 and theoretical calculation 57 (considering both lattice thermal expansion and electron-phonon interaction) reveal that the actual convergence temperature is above 700 K, much higher than the previous results.…”

Section: Valley Degeneracysupporting

confidence: 70%

Valleytronics in thermoelectric materials

et al. 2018

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The central theme of valleytronics lies in the manipulation of valley degree of freedom for certain materials to fulfill specific application needs. While thermoelectric (TE) materials rely on carriers as working medium to absorb heat and generate power, their performance is intrinsically constrained by the energy valleys to which the carriers reside. Therefore, valleytronics can be extended to the TE field to include strategies for enhancing TE performance by engineering band structures. This review focuses on the recent progress in TE materials from the perspective of valleytronics, which includes three valley parameters (valley degeneracy, valley distortion, and valley anisotropy) and their influencing factors. The underlying physical mechanisms are discussed and related strategies that enable effective tuning of valley structures for better TE performance are presented and highlighted. It is shown that valleytronics could be a powerful tool in searching for promising TE materials, understanding complex mechanisms of carrier transport, and optimizing TE performance.npj Quantum Materials (2018) 3:9 ; doi:10.1038/s41535-018-0083-6 INTRODUCTIONThe demand for renewable energy harvesting has been growing because of the limited fossil fuels and increasing worldwide energy consumption. Thermoelectric (TE) materials, which have the capability of converting heat directly into electricity under a temperature gradient, have been regarded as an alternative option to alleviate energy shortage.1 Though TE devices have already been applied in deep space exploration and solid state cooling, 2,3 the relatively low energy conversion efficiency limits their wide commercialization, 4 which is mainly constrained by the performance of TE materials as characterized by the dimensionless figure of merit, zT = α 2 σT/(κ e + κ L ), where α is the Seebeck coefficient, σ is the electrical conductivity, κ e and κ L are, respectively, the electronic and lattice contributions to the total thermal conductivity κ, and T is the absolute temperature.5 Since all three physical properties (α, σ, and κ) are carrier concentration dependent, zT could reach its maximum value at an optimized carrier concentration. zT max is determined by a combination of intrinsic physical parameters as well as the temperature, all of which integrated into a term called the TE quality factor, B. Higher quality factor B leads to higher zT max at a fixed temperature. With a single parabolic band model in the nondegenerate limit, B could be expressed as:

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Section: Valley Degeneracysupporting

confidence: 70%

Valleytronics in thermoelectric materials

et al. 2018

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“…3(d)]. Recent studies show that, despite its nominal ionic charge of 2.0, PbTe is only weakly ionic with an effective ionic charge of 0.72 [11,34]. This is consistent with the observation that the TA phonon of PbTe shows significantly diverging v g at low frequencies [ Fig.…”

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confidence: 77%

Intrinsic low thermal conductivity in weakly ionic rocksalt structures

et al. 2015

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“…22 The theoretical studies based on quasiharmonic approximation 23,24 show that the band evolution cannot be fully captured by the temperature-induced volume change. Using ab initio molecular dynamics (AIMD) and taking snapshots of structures for band calculations, Kim et al 25 found that the L and Σ pockets converged at 450 K. The results of Gibbs et al 26 further supported to the twofold contribution (lattice expansion and atomic displacement) to the L-Σ convergence, with the converged temperature was 700 K for PbTe. Generally speaking, the mechanism of temperature-induced band convergence is at the stage of rationalisation and more efforts are needed to get a better understanding of the phenomenon.…”

Section: Electrical Transport In Thermoelectricsmentioning

confidence: 50%

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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Effect of thermal disorder on high figure of merit in PbTe

Cited by 46 publications

References 47 publications

Valleytronics in thermoelectric materials

Valleytronics in thermoelectric materials

Intrinsic low thermal conductivity in weakly ionic rocksalt structures

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

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