Effect of grain sizes and shapes on phonon thermal conductivity of bulk thermoelectric materials

AbstractNanocrystallization has been an important approach for reducing thermal conductivity in thermoelectric materials due to limits on phonon mean-free path imposed by the characteristic structural size. We report on thermal conductivity as low as 0.3 Wm−1K−1 of nanocrystalline silicon thin films prepared by plasma-enhanced chemical-vapor deposition as grain size is reduced to 2.8 nm by controlling hydrogen dilution of silane gas during growth. A multilayered film composed by alternating growth conditions, with layer thicknesses of 3.6 nm, is measured to have a thermal conductivity 30% and 15% lower than its two constituents. Our quantitative analysis attributes the strong reduction of thermal conductivity with decreasing grain size to the magnifying effect of porosity which occurs concomitantly due to increased mass density fluctuations. Our results demonstrate that ultrasmall grain sizes, multilayering, and porosity, all at a similar nanometer-size scale, may be a promising way to engineer thermoelectric materials.

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The origin of the lattice thermal conductivity enhancement at the ferroelectric phase transition in GeTe

npj Computational Materials ◽

10.1038/s41524-021-00523-7 ◽

2021 ◽

Vol 7 (1) ◽

Author(s):

Đorđe Dangić ◽

Olle Hellman ◽

Stephen Fahy ◽

Ivana Savić

Keyword(s):

Phase Transition ◽

Thermal Conductivity ◽

Phase Transitions ◽

Thermoelectric Materials ◽

Ferroelectric Phase Transition ◽

Lattice Thermal Conductivity ◽

Ferroelectric Phase ◽

Structural Phase ◽

High Symmetry ◽

Structural Phase Transitions

AbstractThe proximity to structural phase transitions in IV-VI thermoelectric materials is one of the main reasons for their large phonon anharmonicity and intrinsically low lattice thermal conductivity κ. However, the κ of GeTe increases at the ferroelectric phase transition near 700 K. Using first-principles calculations with the temperature dependent effective potential method, we show that this rise in κ is the consequence of negative thermal expansion in the rhombohedral phase and increase in the phonon lifetimes in the high-symmetry phase. Strong anharmonicity near the phase transition induces non-Lorentzian shapes of the phonon power spectra. To account for these effects, we implement a method of calculating κ based on the Green-Kubo approach and find that the Boltzmann transport equation underestimates κ near the phase transition. Our findings elucidate the influence of structural phase transitions on κ and provide guidance for design of better thermoelectric materials.

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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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Intrinsically Low Lattice Thermal Conductivity in Natural Superlattice (Bi2)m(Bi2Te3)n Thermoelectric Materials

Chemistry of Materials ◽

10.1021/acs.chemmater.0c03691 ◽

2021 ◽

Vol 33 (4) ◽

pp. 1140-1148

Author(s):

Hao Zhu ◽

Chenchen Zhao ◽

Pengfei Nan ◽

Xiao-ming Jiang ◽

Jiyin Zhao ◽

...

Keyword(s):

Thermal Conductivity ◽

Thermoelectric Materials ◽

Lattice Thermal Conductivity ◽

Natural Superlattice

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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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Lattice vibrational modes and phonon thermal conductivity of single-layer GaGeTe

Journal of Materiomics ◽

10.1016/j.jmat.2020.04.005 ◽

2020 ◽

Vol 6 (4) ◽

pp. 723-728

Author(s):

Jingyu Li ◽

Peng-Fei Liu ◽

Chi Zhang ◽

Xiaobo Shi ◽

Shujuan Jiang ◽

...

Keyword(s):

Thermal Conductivity ◽

Single Layer ◽

Vibrational Modes ◽

Phonon Thermal Conductivity

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Phonon thermal conductivity limited by electron scattering in amorphousZr70Cu30

Physical Review B ◽

10.1103/physrevb.27.3069 ◽

1983 ◽

Vol 27 (5) ◽

pp. 3069-3072 ◽

Cited By ~ 7

Author(s):

P. Esquinazi ◽

F. de la Cruz

Keyword(s):

Thermal Conductivity ◽

Electron Scattering ◽

Phonon Thermal Conductivity

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Metal phosphide CuP2 as a promising thermoelectric material: an insight from first-principles study

New Journal of Chemistry ◽

10.1039/d1nj03624f ◽

2021 ◽

Author(s):

Un-Gi Jong ◽

Chol-Hyok Ri ◽

Chol-Jin Pak ◽

Chol-Hyok Kim ◽

Stefaan Cottenier ◽

...

Keyword(s):

Thermal Conductivity ◽

Thermoelectric Material ◽

Thermoelectric Materials ◽

First Principles ◽

Lattice Thermal Conductivity ◽

Metal Phosphide ◽

First Principles Study ◽

Metal Phosphides ◽

Large Lattice

In the search for better thermoelectric materials, metal phosphides have not been considered to be viable candidates so far, due to their large lattice thermal conductivity. Here we study thermoelectric...

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