Crystal Lattice Controlled SiGe Thermoelectric Materials with High Figure of Merit

ABSTRACTDirect energy conversion between thermal and electrical energy, based on thermoelectric (TE) effect, has the potential to recover waste heat and convert it to provide clean electric power. The energy conversion efficiency is related to the thermoelectric figure of merit ZT expressed as ZT=S2σT/κ, T is temperature, S is the Seebeck coefficient, σ is conductance and κ is thermal conductivity. For a lower thermal conductivity κ and high power factor (S2σ), our current strategy is the development of rhombohedrally strained single crystalline SiGe materials that are highly [111]-oriented twinned. The development of a SiGe “twin lattice structure (TLS)” plays a key role in phonon scattering. The TLS increases the electrical conductivity and decreases thermal conductivity due to phonon scattering at stacking faults generated from the 60° rotated primary twin structure. To develop high performance materials, the substrate temperature, chamber working pressure, and DC sputtering power are controlled for the aligned growth production of SiGe layer and TLS on a c-plane sapphire. Additionally, a new elevated temperature thermoelectric characterization system, that measures the thermal diffusivity and Seebeck effect nondestructively, was developed. The material properties were characterized at various temperatures and optimized process conditions were experimentally determined. The present paper encompasses the technical discussions toward the development of thermoelectric materials and the measurement techniques.

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Thermoelectric Transport in Silicon Germanium Nanocomposite

Volume 13: Nano-Manufacturing Technology; and Micro and Nano Systems, Parts A and B ◽

10.1115/imece2008-67436 ◽

2008 ◽

Author(s):

Hohyun Lee ◽

Daryoosh Vashaee ◽

Xiaowei Wang ◽

Giri Joshi ◽

Gaohua Zhu ◽

...

Keyword(s):

Thermal Conductivity ◽

Energy Conversion ◽

Silicon Germanium ◽

Figure Of Merit ◽

Waste Heat ◽

Electrical Energy ◽

Energy Conversion Efficiency ◽

Thermoelectric Effects ◽

Thermoelectric Transport ◽

Potential Applications

Direct energy conversion between heat and electrical energy based on thermoelectric effects is attractive for potential applications in waste heat recovery and environmentally-friendly refrigeration. The energy conversion efficiency depends on the dimensionless figure of merit of thermoelectric materials, ZT, which is proportional to the electrical conductivity, the square of the Seebeck coefficient, and the inverse of the thermal conductivity. Currently, the low ZT values of available materials restrict the applications of this technology. However, significant enhancements in ZT were recently reported in nanostructured materials such as superlattices mainly due to their low thermal conductivities. According to recent studies, the reduced thermal conductivity of nanostructures is attributed to the large number of interfaces at which phonons are scattered. Based on this idea, nanocomposites are expected to have a lower thermal conductivity than their bulk counterparts with low fabrication cost just by mixing nano sized particles. In this work, we will discuss mechanisms of thermoelectric transport via modeling and provide experimental evidence on the enhancement of thermoelectric figure of merit in SiGe-based nanocomposites.

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Structural Modularization of Cu2Te Leading to High Thermoelectric Performance near the Mott-Ioffe-Regel Limit

10.21203/rs.3.rs-699516/v1 ◽

2021 ◽

Author(s):

Kunpeng Zhao ◽

Chenxi Zhu ◽

Min Zhu ◽

Hongyi Chen ◽

Jindan Lei ◽

...

Keyword(s):

Thermal Conductivity ◽

Energy Conversion ◽

Thermoelectric Materials ◽

High Performance ◽

Figure Of Merit ◽

Rational Design ◽

Absolute Temperature ◽

Band Edge ◽

Total Thermal Conductivity ◽

Te Material

Abstract To date, thermoelectric materials research stays focused on optimizing the material’s band edge details and disfavors low mobility. Here, we shifts the paradigm from the band edge to the mobility edge, exploring high thermoelectricity near the border of band conduction and hopping. Through co-alloying iodine and sulfur, we modularize the plain crystal structure of liquid-like thermoelectric material Cu2Te with mosaic nanodomains and the highly size mismatched S/Te sublattice that chemically quenches the Cu sublattice and drives the electronic states from itinerant to localized. A state-of-the-art figure of merit of 1.4 is obtained at 850 K for Cu2(S0.4I0.1Te0.5); and remarkably, it is achieved near the Mott-Ioffe-Regel limit unlike mainstream thermoelectric materials that are band conductors. Broadly, pairing structural modularization with the high performance near the Mott-Ioffe-Regel limit paves an important new path towards the rational design of high-performance thermoelectric materials. Thermoelectric (TE) material-based energy conversion technology has attracted increasing global attention in virtue of the technical merits such as no moving parts, no greenhouse emission, noiseless, friendliness for miniaturization, and reliability.1–4 Based on the Seebeck and Peltier effects, thermoelectricity enables a direct energy conversion between temperature difference and electricity.5, 6 The performance of a TE material is primarily gauged by the material’s figure of merit, zT = S2T/ρκ, where S is the Seebeck coefficient, T is the absolute temperature, ρ is the electrical resistivity, and κ is the total thermal conductivity (consisting of the lattice thermal conductivity κL and the electronic thermal conductivity κE).

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High-entropy-stabilized chalcogenides with high thermoelectric performance

Science ◽

10.1126/science.abe1292 ◽

2021 ◽

Vol 371 (6531) ◽

pp. 830-834 ◽

Cited By ~ 6

Author(s):

Binbin Jiang ◽

Yong Yu ◽

Juan Cui ◽

Xixi Liu ◽

Lin Xie ◽

...

Keyword(s):

Thermoelectric Materials ◽

Performance Optimization ◽

Figure Of Merit ◽

Phonon Scattering ◽

Waste Heat ◽

Configurational Entropy ◽

Thermoelectric Performance ◽

Structural Stabilization ◽

High Entropy ◽

Thermoelectric Conversion

Thermoelectric technology generates electricity from waste heat, but one bottleneck for wider use is the performance of thermoelectric materials. Manipulating the configurational entropy of a material by introducing different atomic species can tune phase composition and extend the performance optimization space. We enhanced the figure of merit (zT) value to 1.8 at 900 kelvin in an n-type PbSe-based high-entropy material formed by entropy-driven structural stabilization. The largely distorted lattices in this high-entropy system caused unusual shear strains, which provided strong phonon scattering to largely lower lattice thermal conductivity. The thermoelectric conversion efficiency was 12.3% at temperature difference ΔT = 507 kelvin, for the fabricated segmented module based on this n-type high-entropy material. Our demonstration provides a paradigm to improve thermoelectric performance for high-entropy thermoelectric materials through entropy engineering.

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SnSe, the rising star thermoelectric material: a new paradigm in atomic blocks, building intriguing physical properties

Materials Horizons ◽

10.1039/d1mh00091h ◽

2021 ◽

Author(s):

Lin Xie ◽

Dongsheng He ◽

Jiaqing He

Keyword(s):

Physical Properties ◽

Energy Conversion ◽

Thermoelectric Material ◽

Thermoelectric Materials ◽

Waste Heat ◽

New Paradigm ◽

Direct Energy Conversion ◽

Structures And Properties ◽

Direct Energy

Thermoelectric materials, which enable direct energy conversion between waste heat and electricity, are witnessing exciting developments due to innovative breakthroughs both in materials and the synergistic optimization of structures and properties.

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Investigation of Thermoelectric Materials: Substitution effect of Bi on the Ag1-xPb18MTe20 (M = Sb, Bi) (x = 0, 0.14, 0.3)

MRS Proceedings ◽

10.1557/proc-1044-u03-14 ◽

2007 ◽

Vol 1044 ◽

Author(s):

Mi-kyung Han ◽

Huijun Kong ◽

Ctirad Uher ◽

Mercouri G Kanatzidis

Keyword(s):

Thermal Conductivity ◽

Electrical Conductivity ◽

Seebeck Coefficient ◽

Thermoelectric Materials ◽

Figure Of Merit ◽

Lattice Thermal Conductivity ◽

Substitution Effect ◽

Dimensionless Figure Of Merit ◽

The Matrix ◽

Mass Fluctuation

AbstractWe performed comparative investigations of the Ag1-xPb18MTe20 (M = Bi, Sb) (x = 0, 0.14, 0.3) system to better understand the roles of Sb and Bi on the thermoelectric properties. In both systems, the electrical conductivity nearly keeps the same values, while the Seebeck coefficient decreases dramatically in going from Sb to Bi. Compared to the lattice thermal conductivity of PbTe, that of AgPb18BiTe20 is substantially reduced. The lattice thermal conductivity of the Bi analog, however, is higher than that of AgPb18SbTe20 and this is attributed largely to the decrease in the degree of mass fluctuation between the nanostructures and the matrix (for the Bi analog). As a result the dimensionless figure of merit ZT of Ag1-xPb18MTe20 (M = Bi) is found to be smaller than that of Ag1-xPb18MTe20 (M = Sb).

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Thermoelectric Materials for Textile Applications

Molecules ◽

10.3390/molecules26113154 ◽

2021 ◽

Vol 26 (11) ◽

pp. 3154

Author(s):

Kony Chatterjee ◽

Tushar K. Ghosh

Keyword(s):

Thermal Conductivity ◽

Carbon Nanotubes ◽

Seebeck Coefficient ◽

Thermoelectric Materials ◽

Figure Of Merit ◽

Inorganic Materials ◽

Peltier Effect ◽

Electronic Textiles ◽

Heating And Cooling ◽

Recent Attention

Since prehistoric times, textiles have served an important role–providing necessary protection and comfort. Recently, the rise of electronic textiles (e-textiles) as part of the larger efforts to develop smart textiles, has paved the way for enhancing textile functionalities including sensing, energy harvesting, and active heating and cooling. Recent attention has focused on the integration of thermoelectric (TE) functionalities into textiles—making fabrics capable of either converting body heating into electricity (Seebeck effect) or conversely using electricity to provide next-to-skin heating/cooling (Peltier effect). Various TE materials have been explored, classified broadly into (i) inorganic, (ii) organic, and (iii) hybrid organic-inorganic. TE figure-of-merit (ZT) is commonly used to correlate Seebeck coefficient, electrical and thermal conductivity. For textiles, it is important to think of appropriate materials not just in terms of ZT, but also whether they are flexible, conformable, and easily processable. Commercial TEs usually compromise rigid, sometimes toxic, inorganic materials such as bismuth and lead. For textiles, organic and hybrid TE materials are more appropriate. Carbon-based TE materials have been especially attractive since graphene and carbon nanotubes have excellent transport properties with easy modifications to create TE materials with high ZT and textile compatibility. This review focuses on flexible TE materials and their integration into textiles.

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Influence of multi-sintering on the thermoelectric properties of Bi2Sr2Co2Oy ceramics

Modern Physics Letters B ◽

10.1142/s0217984920500190 ◽

2019 ◽

Vol 34 (02) ◽

pp. 2050019 ◽

Cited By ~ 2

Author(s):

Y. Zhang ◽

M. M. Fan ◽

C. C. Ruan ◽

Y. W. Zhang ◽

X.-J. Li ◽

...

Keyword(s):

Thermal Conductivity ◽

Thermoelectric Properties ◽

Figure Of Merit ◽

Phonon Scattering ◽

Sintered Sample ◽

Thermoelectric Figure Of Merit ◽

Thermoelectric Figure ◽

The Third ◽

Ceramic Samples ◽

Optimum Formula

[Formula: see text] ceramic samples have a structure similar to phonon glass electronic crystals, and their thermoelectric properties can be effectively adjusted through repeated grinding and sintering. The results show that multi-sintering can make their grain refined and increase their grain boundary, which will effectively increase density and phonon scattering. Finally, multi-sintering can reduce the resistivity and thermal conductivity, thus obviously improve thermoelectric figure of merit [Formula: see text] of [Formula: see text]. The optimum [Formula: see text] value of 0.26 is achieved at 923 K by the third sintered sample.

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Polycrystalline SnSe with a thermoelectric figure of merit greater than the single crystal

Nature Materials ◽

10.1038/s41563-021-01064-6 ◽

2021 ◽

Cited By ~ 1

Author(s):

Chongjian Zhou ◽

Yong Kyu Lee ◽

Yuan Yu ◽

Sejin Byun ◽

Zhong-Zhen Luo ◽

...

Keyword(s):

Thermal Conductivity ◽

Single Crystal ◽

High Performance ◽

Figure Of Merit ◽

Waste Heat ◽

Electric Energy ◽

Cost Effective ◽

Tin Selenide ◽

Tin Oxides ◽

Thermally Conductive

AbstractThermoelectric materials generate electric energy from waste heat, with conversion efficiency governed by the dimensionless figure of merit, ZT. Single-crystal tin selenide (SnSe) was discovered to exhibit a high ZT of roughly 2.2–2.6 at 913 K, but more practical and deployable polycrystal versions of the same compound suffer from much poorer overall ZT, thereby thwarting prospects for cost-effective lead-free thermoelectrics. The poor polycrystal bulk performance is attributed to traces of tin oxides covering the surface of SnSe powders, which increases thermal conductivity, reduces electrical conductivity and thereby reduces ZT. Here, we report that hole-doped SnSe polycrystalline samples with reagents carefully purified and tin oxides removed exhibit an ZT of roughly 3.1 at 783 K. Its lattice thermal conductivity is ultralow at roughly 0.07 W m–1 K–1 at 783 K, lower than the single crystals. The path to ultrahigh thermoelectric performance in polycrystalline samples is the proper removal of the deleterious thermally conductive oxides from the surface of SnSe grains. These results could open an era of high-performance practical thermoelectrics from this high-performance material.

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Phonon Scattering in Bi2Te3/Sb2Te3 Superlattice

ASME/JSME 2011 8th Thermal Engineering Joint Conference ◽

10.1115/ajtec2011-44012 ◽

2011 ◽

Author(s):

Yaguo Wang ◽

Xianfan Xu ◽

Rama Venkatasubramanian

Keyword(s):

Thermal Conductivity ◽

Thermoelectric Materials ◽

Phonon Scattering ◽

Quantum Confinement Effect ◽

Theoretical Models ◽

Heat Transfer Process ◽

Acoustic Phonons ◽

Time Resolved ◽

Hetero Structure ◽

Phonon Velocity

Thermoelectric materials are characterized with the figure of merit, ZT = S2σT/κ, where T is the temperature, S the Seebeck coefficient, σ the electrical conductivity and κ the thermal conductivity. Many researches have been focused on reducing lattice thermal conductivity through increasing phonon scattering at interfaces. Thin-film superlattices are one of the promising candidates for high ZT thermoelectric materials. Several theoretical models have been used to explain the large ZT in superlattice. One comes from the extra scattering channels at interfaces introduced by the hetero-structure. Another is a result of quantum confinement effect which reduces the phonon group velocity propagating perpendicularly through the superlattice layers through flattening the dispersion curve of acoustic phonons. In this work, ultrafast time-resolved measurements were conducted on Bi2Te3, Sb2Te3 and Bi2Te3/Sb2Te3 superlattice (SL) films to detect coherent acoustic phonons in these materials. Scattering of these phonons is revealed in the Bi2Te3/Sb2Te3 SLs, which comes from the interfaces of the hetero-structure in SL. Also, a decrease of acoustic phonon velocity resulted from folding and flattening of phonons branches is observed. Results show that both interface scattering and the reduced phonon velocity contribute to suppressing the heat transfer process.

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