α-Bi2Sn2O7: a potential room temperature n-type oxide thermoelectric

Rahim, Warda; Skelton, Jonathan M.; Scanlon, David O.

doi:10.1039/d0ta03945d

Cited by 25 publications

(27 citation statements)

References 110 publications

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“…22,23 Recently, we reported the promising thermoelectric properties of the room temperature polymorph of Bi 2 Sn 2 O 7 , which we found to have an ultralow intrinsic lattice thermal conductivity of $0.4 W m À1 K À1 and a ZT of 0.18 with ntype doping. 24 Although this ZT is the highest ever obtained for an oxide material at room temperature, Bi 2 Sn 2 O 7 may not be suitable for high-temperature applications as it undergoes a phase transition above 390 K.…”

Section: Introductionmentioning

confidence: 92%

Ca4Sb2O and Ca4Bi2O: Two Promising Mixed-Anion Thermoelectrics

Rahim¹,

Skelton²,

Scanlon³

2021

Preprint

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<pre>The environmental burden of fossil fuels and the rising impact of global warming have created an urgent need for sustainable clean energy sources. This has led to widespread interest in thermoelectric (TE) materials to recover part of the 60 % of global energy currently wasted as heat as usable electricity. Oxides are particularly attractive as they are thermally stable, chemically inert, and formed of earth-abundant elements, but despite intensive efforts there have been no reports of oxide TEs matching the performance of flagship chalcogenide materials such as PbTe, Bi2Te3 and SnSe. A number of ternary X4Y2Z mixed-anion systems, including oxides, have predicted band gaps in the useful range for several renewable-energy applications, including as TEs, and some also show the complex crystal structures indicative of low lattice thermal conductivity. In this study, we use ab initio calculations to investigate the TE performance of two structurally-similar mixed-anion oxypnictides, Ca4Sb2O and Ca4Bi2O. Electronic-structure and band-alignment calculations using hybrid density-functional theory (DFT), including spin-orbit coupling, suggest that both materials are likely to be p-type dopable with large charge-carrier mobilities. Lattice-dynamics calculations using third-order perturbation theory predict ultra-low lattice thermal conductivities of about 0.8 and 0.5 W m-1 K-1 above 750 K. Nanostructuring to a crystal grain size of 20 nm is predicted to further reduce the room temperature thermal conductivity by around 40 %. Finally, we use the electronic- and thermal-transport calculations to estimate the thermoelectric figure of merit ZT, and show that with p-type doping both oxides could potentially serve as promising earth-abundant oxide TEs for high-temperature applications.</pre>

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Section: Introductionmentioning

confidence: 92%

Ca4Sb2O and Ca4Bi2O: Two Promising Mixed-Anion Thermoelectrics

Rahim¹,

Skelton²,

Scanlon³

2021

Preprint

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“…[27] First-principles modelling of the structural dynamics and thermal transport, typically using densityfunctional theory (DFT), has been instrumental in understanding the intrinsically low latt of flagship thermoelectric and other highly-anharmonic materials, [28][29][30][31][32] and has also been applied to identify novel candidate TEs. [33][34][35] Despite a large body of experimental work on the skutterudites, there are comparatively few modelling studies on the phonon thermal transport. [36][37][38][39][40] Such studies could provide valuable insight into the underlying microscopic mechanisms by which doping and filling reduce the latt and direct future work to identify and optimise novel high-performance skutterudite TEs.…”

Section: Introductionmentioning

confidence: 99%

Impact of noble-gas filler atoms on the lattice thermal conductivity of CoSb₃ skutterudites: first-principles modelling

Tang

Skelton

2021

J. Phys.: Condens. Matter

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We present a systematic first-principles modelling study of the structural dynamics and thermal transport in the CoSb3 skutterudites with a series of noble-gas filler atoms. A range of analysis techniques are proposed to estimate the filler rattling frequencies, to quantify the separate impacts of filling on the phonon group velocities and lifetimes, and to show how changes to the phonon spectra and interaction strengths lead to suppressed lifetimes. The fillers are found to reduce the thermal conductivity of the CoSb3 framework by up to 15 % primarily by suppressing the group velocities of low-lying optic modes. Calculations show that the filler rattling frequencies are determined by a detailed balance of increasing atomic mass and stronger interactions with the framework, and are a good predictor of their impact on the heat transport. Lowering the rattling frequency below ~1.5 THz by selecting heavy fillers that interact weakly with the framework is predicted to produce a much larger suppression of the thermal transport, by inducing avoided crossings in the acoustic-mode dispersion and facilitating resonant scattering with a consequent large reduction in the lifetimes. Approximate rattling frequencies determined from the harmonic force constants may therefore provide a useful metric for selecting filler atoms to optimise the thermal transport in skutterudites and other cage compounds such as clathrates.

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“…In particular, it has recently become feasible to accurately model lattice dynamics 29 and thermal transport, [30][31][32] and insight from studying highlyanharmonic materials is helping to establish structure/property relationships for identifying new highperformance TEs and optimising the performance of existing materials. 23,24,33,34 More recently, highthroughput modelling studies have been applied to identify potentially promising but previouslyoverlooked TEs from known materials. [35][36][37] However, the inherent difficulty of modelling solid solutions means that comparatively little modelling work has been done to understand the impact of alloying on thermoelectric properties.…”

Section: Introductionmentioning

confidence: 99%

Approximate Models for the Lattice Thermal Conductivity of Alloy Thermoelectrics

Skelton¹

2021

Preprint

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Thermoelectric generators (TEGs) convert waste heat to electricity and are a leading contender for improving energy efficiency at a range of scales. Ideal TE materials show a large Seebeck effect, high electrical conductivity, and low thermal conductivity. Alloying is a widely-used approach to engineering the heat transport in TEs, but despite many successes the underlying mechanisms are poorly understood. In previous work, first-principles modelling has successfully been used to study the thermodynamics of alloy formation and to investigate its effect on the electronic structure and phonon spectrum. However, it has so far only been possible to examine qualitatively the impact of alloying on the lattice thermal conductivity. In this work, we develop and test two new approaches to addressing this. The constant relaxation-time approximation (CRTA) assumes the primary effect of alloying is on the phonon group velocities, and allows the thermal conductivity to be calculated assuming a suitable constant lifetime. Alternatively, setting the three-phonon interaction strengths to a constant further enables an assessment of how changes to the phonon frequency spectrum influence the lifetimes. We test both approaches for the Pnma Sn(S1-xSex) alloy system and are able to account for the substantially-reduced thermal conductivity measured in experiments.

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α-Bi₂Sn₂O₇: a potential room temperature n-type oxide thermoelectric

Abstract: Using ab initio methods, we predict α-Bi2Sn2O7 to have an ultra-low lattice thermal conductivity at room temperature due to the high density of phonon scattering events, which makes it a potential earth-abundant n-type low temperature thermoelectric.

Cited by 25 publications

References 110 publications

Ca4Sb2O and Ca4Bi2O: Two Promising Mixed-Anion Thermoelectrics

Ca4Sb2O and Ca4Bi2O: Two Promising Mixed-Anion Thermoelectrics

Impact of noble-gas filler atoms on the lattice thermal conductivity of CoSb₃ skutterudites: first-principles modelling

Approximate Models for the Lattice Thermal Conductivity of Alloy Thermoelectrics

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α-Bi2Sn2O7: a potential room temperature n-type oxide thermoelectric

Abstract: Using ab initio methods, we predict α-Bi2Sn2O7 to have an ultra-low lattice thermal conductivity at room temperature due to the high density of phonon scattering events, which makes it a potential earth-abundant n-type low temperature thermoelectric.

Cited by 25 publications

References 110 publications

Ca4Sb2O and Ca4Bi2O: Two Promising Mixed-Anion Thermoelectrics

Ca4Sb2O and Ca4Bi2O: Two Promising Mixed-Anion Thermoelectrics

Impact of noble-gas filler atoms on the lattice thermal conductivity of CoSb3 skutterudites: first-principles modelling

Approximate Models for the Lattice Thermal Conductivity of Alloy Thermoelectrics

Contact Info

Product

Resources

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α-Bi₂Sn₂O₇: a potential room temperature n-type oxide thermoelectric

Impact of noble-gas filler atoms on the lattice thermal conductivity of CoSb₃ skutterudites: first-principles modelling