Lattice instabilities and phonon thermal transport in TlBr

Pandey, Tribhuwan; Lindsay, Lucas; Sales, B. C.; Parker, David

doi:10.1103/physrevmaterials.4.045403

Cited by 10 publications

(8 citation statements)

References 61 publications

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“…Nonzero off-diagonal BECs are observed for the Pnmn phase, which indicates that the BECs are not only from nearest-neighbor distances but also are strongly influenced by next-nearest-neighbor interactions in the highly distorted Pnmn phase . Enhanced BECs result in large LO–TO splitting, which brings the lattice (TO modes) in proximity to ferroelectric instability and lowers κ l . Therefore, it is very intriguing to investigate the elastic and phonon transport properties of stereochemically active lone pair materials under hydrostatic compression in general and in particular for Bi 2 O 2 S.…”

Section: Resultsmentioning

confidence: 99%

“…58 Enhanced BECs result in large LO−TO splitting, which brings the lattice (TO modes) in proximity to ferroelectric instability 57 and lowers κ l . 59 Therefore, it is very intriguing to investigate the elastic and phonon transport properties of stereochemically active lone pair materials under Mechanical and Dynamic Stability. To explore the mechanical and dynamic stability, we calculated the secondorder elastic constants (SOECs) and phonon dispersion curves, respectively, for the Pnmn and I4/mmm phases of Bi 2 O 2 S at ambient as well as at high pressure.…”

Section: ■ Computational Details and Methodologymentioning

confidence: 99%

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Effect of Hydrostatic Pressure on Lone Pair Activity and Phonon Transport in Bi₂O₂S

Yedukondalu

Pandey

Roshan

2023

ACS Appl. Energy Mater.

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Dibismuth dioxychalcogenides, Bi 2 O 2 Ch (Ch = S, Se, Te), are a promising class of materials for next-generation electronics and thermoelectrics due to their ultrahigh carrier mobility and excellent air stability. An interesting member of this family is Bi 2 O 2 S, which has a stereochemically active 6s 2 lone pair of Bi 3+ cations, heterogeneous bonding, and a high mass contrast between its constituent elements. In the present study, we have used first-principles calculations in combination with Boltzmann transport theory to systematically investigate the effect of hydrostatic pressure on lattice dynamics and phonon transport properties of Bi 2 O 2 S. We found that the ambient Pnmn phase has a low average lattice thermal conductivity (κ l ) of 1.71 W/(m K) at 300 K. We also predicted that Bi 2 O 2 S undergoes a structural phase transition from a low-symmetry (Pnmn) to a high-symmetry (I4/mmm) structure at around 4 GPa due to centering of Bi 3+ cations with pressure. Upon compression, the lone pair activity of Bi 3+ cations is suppressed, which increases κ l by almost 3 times to 4.92 W/ (m K) at 5 GPa for the I4/mmm phase. The computed phonon lifetimes and Gruneisen parameters show that anharmonicity decreases with increasing pressure due to further suppression of the lone pair activity and strengthening of intra-and intermolecular interactions, leading to an average room-temperature κ l of 12.82 W/(m K) at 20 GPa. Overall, this study provides a comprehensive understanding of the effect of hydrostatic pressure on the stereochemical activity of the lone pair of Bi 3+ cations and its implications on the phonon transport properties of Bi 2 O 2 S.

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Section: Resultsmentioning

confidence: 99%

Section: ■ Computational Details and Methodologymentioning

confidence: 99%

Effect of Hydrostatic Pressure on Lone Pair Activity and Phonon Transport in Bi₂O₂S

Yedukondalu

Pandey

Roshan

2023

ACS Appl. Energy Mater.

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“…Thermoelectric (TE) material, despite being promising as a potential candidate to convert waste heat to electricity and vice versa, is still mostly used for niche applications like spacecraft and the defense industry [1,2]. Strong coupling among intrinsic material properties like the Seebeck coefficient (S), electrical resistivity (ρ), and the electronic component of thermal conductivity (κ e ) via carrier concentration (n H ) makes it challenging to obtain TE material of high efficiency, defined by the dimensionless figure of merit ZT = S 2 T /ρκ, where T is the absolute temperature, κ (= κ e + κ L ) is the thermal conductivity, and a significant part of κ originates from lattice contribution (κ L ) [1][2][3]. In recent times, two main strategies have generally been adopted for increasing ZT : one is to decouple these parameters to increase the power factor (PF = S 2 /ρ) by band engineering which includes band distortion [4], band convergence [5,6], band nestification [7], and the other involving efforts to reduce κ L by phonon engineering [8].…”

Section: Introductionmentioning

confidence: 99%

Improvement of thermoelectric performance in Sb2Te3/Te composites

Das

Singha

Daou

et al. 2022

Phys. Rev. Materials

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Te-impurity-incorporated Sb 2 Te 3 , i.e., Sb 2 Te 3 + x mol % Te (x = 0, 4, 6, and 9) composites were synthesized by solid-state reaction technique. Analysis of x-ray diffraction indicates not only Te impurity as a second phase but also doping of Te via suppression of inherent Te vacancies in the Sb 2 Te 3 matrix. As a result of this doping and of the change in formation energy of different types of native defects in Sb 2 Te 3 due to synthesis in a Te-rich condition, carrier concentration (n H ) lower than the pristine sample was observed. Low n H along with gradual convergence of valence bands due to progressive suppression of Te vacancies increases the Seebeck coefficient (S) in Te-incorporated samples. Even though Te impurities increase electrical resistivity (ρ), enhanced texturing of lattice planes ensures that charge carrier mobility does not degrade due to Te addition. As a result, a maximum power factor = 17 μW cm −1 K −2 at T = 480 K for x = 6 has been achieved. In addition, Te addition strengthens phonon scattering via an increase of phonon-phonon Umklapp scattering and point-defect-induced scattering of phonons. Due to such a strong phonon scattering, thermal conductivity (κ) decreases, and a reduced lattice thermal conductivity (κ L ), as low as 0.28 W m −1 K −1 at 500 K for x = 6, has been achieved. As a result of simultaneous increase of S and decrease of κ, a high ZT ∼0.87 at 480 K, almost 33% higher than that of the host material, has been achieved.

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“…Enhanced BECs bring the lattice in the proximity of ferroelectric instability 45 thereby lowering the lattice thermal conductivity (κ l ). 47 Therefore, it is very intriguing to investigate elastic and phonon transport properties of lone-pair containing materials in general and in particular for Bi 2 O 2 S, especially to understand what is the effect of lone-pair on lattice dynamics and phonon transport at high pressure?…”

Section: Cross-band-gap Hybridization and Enhanced Born Effective Cha...mentioning

confidence: 99%

Effect of hydrostatic pressure on stereochemically active lone-pair of Bi$_2$O$_2$S

Yedukondalu¹,

Pandey²,

Roshan³

2022

Preprint

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Dibismuth dioxychalcogenides, Bi 2 O 2 Ch (Ch = S, Se, Te) are emerging class of materials for the next generation electronics and thermoelectrics with an ultrahigh carrier mobility and excellent air stability. These are layered materials with weak electrostatic interlayer interactions which makes them unique compared to layered materials with weak interlayer van der Waals bonding. In particular, Bi 2 O 2 S is fascinating because of stereo-chemically active 6s 2 lone-pair of Bi 3+ cation, heterogeneous bonding and high mass contrast. Understanding the effect of hydrostatic pressure on lone-pair and its implications on phonon transport have attracted enormous research interest recently. In the present work, we systematically investigated the high pressure behavior of Bi 2 O 2 S, it undergoes a structural phase transition from low symmetry (P nmn) to a high symmetry (I4/mmm) structure around 4 GPa. Pressure dependent static enthalpy, lattice, bond parameters and elastic constants strongly suggest that the phase transition is continuous. Enhanced Born effective charges (BECs) are predicted for both the phases due to significant cross-band-gap hybridization from their electronic structure. This brings the lattice in the vicinity of ferroelectric instability, which is favorable to achieve low κ l in Bi 2 O 2 S. The obtained low κ l value 1.47 W-m/K for P nmn phase is more than double 3.63 W-m/K for I4/mmm phase, which is due to suppression of lone-pair at Bi 3+ cation, consequently, anharmonicity diminishes with pressure as shown from electron localization function, potential energy surfaces and mean square atomic displacements. Overall, the current study provides an in depth understanding on how hydrostatic pressure effects the phonon transport in stereo-chemically active 6s 2 lone-pair containing Bi 2 O 2 S through a continuous structural phase transition.

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Lattice instabilities and phonon thermal transport in TlBr

Cited by 10 publications

References 61 publications

Effect of Hydrostatic Pressure on Lone Pair Activity and Phonon Transport in Bi₂O₂S

Effect of Hydrostatic Pressure on Lone Pair Activity and Phonon Transport in Bi₂O₂S

Improvement of thermoelectric performance in Sb2Te3/Te composites

Effect of hydrostatic pressure on stereochemically active lone-pair of Bi$_2$O$_2$S

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Lattice instabilities and phonon thermal transport in TlBr

Cited by 10 publications

References 61 publications

Effect of Hydrostatic Pressure on Lone Pair Activity and Phonon Transport in Bi2O2S

Effect of Hydrostatic Pressure on Lone Pair Activity and Phonon Transport in Bi2O2S

Improvement of thermoelectric performance in Sb2Te3/Te composites

Effect of hydrostatic pressure on stereochemically active lone-pair of Bi$_2$O$_2$S

Contact Info

Product

Resources

About

Effect of Hydrostatic Pressure on Lone Pair Activity and Phonon Transport in Bi₂O₂S

Effect of Hydrostatic Pressure on Lone Pair Activity and Phonon Transport in Bi₂O₂S