Search query: high performance thermoelectrics

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abstract: Summary We introduce Sb2Si2Te6 as a high performance thermoelectric material. Single crystal X ray diffraction analysis indicates that Sb2Si2Te6 has a layered two dimensional structure with Sb3+ cations and [Si2Te6]6 units as building blocks adopting the Fe2P2Se6 structure type. Sb2Si2Te6 is a direct band gap semiconductor with valence band maximum and conduction band minimum at the Z point in the Brillouin zone, where the band is doubly degenerate. Polycrystalline bulk pellets of Sb2Si2Te6 with randomly packed grains exhibit an intrinsically high thermoelectric figure of merit ZT of ~1.08 at 823 K. We then create a cellular nanostructure with ultrathin Si2Te3 nanosheets covering the Sb2Si2Te6 grains, which act as a hole transmitting electron blocking filter and at the same time cause extra phonon scattering. This dual function of the cellular nanostructure achieves an ultralow thermal conductivity value of ~0.29 Wm 1K 1 and a high ZT value of ~1.65 at 823 K for Sb2Si2Te6, along with a high average ZT value of ~0.98.
author_names: Yubo Luo

Songting Cai

Shiqiang Hao

Florian Pielnhofer

Ido Hadar

Zhong-Zhen Luo

Jianwei Xu

Christopher Wolverton

Vinayak P Dravid

Arno Pfitzner

Qingyu Yan

Mercouri G Kanatzidis
title: High Performance Thermoelectrics from Cellular Nanostructured Sb2Si2Te6
year: 2020

abstract: Thermoelectric energy conversion from waste heat sources is expected to play a crucial role in determining the world energy landscape through efficient thermal energy utilization and management. The thermoelectric performance of a material critically depends on its electrical conductivity and Seebeck coefficient. The electronic structure plays a pivotal role in determining both these parameters, electrical conductivity and Seebeck coefficient, in a material and, therefore, in turn, dominantly controls the material's thermoelectric performance. For example, a common feature among most of the known high performance thermoelectric materials is that they are heavily doped degenerate semiconductors and have large band degeneracy. Therefore, it is essential to improve our understanding and manipulation capabilities of the electronic structure in a material. Intensive research on thermoelectric materials has led to various novel electronic structure modulation strategies, such as valence band convergence, resonant level, and employment of various low dimensional electronic features. These strategies play a critical role in the recent developments of various high performance thermoelectric materials, such as PbTe, SnTe, SnSe, and GeTe. In this Perspective, we have discussed various electronic structure modulation strategies and their recent developments with a brief background of the underlying ideas.
author_names: Moinak Dutta

Tanmoy Ghosh

Kanishka Biswas
title: Electronic structure modulation strategies in high performance thermoelectrics
year: 2020

abstract: Abstract Thermoelectric materials with efficient heat energy conversion have been widely considered as potential electrical energy sources. Herein we propose an anion exchanged porous SnTe nanosheets (NSs) as a high performance thermoelectric material with ultra low thermal conductivity. The solution phase reaction mechanisms for porous SnTe NSs are proposed, and the reaction conditions are carefully manipulated in order to determine the optimal morphology and excellent thermoelectric performance. The porous SnTe NSs, which consist of extremely small nanoparticles of only ~3 nm in size with defective shapes, lead to a substantial reduction in the lattice thermal conductivity and a higher Seebeck coefficient compared to bulk SnTe, caused by the introduced nanointerfaces, pores and defects. An impressive ZT of ~1.1 at 923 K is achieved without atomic doping process, which is as many as ~2.8 times higher than that of bulk SnTe. This proposed strategy provides an insight to represent an unconventional method for the production of the porous SnTe NSs that can potentially be employed in practical high performance thermoelectric applications.
author_names: Hyun Ju

Jooheon Kim
title: Anion exchanged porous SnTe nanosheets for ultra low thermal conductivity and high performance thermoelectrics
year: 2020

abstract: This review discusses recent developments and current research in high performance bulk thermoelectric materials, comprising nanostructuring, mesostructuring, band alignment, band engineering and synergistically defining key strategies for boosting the thermoelectric performance. To date, the dramatic enhancements in the figure of merit achieved in bulk thermoelectric materials have come either from the reduction in lattice thermal conductivity or improvement in power factors, or both of them. Here, we summarize these relationships between very large reduction of the lattice thermal conductivity with all scale hierarchical architecturing, large enhanced Seebeck coefficients with intra matrix electronic structure engineering, and control of the carrier mobility with matrix/inclusion band alignment, which enhance the power factor and reduce the lattice thermal conductivity. The new concept of hierarchical compositionally alloyed nanostructures to achieve these effects is presented. Systems based on PbTe, PbSe and PbS in which spectacular advances have been demonstrated are given particular emphasis. A discussion of future possible strategies is aimed at enhancing the thermoelectric figure of merit of these materials.
author_names: Li-dong Zhao

Vinayak P Dravid

Mercouri G Kanatzidis
title: The panoscopic approach to high performance thermoelectrics
year: 2014

abstract: Abstract The search for new thermoelectric materials has been of great interest in recent years because thermoelectrics offers useful applications in next generation vehicles that can directly convert waste heat to electricity. Two dimensional (2D) tetradymites with M2X3 compounds, in which M (Bi) and X (Te, Se, S) are a group V metal and group VI anion, respectivety, are theoretically investigated in this study. Their energy bands are characterized by small energy gaps, high group velocities, small effective masses, nonparabolic bands and multi valleys convergence at near the center of the Brillouin zone, which are favorable conditions for high power factor with the optimum power factor values can be up to 0.20 0.25 W/mK2 at room temperature. Moreover, the 2D M2X3 contains heavy atomic masses and high polarizability of some chemical bonds, leading to small group velocities of phonons and anharmonic phonon behavior that produce an intrinsic lattice thermal conductivity as low as 1.5 2.0 W/mK at room temperature. We find that by mixtures of M and X atoms, such as Bi2Te2Se, the power factor further increases whereas the lattice thermal conductivity decreases. This design gives a high figure of merit of the p type 2D Bi2Te2Se from 1.4 to 2.0 at operating temperature within 300 500 K.
author_names: Nguyen Tuan Hung

Ahmad Ridwan Tresna Nugraha

Riichiro Saito
title: Designing high performance thermoelectrics in two dimensional tetradymites
venue: Nano Energy
year: 2019

abstract: Lead chalcogenides and their alloys belong at the heart of thermoelectrics due to their large thermoelectric figure of merit (zT) However, recent research has shown a limitation in the use of lead (Pb) based materials due to their toxicity and efforts have been made to produce non toxic analogues of lead chalcogenides. Tin chalcogenides have been predicted to be promising for this purpose due to their unique electronic structure and phonon dispersion properties. Here, we discuss the journey of tin chalcogenides in the field of thermoelectrics and topological materials with the main emphasis on the bonding, crystal structures, electronic band structures, phonon dispersion and thermoelectric properties. The thermal transport properties of tin chalcogenides are explained based on lattice dynamics, where resonant bonding and local structural distortion play an important role in creating lattice anharmonicity, thereby lowering the lattice thermal conductivity. Since thermoelectric and topological materials, especially topological insulators and topological crystalline insulators, share similar material features, such as a narrow band gap, heavy constituent elements and significant spin orbit coupling, we have discussed the thermoelectric properties of several topological tin chalcogenides from a chemistry perspective. This feature article serves as a useful reference for researchers who strive to improve the properties of tin chalcogenides and advance the field of thermoelectric and topological materials.
author_names: Ananya Banik

Subhajit Roychowdhury

Kanishka Biswas
title: The journey of tin chalcogenides towards high performance thermoelectrics and topological materials.
venue: Chemical communications
year: 2018

abstract: Dramatic enhancements in the figure of merit have been obtained in bulk thermoelectric materials by doping, band engineering, and nanostructuring. Especially, in p type thermoelectrics, high figure of merits near 2.0 have been reported in a few papers through the reduction in lattice thermal conductivity and the advancement in power factors. However, there exists no report on the n type systems showing high figure of merits because of their intrinsically low Seebeck coefficients. Here, we demonstrate that a nanostructured bulk n type thermoelectric material that was assembled by sintering spinodally decomposed lead chalcogenide nanoparticles having a composition of PbSe0.5Te0.5 reaches a high figure of merit of 1.85. The spinodally decomposed nanoparticles permit our thermoelectric material to have extremely low lattice thermal conductivity and a high power factor as a result of nanostructuring, electronic optimization, insertion of an impurity phase and phase change in local areas. We propose that this interesting concept would be one of the promising approaches that overcome limitation arising from the fact that most parameters in the figure of merit are closely correlated.
author_names: Min-Seok Kim

Woojin Lee

Ki Hyun Cho

Jae-Pyoung Ahn

Yun Mo Sung
title: Spinodally Decomposed PbSe PbTe Nanoparticles for High Performance Thermoelectrics: Enhanced Phonon Scattering and Unusual Transport Behavior.
venue: ACS nano
year: 2016

abstract: Abstract As an earth abundant material, PbS, has been paid extensive attention in the thermoelectric community. The high lattice thermal conductivity of PbS indicates there is room left to further improve thermoelectric performance of PbS. In this system we aimed to reduce the lattice thermal conductivity through nanostructuring grain sizes, which was processed by mechanical alloying followed by spark plasma sintering. We found that the lattice thermal conductivity can be reduced from ~1.5 W m 1 K 1 at 723 K for PbS ingot to as low as ~0.50 W m 1 K 1 for the PbS with nano scale grain sizes, as a result, a ZT value of 0.80 at 723 K was achieved for 1.0% PbCl 2 doped PbS with the second phases of Bi 2 S 3 (Sb 2 S 3 SrS, CaS) These results indicate that PbS is a robust alternative of PbTe and PbSe for medium temperature thermoelectric applications.
author_names: Cheng Chang

Yu Xiao

Xiao Zhang

Yan-Ling Pei

Fu Li

Shulan Ma

Bifei Yuan

Y Liu

Sheng-Kai Gong

Li-dong Zhao
title: High performance thermoelectrics from earth abundant materials: Enhanced figure of merit in PbS through nanostructuring grain size
year: 2016

abstract: Lead sulfide, a compound consisting of elements with high natural abundance, can be converted into an excellent thermoelectric material. We report extensive doping studies, which show that the power factor maximum for pure n type PbS can be raised substantially to ~12 mW cm( 1) K( 2) at >723 K using 1.0 mol PbCl(2) as the electron donor dopant. We also report that the lattice thermal conductivity of PbS can be greatly reduced by adding selected metal sulfide phases. The thermal conductivity at 723 K can be reduced by ~50% 52% 30% and 42% through introduction of up to 5.0 mol Bi(2)S(3) Sb(2)S(3) SrS, and CaS, respectively. These phases form as nanoscale precipitates in the PbS matrix, as confirmed by transmission electron microscopy (TEM) and the experimental results show that they cause huge phonon scattering. As a consequence of this nanostructuring, ZT values as high as 0.8 and 0.78 at 723 K can be obtained for nominal bulk PbS material. When processed with spark plasma sintering, PbS samples with 1.0 mol Bi(2)S(3) dispersion phase and doped with 1.0 mol PbCl(2) show even lower levels of lattice thermal conductivity and further enhanced ZT values of 1.1 at 923 K. The promising thermoelectric properties promote PbS as a robust alternative to PbTe and other thermoelectric materials.
author_names: Li-dong Zhao

Shih Han Lo

Jiaqing He

Hao Li

Kanishka Biswas

J G Androulakis

Chun I Wu

Timothy P Hogan

Duck Young Chung

Vinayak P Dravid

Mercouri G Kanatzidis
title: High performance thermoelectrics from earth abundant materials: enhanced figure of merit in PbS by second phase nanostructures.
venue: Journal of the American Chemical Society
year: 2011

abstract: High performance GeTe based thermoelectrics have been recently attracting growing research interest. Here, an overview is presented of the structural and electronic band characteristics of GeTe. Intrinsically, compared to low temperature rhombohedral GeTe, the high symmetry and high temperature cubic GeTe has a low energy offset between L and sigma points of the valence band, the reduced direct bandgap and phonon group velocity, and as a result, high thermoelectric performance. Moreover, their thermoelectric performance can be effectively enhanced through either carrier concentration optimization, band structure engineering (bandgap reduction, band degeneracy, and resonant state engineering) or restrained lattice thermal conductivity (phonon velocity reduction or phonon scattering) Consequently, the dimensionless figure of merit, ZT values, of GeTe based thermoelectric materials can be higher than 2. The mechanical and thermal stabilities of GeTe based thermoelectrics are highlighted, and it is found that they are suitable for practical thermoelectric applications except for their high cost. Finally, it is recognized that the performance of GeTe based materials can be further enhanced through synergistic effects. Additionally, proper material selection and module design can further boost the energy conversion efficiency of GeTe based thermoelectrics.
author_names: Wei-Di Liu

Deyong Wang

Qingfeng Liu

Wei Zhou

Zongping Shao

Zhi-Gang Chen
title: High Performance GeTe Based Thermoelectrics: from Materials to Devices
year: 2020