Thermoelectric transport effects beyond single parabolic band and acoustic phonon scattering

Wang, Heng; Gurunathan, Ramya; Fu, Chenguang; Cui, R.; Zhu, Tiejun; Snyder, G. Jeffrey

doi:10.1039/d1ma00780g

Cited by 25 publications

(22 citation statements)

References 196 publications

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“…The simplest approach is to use a linear fit of either ρ(T) or µ(T) on logarithmic axes in order to determine the temperature exponent. Another approach uses band modelling to fit the n H dependence of µ H at fixed temperature, with Matthiessen's rule used to balance contributions of APS and AS, although this is difficult as both have identical n H dependence [14,15,17]. Direct fitting of ρ(T) is most commonly seen in low-temperature data using the Bloch-Grüneisen model in highly metallic samples [18,19], with APS as the dominant scattering mechanism.…”

Section: Introductionmentioning

confidence: 99%

Electronic scattering in half-Heusler thermoelectrics from resistivity data

2022

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A key part of optimising thermoelectric materials is understanding the electronic scattering mechanism. For half-Heusler thermoelectrics, the dominant mechanisms are acoustic phonon scattering in pure systems and alloy scattering in highly alloyed systems. In this report, the significance of the residual resistivity ρ0 is highlighted. Large ρ0 values can lead to misidentification of the dominant scattering mechanism when only high-temperature ρ(T) data is available. A straightforward approach to analyse ρ(T) is proposed and applied to a range of HH systems. This reveals large levels of structural disorder in XIVNiSn, whilst XVFeSb has the strongest coupling with acoustic phonons. The electronic scattering mechanism depends sensitively on composition, with acoustic (∝T1.5), metallic (∝T1) and alloy (∝T0.5) scattering observed within the main families of half-Heusler compounds. With the aid of velocity of sound, band mass and carrier concentration data, the deformation potential can be obtained, enabling quantification of the interaction between phonons and carriers, from fits to resistivity data. This work provides a route for the analysis of experimental ρ(T) data that can be applied to a range of thermoelectric materials.

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Section: Introductionmentioning

confidence: 99%

Electronic scattering in half-Heusler thermoelectrics from resistivity data

2022

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“…The deformation potential we calculated from the experimental data demonstrated that Cl doping reduced the deformation potential of n-type SnSe crystals enormously—that is, from ~22.4 eV in SnSe-Br to ~17.5 eV in SnSe-Cl—and was therefore responsible for the improved μ H . The increase in deformation potential after Pb alloying was primarily the result of the enhanced valley degeneracy and alloy scattering potential ( 32 , 35 ). Nevertheless, the deformation potential decreased with increasing Pb content and reduced to ~17 eV at 10% Pb alloying, which implies that underlying mechanisms compensated for the detrimental effect of enhanced valley degeneracy and alloy scattering potential.…”

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confidence: 99%

High thermoelectric performance realized through manipulating layered phonon-electron decoupling

Wang

et al. 2022

Science

256

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Thermoelectric materials allow for direct conversion between heat and electricity, offering the potential for power generation. The average dimensionless figure of merit ZT ave determines device efficiency. N-type tin selenide crystals exhibit outstanding three-dimensional charge and two-dimensional phonon transport along the out-of-plane direction, contributing to a high maximum figure of merit Z max of ~3.6 × 10 −3 per kelvin but a moderate ZT ave of ~1.1. We found an attractive high Z max of ~4.1 × 10 −3 per kelvin at 748 kelvin and a ZT ave of ~1.7 at 300 to 773 kelvin in chlorine-doped and lead-alloyed tin selenide crystals by phonon-electron decoupling. The chlorine-induced low deformation potential improved the carrier mobility. The lead-induced mass and strain fluctuations reduced the lattice thermal conductivity. Phonon-electron decoupling plays a critical role to achieve high-performance thermoelectrics.

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“…even though a single band model cannot describe all transport details realistically. A single band is, of course, not enough to capture the complete picture of the material when more than one majority carrier band [26][27][28] and/or minority carrier bands are contributing substantially to charge transport. Particularly, the minority carrier density scales roughly with exp ( −E g /2k B T ) and the band gap itself decreases with increasing temperature for most materials [29,30].…”

Section: Introductionmentioning

confidence: 99%

Developing a two-parabolic band model for thermoelectric transport modelling using Mg₂Sn as an example

2022

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Thermoelectrics is a field driven by material research aimed at increasing the thermal to electrical conversion efficiency of thermoelectric (TE) materials. Material optimisation is necessary to achieve a high figure of merit (zT) and in turn a high conversion efficiency. Experimental efforts are guided by the theoretical predictions of the optimum carrier concentration for which generally the Single Parabolic Band (SPB) model is used which considers the contribution to electronic transport only from the majority carriers’ band. However, most TE materials reach peak performance (maximum zT) close to their maximum application temperature and when minority carrier effects become relevant. Therefore, single band modelling is insufficient to model the behaviour of TE materials in their most practically relevant temperature range. Inclusion of minority effects requires addition of the minority carrier band and necessitates the use of a two-band model – the simplest and, for most cases, sufficient improvement. In this study, we present a systematic methodology for developing a two-band model using one valence and one conduction band for any TE material. The method utilises the SPB model and a simple cost function-based analysis to extract material parameters like density of states masses, band gap, deformation potential constant etc., based on easily available experimental data. This simple and powerful method is exemplified using Mg2Sn (an end member of the highly popular Mg2(Si,Sn) solid solutions), chosen due to its low band gap and the availability of experimental data in a wide range of dopant concentrations. Using the experimental data for p- and n-type Mg2Sn from literature, a two-band model was obtained and optimum carrier concentration and maximum zT were predicted. At 650 K, pronounced differences between the SPB and the two-band model, which could prevent realisation of maximum zT, were observed demonstrating the practical necessity to model the effect of minority carriers.

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Thermoelectric transport effects beyond single parabolic band and acoustic phonon scattering

Abstract: Thermoelectric materials have been extensively studied for applications in solid-state power generation and cooling. Progress has been made over the past decade in multiple materials systems, hence, it becomes increasingly...

Cited by 25 publications

References 196 publications

Electronic scattering in half-Heusler thermoelectrics from resistivity data

Electronic scattering in half-Heusler thermoelectrics from resistivity data

High thermoelectric performance realized through manipulating layered phonon-electron decoupling

Developing a two-parabolic band model for thermoelectric transport modelling using Mg₂Sn as an example

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Thermoelectric transport effects beyond single parabolic band and acoustic phonon scattering

Abstract: Thermoelectric materials have been extensively studied for applications in solid-state power generation and cooling. Progress has been made over the past decade in multiple materials systems, hence, it becomes increasingly...

Cited by 25 publications

References 196 publications

Electronic scattering in half-Heusler thermoelectrics from resistivity data

Electronic scattering in half-Heusler thermoelectrics from resistivity data

High thermoelectric performance realized through manipulating layered phonon-electron decoupling

Developing a two-parabolic band model for thermoelectric transport modelling using Mg2Sn as an example

Contact Info

Product

Resources

About

Developing a two-parabolic band model for thermoelectric transport modelling using Mg₂Sn as an example