Approximate models for the lattice thermal conductivity of alloy thermoelectrics

Skelton, Jonathan M.

doi:10.1039/d1tc02026a

Cited by 23 publications

(81 citation statements)

References 58 publications

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“…As for latt the CRTA ⁄ are tensors, and the CRTA may be taken as a scalar, like the , or as a tensor to provide some flexibility to account for anisotropy in the averaged mode lifetimes. 46,70 Table 5 Constant relaxation-time approximation (CRTA) analysis of the room-temperature averaged thermal conductivities ave of Bi2S3, Bi2Se3 and Bi2Te3 in the Pnma and R3 ̅ m phases according to Eq. 7 in the text.…”

Section: Resultsmentioning

confidence: 99%

“…variance model. 46 Although the predictions in the previous section indicate that Bi2(Se0.55S0.45) would adopt the Pnma structure, the steep decrease in latt with S content for 0 < < 0.1 suggests that alloying with a small amount of S may be beneficial to reducing the latt of R3 ̅ m Bi2Se3.…”

Section: Thermodynamics Of Binary Solid Solutions Based On the Relative Energies Of The Pnmamentioning

confidence: 85%

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Structural Dynamics and Thermal Transport in Bismuth Chalcogenide Alloys

Cen

Pallikara

Skelton

2021

Preprint

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We present a detailed study of the structural dynamics, energetic and dynamical stability and thermal transport of the bismuth chalcogenides Bi2S3, Bi2Se3 and Bi2Te3 and their alloys. The differing activities of the Bi cation lone pairs in Bi2S3, Bi2Se3 and Bi2Te3 lead to competition between orthorhombic Pnma and rhombohedral R3 ̅ m phases, with the latter favored by heavier chalcogen atoms, while the reported non-ambient phases of Bi2Se3 and Bi2Te3 show phonon instabilities under ambient conditions. The Pnma structure has weaker chemical bonding and stronger phonon anharmonicity than the R3 ̅ m phase, resulting in an intrinsically lower lattice thermal conductivity. A thermodynamic model of Bi2(Se1-xSx)3 indicates that the R3 ̅ m structure is energetically favored only for low S content, but the stability window can potentially be extended at lower formation temperatures. Bi2(Se1-xTex)3 in the R3 ̅ m phase shows substantial deviation from ideal solid-solution behavior, due to a strong energetic preference for the Se and Te atoms to occupy the interior and exterior sites, respectively, in the constituent quintuple layers. Strain-field fluctuations induced by inhomogeneities in the chemical bonding are shown to play a significant role in determining the heat transport in the alloy systems, and chalcogen disorder away from the preferred symmetric structure is found to be an important factor in the reduced thermal conductivity of Bi2SeTe2 compared to the Bi2Te3 endpoint. The microscopic insight from these modelling studies provides new insight into the bismuth chalcogenides and their alloys, which may inform ongoing research to optimize the thermoelectric performance of these and related materials.

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Section: Resultsmentioning

confidence: 99%

Section: Thermodynamics Of Binary Solid Solutions Based On the Relative Energies Of The Pnmamentioning

confidence: 85%

Structural Dynamics and Thermal Transport in Bismuth Chalcogenide Alloys

Cen

Pallikara

Skelton

2021

Preprint

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“…To better understand the origin of the trends in the 𝜅 latt , we use the constant relaxationtime approximation (CRTA) model developed in our previous work. 46,70 We write the 𝜿 latt as the product of a temperature-dependent harmonic function 𝜿 𝜏 CRTA ⁄ and weighted average lifetime 𝜏 CRTA defined according to:…”

Section: Resultsmentioning

confidence: 99%

“…44,45 The structure, properties and energetic and dynamical stability of different compositions can be evaluated in silico, providing a means to predict the electronic structure and thermal transport of the alloy and to guide experimental design towards optimizing the properties for thermoelectric applications. [44][45][46] The high computational resource requirements for modelling the lattice dynamics and thermal transport, however, pose significant challenges to studying alloy systems this way, which has resulted in few investigations in this direction. 42,[44][45][46][47][48] In this work, we use first-principles DFT calculations to perform a comprehensive study of the lattice dynamics, energetic and dynamical stability and thermal transport of all of the reported phases of Bi2S3, Bi2Se3 and Bi2Te3, and we employ methodology developed in previous studies to investigate the thermodynamics and properties of Bi2(Se,S)3 and Bi2(Se,Te)3 alloys.…”

Section: 𝑍𝑇 =mentioning

confidence: 99%

“…[44][45][46] The high computational resource requirements for modelling the lattice dynamics and thermal transport, however, pose significant challenges to studying alloy systems this way, which has resulted in few investigations in this direction. 42,[44][45][46][47][48] In this work, we use first-principles DFT calculations to perform a comprehensive study of the lattice dynamics, energetic and dynamical stability and thermal transport of all of the reported phases of Bi2S3, Bi2Se3 and Bi2Te3, and we employ methodology developed in previous studies to investigate the thermodynamics and properties of Bi2(Se,S)3 and Bi2(Se,Te)3 alloys. The differing activities of the Bi cation lone pairs in Bi2S3, Bi2Se3 and Bi2Te3 lead to competition between R3 ̅ m and Pnma phases with very different thermal transport properties, which we attribute quantitatively to differences in the phonon group velocities and lifetimes.…”

Section: 𝑍𝑇 =mentioning

confidence: 99%

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Structural Dynamics and Thermal Transport in Bismuth Chalcogenide Alloys

Cen

Pallikara

Skelton

2021

Preprint

Self Cite

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We present a detailed study of the structural dynamics, energetic and dynamical stability and thermal transport of the bismuth chalcogenides Bi2S3, Bi2Se3 and Bi2Te3 and their alloys. The differing activities of the Bi cation lone pairs in Bi2S3, Bi2Se3 and Bi2Te3 lead to competition between orthorhombic Pnma and rhombohedral R-3m phases, with the latter favored by heavier chalcogen atoms, while the reported non-ambient phases of Bi2Se3 and Bi2Te3 show phonon instabilities under ambient conditions. The Pnma structure has weaker chemical bonding and stronger phonon anharmonicity than the R-3m phase, resulting in an intrinsically lower lattice thermal conductivity. A thermodynamic model of Bi2[Se(1-x)S(x)]3 indicates that the R-3m structure is energetically favored only for low S content, but the stability window can potentially be extended at lower formation temperatures. Bi2[Se(1-x)Te(x)]3 in the R-3m phase shows substantial deviation from ideal solid-solution behavior, due to a strong energetic preference for the Se and Te atoms to occupy the interior and exterior sites, respectively, in the constituent quintuple layers. Strain-field fluctuations induced by inhomogeneities in the chemical bonding are shown to play a significant role in determining the heat transport in the alloy systems, and chalcogen disorder away from the preferred symmetric structure is found to be an important factor in the reduced thermal conductivity of Bi2SeTe2 compared to the Bi2Te3 endpoint. The microscopic insight from these modelling studies provides new insight into the bismuth chalcogenides and their alloys, which may inform ongoing research to optimize the thermoelectric performance of these and related materials.

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