Phonon Scattering in Bi2Te3/Sb2Te3 Superlattice

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.

Phonon Scattering in Bi2Te3/Sb2Te3 Superlattice

2012 ◽  
Author(s):  
Yaguo Wang ◽  
Carl Liebig ◽  
Xianfan Xu ◽  
Rama Venkatasubramanian
Keyword(s):  
Heat Transport ◽  
Acoustic Phonon ◽  
Phonon Scattering ◽  
Scattering Mechanism ◽  
Acoustic Phonons ◽  
Time Resolved ◽  
Interface Scattering ◽  
Phonon Folding ◽  
Phonon Velocity ◽  
Time Resolved Measurements

Ultrafast time-resolved measurements were conducted to investigate scattering mechanism of coherent optical and acoustic phonons in Bi2Te3, Sb2Te3 and Bi2Te3/Sb2Te3 superlattice (SL) films. Strong phonon scatterings in the Bi2Te3/Sb2Te3 SLs are attributed to the interfaces of their hetero-structures. Moreover, decreases of acoustic phonon velocity are observed in SLs, coming from phonon folding and softening. Our results show that both the enhanced interface scattering and the reduced phonon velocity contribute to suppressing the heat transport in SLs.

scholarly journals Reduction of Lattice Thermal Conductivity in PbTe Induced by Artificially Generated Pores

2015 ◽  
Vol 2015 ◽  
pp. 1-6 ◽  
Author(s):  
Jae-Yeol Hwang ◽  
Eun Sung Kim ◽  
Syed Waqar Hasan ◽  
Soon-Mok Choi ◽  
Kyu Hyoung Lee ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Pore Structure ◽  
Transport Properties ◽  
Thermoelectric Materials ◽  
Thermal Transport ◽  
Lattice Thermal Conductivity ◽  
Phonon Scattering ◽  
Phonon Modes ◽  
Thermal Transport Properties

Highly dense pore structure was generated by simple sequential routes using NaCl and PVA as porogens in conventional PbTe thermoelectric materials, and the effect of pores on thermal transport properties was investigated. Compared with the pristine PbTe, the lattice thermal conductivity values of pore-generated PbTe polycrystalline bulks were significantly reduced due to the enhanced phonon scattering by mismatched phonon modes in the presence of pores (200 nm–2 μm) in the PbTe matrix. We obtained extremely low lattice thermal conductivity (~0.56 W m−1 K−1at 773 K) in pore-embedded PbTe bulk after sonication for the elimination of NaCl residue.

scholarly journals Hierarchically nanostructured thermoelectric materials: challenges and opportunities for improved power factors

2020 ◽  
Vol 93 (11) ◽  
Author(s):  
Neophytos Neophytou ◽  
Vassilios Vargiamidis ◽  
Samuel Foster ◽  
Patrizio Graziosi ◽  
Laura de Sousa Oliveira ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Power Factor ◽  
High Power ◽  
Thermoelectric Materials ◽  
Phonon Scattering ◽  
Electronic Device ◽  
Macro Scale ◽  
Challenges And Opportunities ◽  
Recent Developments ◽  
New Generation

Abstract The field of thermoelectric materials has undergone a revolutionary transformation over the last couple of decades as a result of the ability to nanostructure and synthesize myriads of materials and their alloys. The ZT figure of merit, which quantifies the performance of a thermoelectric material has more than doubled after decades of inactivity, reaching values larger than two, consistently across materials and temperatures. Central to this ZT improvement is the drastic reduction in the material thermal conductivity due to the scattering of phonons on the numerous interfaces, boundaries, dislocations, point defects, phases, etc., which are purposely included. In these new generation of nanostructured materials, phonon scattering centers of different sizes and geometrical configurations (atomic, nano- and macro-scale) are formed, which are able to scatter phonons of mean-free-paths across the spectrum. Beyond thermal conductivity reductions, ideas are beginning to emerge on how to use similar hierarchical nanostructuring to achieve power factor improvements. Ways that relax the adverse interdependence of the electrical conductivity and Seebeck coefficient are targeted, which allows power factor improvements. For this, elegant designs are required, that utilize for instance non-uniformities in the underlying nanostructured geometry, non-uniformities in the dopant distribution, or potential barriers that form at boundaries between materials. A few recent reports, both theoretical and experimental, indicate that extremely high power factor values can be achieved, even for the same geometries that also provide ultra-low thermal conductivities. Despite the experimental complications that can arise in having the required control in nanostructure realization, in this colloquium, we aim to demonstrate, mostly theoretically, that it is a very promising path worth exploring. We review the most promising recent developments for nanostructures that target power factor improvements and present a series of design ‘ingredients’ necessary to reach high power factors. Finally, we emphasize the importance of theory and transport simulations for materialoptimization, and elaborate on the insight one can obtain from computational tools routinely used in the electronic device communities. Graphical abstract

scholarly journals Employing Interfaces with Metavalently Bonded Materials for Phonon Scattering and Control of the Thermal Conductivity in TAGS‐ x Thermoelectric Materials

2020 ◽  
Vol 30 (17) ◽  
pp. 1910039 ◽  
Author(s):  
Cynthia Rodenkirchen ◽  
Matteo Cagnoni ◽  
Stefan Jakobs ◽  
Yudong Cheng ◽  
Jens Keutgen ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Thermoelectric Materials ◽  
Phonon Scattering ◽  
Bonded Materials ◽  
And Control

Phonon Scattering and Thermal Conductivity in p-Type Nanostructured PbTe-BaTe Bulk Thermoelectric Materials

2012 ◽  
Vol 22 (24) ◽  
pp. 5175-5184 ◽  
Author(s):  
Shih-Han Lo ◽  
Jiaqing He ◽  
Kanishka Biswas ◽  
Mercouri G. Kanatzidis ◽  
Vinayak P. Dravid
Keyword(s):  
Thermal Conductivity ◽  
Thermoelectric Materials ◽  
Phonon Scattering ◽  
P Type

THERMOELECTRICITY OF Ca2.9Ce0.1Co4O9+δ BASED NANOCOMPOSITES WITH Cu2O NANOINCLUSION

2013 ◽  
Vol 27 (22) ◽  
pp. 1350108
Author(s):  
FANG JU LI
Keyword(s):  
Thermal Conductivity ◽  
Electrical Resistivity ◽  
Energy Harvesting ◽  
Thermoelectric Properties ◽  
Thermoelectric Materials ◽  
Phonon Scattering ◽  
Temperature Dependent ◽  
Resistivity Measurements ◽  
Carrier Scattering ◽  
Scattering Centers

Ca 2.9 Ce 0.1 Co 4 O 9+δ/x wt% Cu 2 O nanocomposites have been studied as the thermoelectric materials for energy harvesting purpose. We evaluate the thermoelectric properties of the composites through temperature dependent thermopower, thermal conductivity and resistivity measurements. It is found that the introduction of Cu 2 O nanoparticles serves as phonon scattering centers, which reduces the thermal conductivity. The nanoinclusions contribute to a remarkable increase in electrical resistivity due to enhanced carrier scattering. As a result, Cu 2 O nanoinclusions do not succeed in improving ZT of Ca 2.9 Ce 0.1 Co 4 O 9+δ material.

scholarly journals Giant isotope effect on phonon dispersion and thermal conductivity in methylammonium lead iodide

2020 ◽  
Vol 6 (31) ◽  
pp. eaaz1842
Author(s):  
M. E. Manley ◽  
K. Hong ◽  
P. Yin ◽  
S. Chi ◽  
Y. Cai ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
High Performance ◽  
Phonon Scattering ◽  
Light Emission ◽  
Phonon Dispersion ◽  
Acoustic Phonons ◽  
Lead Iodide ◽  
Phonon Bottleneck ◽  
Optic Phonon ◽  
Methylammonium Lead Iodide

Lead halide perovskites are strong candidates for high-performance low-cost photovoltaics, light emission, and detection applications. A hot-phonon bottleneck effect significantly extends the cooling time of hot charge carriers, which thermalize through carrier–optic phonon scattering, followed by optic phonon decay to acoustic phonons and finally thermal conduction. To understand these processes, we adjust the lattice dynamics independently of electronics by changing isotopes. We show that doubling the mass of hydrogen in methylammonium lead iodide by replacing protons with deuterons causes a large 20 to 50% softening of the longitudinal acoustic phonons near zone boundaries, reduces thermal conductivity by ~50%, and slows carrier relaxation kinetics. Phonon softening is attributed to anticrossing with the slowed libration modes of the deuterated molecules and the reduced thermal conductivity to lowered phonon velocities. Our results reveal how tuning the organic molecule dynamics enables control of phonons important to thermal conductivity and the hot-phonon bottleneck.

Thermoelectric Properties of Hot-Pressed Ultra-Fine Particulate Sige Powder Alloys with Inert Additions

1991 ◽  
Vol 234 ◽  
Author(s):  
John S. Beaty ◽  
Jonathan L Rolfe ◽  
Jan W. Vandersande
Keyword(s):  
Thermal Conductivity ◽  
Silicon Nitride ◽  
Thermoelectric Materials ◽  
Phonon Scattering ◽  
Fine Powder ◽  
Fine Particulates ◽  
High Temperature Heat Treatment ◽  
Scattering Centers ◽  
Efficiency Theory ◽  
P Type

ABSTRACTThe objective of the work reported here is to reduce the thermal conductivity of thermoelectric materials in order to improve their figureof- merit and conversion efficiency. Theory predicts that the addition of ultra-fine, inert, phonon-scattering centers to thermoelectric materials will reduce their thermal conductivity [1]. To investigate this prediction, ultra-fine particulates (20Å to 120Å) of silicon nitride have been added to boron doped, p-type, 80/20 SiGe. All of the SiGe samples produced from ultra-fine powder have lower thermal conductivities, than that for standard SiGe, but high temperature heat treatment increases the thermal conductivity back to the value for standard SiGe. However, the SiGe samples with silicon nitride, inert, phonon-scattering centers, retained the lower thermal conductivity after several heat treatments. A reduction of approximately 25% in thermal conductivity has been achieved in these samples.

Effect of fullerene addition on thermoelectric properties ofn-type skutterudite compound

2007 ◽  
Vol 22 (1) ◽  
pp. 249-253 ◽  
Author(s):  
Takashi Itoh ◽  
Kenta Ishikawa ◽  
Akira Okada
Keyword(s):  
Thermal Conductivity ◽  
Power Generation ◽  
Thermoelectric Properties ◽  
Thermoelectric Materials ◽  
Phonon Scattering ◽  
Grinding Method ◽  
Milling Method ◽  
Compound Matrix ◽  
Skutterudite Compound ◽  
Dispersion Of Nanoparticles

Thermoelectric power generation is a promising method for harnessing waste thermal energy, especially in the temperature range between 500 and 800 K. It is necessary to improve the performance of thermoelectric materials for the realization of the power generation. Dispersion of nanoparticles such as fullerenes is expected to induce phonon scattering that decreases thermal conductivity of materials, and application to thermoelectric materials may lead to improved properties. In the present study, then-type Co0.92Ni0.08Sb2.96Te0.04thermoelectric compound was synthesized, and the thermoelectric properties were evaluated. Furthermore, the fullerene particles were sufficiently mixed with the thermoelectric compound powder by the mechanical grinding method, and influences of the fullerene additions to the compound were investigated. The dispersion of fullerene particles in then-type Co0.92Ni0.08Sb2.96Te0.04compound was conducted through the planetary ball milling method to disentangle agglomerates of the fullerene and to disperse the particles in the thermoelectric compound matrix. The thermal conductivity decreased with an increase in fullerene content, and the maximum in dimensionless figure of meritZTwas 0.62 at 800 K for 1 mass% fullerene addition. This was 28% higher than that of fullerene-free sample.

Thermal Transport in Rough Silicon Nanowires for Thermoelectric Applications

2009 ◽  
Vol 1166 ◽  
Author(s):  
Sanjiv Sinha ◽  
Bair Budhaev ◽  
Arun Majumdar
Keyword(s):  
Thermal Conductivity ◽  
Silicon Nanowires ◽  
Thermoelectric Materials ◽  
Thermal Transport ◽  
Phonon Scattering ◽  
Phonon Localization ◽  
Material Concept ◽  
Electron Crystal ◽  
The Ideal ◽  
Nanostructured Thermoelectric Materials

AbstractThe coefficient of merit, ZT of nanostructured thermoelectric materials increases with reduction in thermal conductivity through phonon scattering. The ideal thermoelectric is considered to be an electron crystal and a phonon glass. This paper explores such a material concept by developing a theory for phonon localization in rough nanowires with crystalline cores. Results based on this theory suggest that the reported hundredfold decrease in thermal conductivity of rough silicon nanowires arises due to multiply scattered and localized phonons. Phonon localization presents a new direction to further enhance ZT through nanostructuring.

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