Symposium Organizers
Terry M. Tritt Clemson University
George S. Nolas University of South Florida
Yuri Grin Max-Planck Institute for Chemical Physics of Solids
Jeff Sharp Marlow Industries, Inc.
LL1: Thermoelectrics: General
Session Chairs
Monday PM, November 29, 2010
Commonwealth (Sheraton)
10:30 AM - **LL1.1
Structure and Aims of Recent Thermoelectric Programs in Germany.
Harald Boettner 1
1 TES, Fraunhofer IPM, Freiburg Germany
Show AbstractIt is obvious that worldwide activities in thermoelectrics do increase significantly. Thus J. Goldsmid (ICT 2010) expected an upcoming golden decade for thermoelectrics.In contrast to the consequent support for thermoelectrics in USA starting with the implementation of RTG's as power source for space research the activities in thermoelectrics in Germany were on a rather limited level.In recent years the situation did change completely driven by topics energy efficiency, waste heat recovery, miniaturized devices, stand alone sensor systems, and in particular nanoscale material science for thermoelectrics. To strengthen the basic physical and chemical knowledge on different nanoscale thermoelectric approaches the German DFG "German research society" is funding since middle 2009 a priority program "Nanoscale thermoelectrics". In addition, based on a proposal named HoTT (High Temperature Thermoelectrics) the BMBF (Federal Ministry of Education and Research) launched a program at the beginning of 2010 called "Thermopower", which acts as an umbrella for 11 applied oriented projects.Both programs cover different aspects from basic research, material science and industrial application.In this survey structure and content of the programs will be reported including interdependencies. Additional information on current EU-FP7 funded projects will be given.
11:00 AM - **LL1.2
The Department of Energy/National Science Foundation Partnership on Thermoelectric Devices for Vehicle Applications.
John Fairbanks 1 , C. Thomas Avedisian 2 , Theodore Bergman 3
1 Vehicle Technologies Program, US Department of Energy, Washington, District of Columbia, United States, 2 Sibley School of Mechanical and Aerospace Engineering, Cornell University, Ithaca, New York, United States, 3 Department of Mechanical Engineering, University of Connecticut, Storrs, Connecticut, United States
Show AbstractThe Department of Energy's (DOE's) Vehicle Technologies Program (VTP) has a long history of supporting research and development to utilize thermoelectric generator (TEG) technology for waste heat recovery in automotive systems. Such devices might be installed within the exhaust system of a vehicle to convert the energy within the hot combustion products into high-grade electrical power. In this way thermoelectric devices could allow for smaller alternators and reduced engine load that would increase fuel economy.The long term goal is to improve fuel economy by 10 percent. The emphasis on DOE’s efforts to this end have been to fund development and manufacturing by industry-led teams through a number of Cooperative Agreements (e.g., with BSST, Ford, Visteon and BMW; GM, GE, Delphi, and Marlow; Michigan State University, NASA, JPL, and Cummins). Some of these efforts have led to production prototype TEGs for heavy duty diesel trucks and commercial transportation vehicles (i.e., the Ford Fusion and the BMW X-6 and Series 5 vehicles). The 1st generation TEG's developed by these teams are anticipated to provide a nominal 5 percent improvement of highway fuel economy, which would be achieved by reducing the alternator load by a third. The complete elimination of the alternator by converting waste heat to electricity through thermoelectric means calls for a more integrated approach that rests upon a highly-linked set of interdisciplinary challenges that involve not only materials development but bridging across system levels through interfaces, heat sink design and convective and radiative processes. To this end, the DOE and the National Science Foundation (NSF) have partnered to develop a jointly funded program at a level of $3M/year with equal shares from DOE and NSF. From 6 to 9 teams would be selected with university PIs as the lead. This partnership is intended to exploit the complementary missions of NSF and DOE to promote new discovery through research and development, and deployment and commercialization. The deliverables will include the critical understanding and technology improvements that are required to make viable the efficient conversion of waste heat in automotive exhaust systems to electricity. The intent is to ensure focus on commercially viable materials. The NSF procurement cycle began with a Letter of Intent (LOI) that led to selection of 6 to 9 proposals for funding. A brief summary of the selected projects will be presented. Also, the status of development of the 1st generation TEG's for Ford, BMW and GM will be presented.
11:30 AM - LL1.3
Progress on Thermoelectric Generator Development for Automotive Exhaust Gas Waste Heat Recovery.
Gregory Meisner 1
1 Chemical Sciences & Material Systems Lab, GM Global R&D, Warren, Michigan, United States
Show AbstractGeneral Motors Global R&D has an ongoing research program to develop advanced thermoelectric (TE) technology for automotive waste heat recovery, and we have made significant progress on constructing a working prototype automotive TE generator (TEG). The modeling for the design of our prototype TEG was based on exhaust gas characteristics of a GM production vehicle using the Federal Test Procedure for urban and highway drive cycles. The design was optimized by minimizing the cost per watt of electrical power generated averaged over the drive cycle using the properties of known state of the art TE materials and modules, estimates of the various material and fabrication costs, and the performance of the heat exchanger. The fabrication and assembly of the prototype has been completed, and it has been installed on a test vehicle, which included completion of all the exhaust system modifications, incorporation of a bypass valve system, and installation of the required controls and integration electronics. Data from the TEG sensors and TE module outputs have now provided important preliminary data for the operation of the mechanical, thermal, and electrical systems of the TEG in combination with the various vehicle systems; including exhaust bypass valve controls, thermocouples, gas and coolant flow and pressure sensors, and the TE output voltage and electrical power. Our recent results on this functioning TEG will be presented. Essential to the long term success of TEGs for production vehicles is continued new TE materials research and the development of those materials into robust and high performance TE modules. Our work in this area includes Skutterudite-type materials systems, and some of those results will also be presented. GM gratefully acknowledges funding from the U.S. Department of Energy in support of this work.
11:45 AM - LL1.4
Bottom-up Strategy Towards Thermoelectric Materials With Nano-scale Domains.
Anuja Datta 1 , J. Paul 1 , A. Popescu 1 , L. Woods 1 , G. Nolas 1
1 Department of Physics, University of South Florida, Tampa, Florida, United States
Show AbstractA two-step bottom-up strategy was implemented in preparing bulk thermoelectric nanocomposites. The approach involved composition and size controlled syntheses of thermoelectric materials as nanocrystals by facile solution based processes followed by densification into bulk pellets by Spark Plasma Sintering (SPS). Synthesis approaches were selected based on the effectiveness of yielding organics free nanocrystals in large quantity. Densification of nanocrystals by SPS contributed to the uniform distribution of nano-scale domains in the bulk matrix material that also preserved the nanostructures. Doping of the nanocrystals allowed for modifications of the bulk carrier concentrations. Electronic and thermal transport properties of the nanocomposites were evaluated and indicated enhancement in the thermoelectric properties as compared to that of bulk materials. The bottom-up strategy was investigated in the context of research into cost-effective, scalable, and reproducible materials preparation approaches towards improving the thermoelectric properties of existing materials.*This work is supported by the U.S. Army Medical Research and Materiel Command under Grant No. W81XWH-07-1-0708 and the National Science Foundation under Grant Nos. CBET-0932526 and CMMI-0927637.
12:00 PM - **LL1.5
Rapid Solidification Methods for Fabrication of Novel Thermoelectric Materials.
Xinfeng Tang 1 , Wenjie Xie 1 2 , Han Li 1 , Yonggao Yan 1 , Qingjie Zhang 1 , Ctirad Uher 3 , Terry Tritt 2
1 State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan, Hubei, China, 2 Department of Physics and Astronomy, Clemson University, Clemson, South Carolina, United States, 3 Department of Physics, University of Michigan, Ann Arbor, Michigan, United States
Show AbstractThe development of novel preparation technique about high-performance thermoelectric materials with nanostructure is of great significance to the commercial applications. In this research, we developed a new synthesis route that is melt spinning combined with spark plasma sintering technique (MS-SPS) to rapidly prepare nanostructured thermoelectric materials. Using this synthesis route, we have prepared p-type Bi-Sb-Te bulk materials with some special nanostructures (such as amorphous structure, fine nano-crystalline, quasi-coherent structure and so on) by MS-SPS. This system show very low thermal conductivity while they possess good electrical transport properties, and therefore ZTmax reaches 1.56 at 300 K. The nanostructured Bi-Sb-Te bulk materials show a very high compressive strength which is double of zone-melting samples. Moreover, we also prepared nanostructured n-type Yb0.3Co4Sb12+y bulk materials and InxCeyCo4Sb12 compounds with evenly dispersed nano-InSb (10 ~ 80 nm) second phase on the boundaries. More importantly, compared with traditional method, the preparation time of filled Skutterudite by using MS-SPS can be notably reduced from 10 days to less than 40 hours. The ZTmax reaches 1.45 at 800 K for n-type In0.15Ce0.15Co4Sb12 compound prepared by MS-SPS technique.
12:30 PM - LL1.6
Quasi-ballistic Heat Transfer from Metal Nanostructures on Sapphire.
Austin Minnich 1 , Gang Chen 1
1 Mechanical Engineering, MIT, Cambridge, Massachusetts, United States
Show AbstractQuasi-ballistic phonon transport, where heat transfer is not diffusive and does not obey Fourier's law, has been theoretically predicted to occur when length or time scales become comparable to the phonon mean free path or relaxation time. Understanding this regime of heat transport is of fundamental interest, as the manner in which the heat transport deviates from Fourier's law reveals important information about the distribution of phonon mean free paths. This distribution is still not known with certainty even in crystalline silicon. Transient thermoreflectance is a common experimental technique to study heat transfer with sub-picosecond resolution using femtosecond laser pulses; however, the minimum size of the heated region is fundamentally restricted to the diffraction-limited spot size. In this work, we fabricate arrays of aluminum dots on sapphire with diameters as small as 50 nm to act as light absorbers rather than the usual continuous metal film. In this way, we obtain a spatial resolution far below the diffraction limit and comparable to the phonon mean free paths in sapphire. We show that ballistic phonons play a critical role in the heat transfer at these length and time scales. We expect this technique will prove useful to analyzing phonon mean free paths in bulk and nanostructured thermoelectric materials.
12:45 PM - LL1.7
High-performance Thermoelectric Cooling Modules Based on Advanced Bulk Nanostructured Materials.
Chris Caylor 1 , Jonathan D'Angelo 1 , Lon Bell 2 , Zhifeng Ren 3 , C. Chen 4
1 , GMZ Energy, Waltham, Massachusetts, United States, 2 , BSST, Irwindale, California, United States, 3 , Boston College, Chesnut Hill, Massachusetts, United States, 4 , Teledyne, Thousand Oaks, California, United States
Show AbstractThe development of nanostructured bulk bismuth telluride alloys, which exhibit high thermoelectric performance compared to state-of-the-art materials, will enable the fabrication of high heat flux cooling devices capable of operating with a coefficient of performance greater than two. GMZ Energy, Boston College, BSST and Teledyne are working to bring these devices to fruition based on increased materials performance, minimizing device parasitics (such as electrical and thermal contact resistances) and utilizing micro-machining device fabrication techniques. The status of these important aspects will be reported.
LL2: Skutterudites/Clathrates and Skutterudites
Session Chairs
George Nolas
James Salvador
Monday PM, November 29, 2010
Commonwealth (Sheraton)
2:45 PM - LL2.1
Mechanical and Elastic Property Evaluation of n and p-Type Skutterudites.
James Salvador 1 , Jung Cho 1 , Jihui Yang 2 , Andrew Wereszczak 3 , Hsin Wang 3
1 Chemical Sciences and Materials Systems Laboratory, GM Global Research, Warren, Michigan, United States, 2 Electrochemical Energy Research Laboratory, GM Global Research, Warren, Michigan, United States, 3 Materials Science and Technology Division, Oakridge National Lab, Oakridge, Tennessee, United States
Show AbstractSkutterudites have emerged as a front-runner for applications in medium to high temperature thermoelectric based waste heat recovery. Skutterudites offer a great compromise of good thermoelectric performance and mechanical and chemical stability as well as being composed of relatively abundant and benign starting materials. In this contributed talk we will discuss the mechanical and elastic properties of these compounds and the materials processing steps used to obtain them. Fracture strength was determined at room and elevated temperatures using a custom made three-point bend ceramic test fixture capable of rapid sample analysis at elevated temperatures while providing an environment isolated from ambient atmosphere. The results will be discussed in terms of module design and resulting durability under operating conditions.
3:00 PM - **LL2.3
Are Skutterudites Phonon Crystals or Phonon Glasses?
Jihui Yang 1 , Xun Shi 2 , Hsin Wang 4 , Miaofang Chi 4 , James Salvador 1 , Jiong Yang 2 , Shengqiang Bai 2 , Wenqing Zhang 2 , Lidong Chen 2 , John Copley 3 , Juscelino Leao 3 , John Rush 5
1 , GM R&D Center, Warren, Michigan, United States, 2 , Shanghai Institute of Ceramics, Shanghai China, 4 , Oak Ridge National Lab, Oak Ridge, Tennessee, United States, 3 NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland, United States, 5 , University of Maryland, College Park, Maryland, United States
Show AbstractOver the past decade the Phonon-Glass-Electron-Crystal concept has played an important role in the understanding and design of highly efficient thermoelectric materials. Caged compounds such as skutterudites and clathrates, with occupied voids, have been assumed to be phonon-glasses with low lattice thermal conductivity but there has been no direct experimental evidence to confirm this hypothesis, and the idea has recently been challenged. In this presentation we present a combined inelastic neutron scattering, scanning transmission electron microscopy, and thermoelectric properties study of selected multiple-filled skutterudites with partial void occupancy. Our results unambiguously show that these materials exhibit phonon-glass behavior, due to the combined effects of sufficiently random spatial distribution and wide-spectrum phonon scattering by the filler atoms, which behave as phase-incoherent Einstein oscillators. These factors result in minimum lattice thermal conductivity and remarkable thermoelectric performance.
3:30 PM - LL2.4
Temperature-dependent Thermal Expansion and Elastic Moduli of Skutterudite Thermoelectric Materials.
Robert Schmidt 1 , Eldon Case 1 , Bradley Wing 1 , Rosa Trejo 2 , Edgar Lara-Curzio 2 , E. Payzant 2 , Roberta Peascoe-Meisner 2 , Edward Timm 3
1 Materials Science Engineering, Michigan State University, East Lansing, Michigan, United States, 2 High Temperature Materials Laboratory, Oak Ridge National Laboratory, Oak Ridge, Kentucky, United States, 3 Mechanical Engineering, Michigan State University, East Lansing, Michigan, United States
Show AbstractPowder processed specimens of antimony-based skutterudite thermoelectric material were hot pressed and cut into specimens by diamond saw. SEM micrographs of polished surface, thermally etched surface, and fractured surface were used to determine the microstructure of the densified specimens. The thermal expansion coefficient was determined from room temperature to 723K using a ThermoMechanical Analyzer (TMA) and by x-ray diffraction. The temperature dependent elastic moduli were measured by Resonant Ultrasound Spectroscopy (RUS) from room temperature to 773K. Using the elasticity and thermal expansion data, the thermally induced stresses may be estimated as a function of temperature.
4:15 PM - LL2.5
Electron-phonon Interactions in AE-Ga-(Ge,Si) Clathrates (AE=Sr and Ba).
Katsumi Tanigaki 1 2 , Jingtao Xu 1 , Jun Tang 1 , Khuong Huynh 2 , Yoichi Tanabe 1 , Satoshi Heguri 2
1 WPI, Tohoku University, Sendai Japan, 2 Physics, Graduate of Science, Tohoku University, Sendai Japan
Show AbstractRattling phonons have so far been the priority researches in clathrates as the issues of acoustic phonon scattering as well as electron-phonon interactions for enhancing effective mass of conduction electrons in controlling physical properties. The former can help for suppressing heat conductivity in keeping high electric conductivity and the latter contribute increasing Seebeck coefficient, and therefore these factors make clathrate compounds one of the very promising materials for high efficient thermoelectric conversion with a large dimension less figure of merit. These unique phonons are produced via anharmonic motions of the atomic elements endohedrally accommodated inside the polyhedra in clathrate structure, and therefore should be discussed in comparison with lattice phonons and intra-cluster phonons [1-3]. Among clathrate compounds, AE-Ga-Ge ternary system clathrates (AE=Sr, Ba, Eu) have been drawing much attention because the carrier concentration can be controlled nearly in the semiconducting regime and thus provide a relatively large S coefficient, and heat conductivity can be smaller by showing a glass-like behavior when the small elements are accommodated. In this talk we have elucidate how large the electron-phonon interactions when rattling anharmonic phonons are involved using single crystals with various carrier concentrations[4-5]. We will present the accurate effective masses for both SGG (AE=Sr) and BGG (AE=Ba) using heat capacity measurements in a wide range of energy scale. Our analyses ambiguously show that the electron-phonon interaction can be enhanced when the anharmonic rattling phonon is involved. In addition, we discuss the origin of glass-like behavior in AE-Ga-(Ge,Si) clathrates from the experiments obtained by core-level soft X ray spectroscopy in a high energy facility.[1] K. Tanigaki, et al., Nature Materials, 2, 653 (2004). [2] T. Rachi, K. Tanigaki et al., Chem. Phys. Letters, 409, 48 (2005). [3] T. Rachi, K. Tanigaki et al., Phys. Rev. B, 72, 144504 (2005). [4] J. Tang, T. Rachi, K. Tanigaki et al., Phys. Rev. B, 78, 085203 (2008).[5] J. Tang, K. Tanigaki et al., Chem. Phys. Lett. 472, 60 (2009).
4:30 PM - LL2.6
Thermal Transport in Cage-like Structures.
Mona Zebarjadi 1 , Keivan Esfarjani 1 , Boris Kozinsky 3 , Jian Yang 2 , Zhifeng Ren 2 , Gang Chen 1
1 Mechanical Engineering, MIT, Cambridge, Massachusetts, United States, 3 Research and Technology Center, Robert Bosch LLC, Cambridge, Massachusetts, United States, 2 Physics Department, Boston College, Chesnut Hill, Massachusetts, United States
Show AbstractThe relation between the thermal conductivity of cage like structures with crystal parameters are investigated using a two dimensional toy model. The model consists of host atoms on a rectangular lattice with fillers at the center of each rectangle. The thermal conductivity is calculated by using Green- Kubo equilibrium molecular dynamics simulations. It is generally believed that the smaller and the heavier the filler, the lower is the thermal conductivity. We show that the thermal conductivity decreases with atomic displacement parameter while it has local minima versus filler mass. Similar trends were observed in experiments on skutterudites. The trends are explained by analyzing the effect of the filler on the phonon dispersion and relaxation times of the host material. Our study shows that it is very important to include the correct band dispersion (group velocities) to get the right features of the thermal conductivity. To demonstrate this further, the mean free paths of real skutterudite materials are calculated and the results of the Debye+ Einstein model are compared with those of the first principle calculations and the experimental data.
4:45 PM - LL2.7
Multiple Filler Skutterudites: CezInxYbyCo4Sb12 Posses High Figure of Merit.
Jennifer Graff 1 , Song Zhu 2 , Timothy Holgate 1 , Jiangying Peng 3 , Jian He 2 , Terry Tritt 2
1 Material Science and Engineering, Clemson University, Clemson, South Carolina, United States, 2 Physics and Astronomy, Clemson University, Clemson, South Carolina, United States, 3 School of Mechanical Science & Engineering, Huazhong University of Science & Technology, Wuhan China
Show AbstractSkutterudites have been approached in the last decade as one of the future state of the art materials which have motivated research on the concept of energy conversion, or more specifically the field of thermoelectrics. The ability to tune a skutterudites electrical and thermal transport properties have been proven successful in single-filled, double-filled, and multiple-filled skutterudites. This article will focus on multiple-filled skutterudites, CezInxYbyCo4Sb12 (0 ≤ (x, y, z) ≤ 0.2). Indium was attempted to be inserted as a filler but results seem to indicate that it is substituting on the Sb sites. The samples were prepared via melt-annealing-sintering technique and were characterized by X-ray powder diffraction, thermal and electrical transport properties, specific heat, Hall coefficients, scanning electron microscopy within the temperature range of 10-800K. Results from the thermoelectric property measurements indicate a high ZT over a temperature regime of approximately 500-800K as well as a maximum ZT of 1.4 around 800K.
5:00 PM - LL2.8
Thermoelectric Properties of Double-filled Skutterudite Thin Films Grown by Pulsed Laser Deposition.
Sarath Kumar 1 , Ahmed Alyamani 2 , J. Graff 3 , Terry Tritt 3 , Husam Alshareef 1
1 Materials Science and Engineering, KAUST, Thuwal Saudi Arabia, 2 Nanotechnology Centre, King Abdul Aziz City for Science and Technology, Riyadh 11442 Saudi Arabia, 3 Department of Physics and Astronomy, Clemson University, South Carolina 29634, South Carolina, United States
Show AbstractIn the present work, we report the growth of In0.2Yb0.2Co4Sb12 double filled skutterudite thin films onto SiO2, MgO and Si/SiO2 substrates by pulsed laser deposition under different conditions. Grazing incidence X-ray diffraction of the films have revealed that single phase skutterudite films are formed only under optimized conditions of deposition, at a substrate temperature of 525 K. Raman spectroscopy studies have been performed to confirm the formation of the skutterudite phase. It has been observed that the presence of argon during deposition results in formation of predominant secondary phases. The surface morphology of the films has been analyzed using atomic force microscopy and transmission electron microscopy. The Seebeck coefficient and electrical resistivity of the films on different substrates have been measured in the temperature range 300-1200 K using the Ozawa Seebeck tester. The Seebeck coefficient of the films was negative indicating n-type conduction. It has been observed that the electrical conductivity and the absolute Seebeck coefficient of the films increase with increase in temperature. A respectable power factor of 4 µW/K2.cm has been obtained. Furthermore, strategies to enhance the power factor are discussed.
5:15 PM - LL2.9
Transport Properties of Partially-filled Single Crystal Type II Si Clathrates.
Stevce Stefanoski 1 , George Nolas 1
1 Physics, University of South Florida, Tampa, Florida, United States
Show AbstractInorganic clathrates are "open-structured" materials in which a covalently bonded frameworks enclose metal atoms in atomic cage-like polyhedra. Intermetallic clathrates are actively investigated because of their potential for thermoelectric applications. Thus far clathrates with the type I and VIII crystal structure have been investigated, while a more systematic investigation of the physical properties of type II clathrates has yet to be undertaken. Moreover, to get a better understanding of the intrinsic properties of these materials, investigations on single crystals is ideal. In this work we present structural and transport properties of single crystal type II "partially filled" Si clathrates. Whereas fully filled Na24Si136 clathrates show metallic behavior, a metal-to-insulator transition is expected upon reducing the Na content below 33 % of full filling. This approach may offer a potentially new direction in the search for novel materials for thermoelectric applications.
5:30 PM - LL2.10
Different Physical Properties in n/p-type Ba8Ga16Ge30.
Jingtao Xu 1 , Jun Tang 1 , Hitoshi Heguri 2 , Yoichi Tanabe 1 , Katsumi Tanigaki 1 2
1 WPI AIM-Research, Tohoku University, Sendai Japan, 2 Department of Physics, Tohoku University, Sendai, Miyagi, Japan
Show AbstractClathrate compounds have attracted much attention as potential thermoelectric materials because of the low thermal conductivity and the large thermopower. Among a large number of clathrate types, type I clathrates M8Ga16Ge30 (M = Ba, Sr, and Eu) have been most extensively explored. The unit cell consists of two Ga-Ge dedecahedra and six tetrakaidecahedra, which can accommodate two and six M guest atoms, respectively. When the size of guest atoms decrease from Ba to Eu, the thermal conductivity is greatly suppressed and changes from a crystal-like behavior to a glass-like behavior. So far, all samples of Eu8Ga16Ge30 (EGG) and Sr8Ga16Ge30 (SGG) are of n-type except for Ba8Ga16Ge30 (BGG). The change of carrier type in BGG results in completely different thermal conductivity. The thermal conductivity of the n-type sample has a pronounced peak at about 20 K, as in a typical crystalline material. On the other hand, the thermal conductivity of the p-type sample shows glass-like behavior, being similar to that for EGG and SGG. This glass-like behavior in EGG and SGG is believed to originate from the tunneling effect of the off-centered guest atoms. However, further neutron diffraction studies on n/p-type BGG single crystals showed that the differences in thermal conductivity do not result from different off-centered displacement of the guest atoms. Therefore, the reason for the different behaviors remains to be one of the most curious questions in clathrate compounds. In this presentation, we will discuss the important physical parameters useful for having reasonable explanations, based on our XPS, transport and susceptibility measurements. [1] J. Tang, R. Kumashiro, J. Ju, Z. Li, M. A. Avila, K. Suekuni, T. Takabatake, F. Guo, K. Kobayashi, K. Tanigaki, Chemical Physics Letters, 472, 2, 6-64, (2009).[2] J. Tang, T. Rachi, R. Kumashiro, M. A. Avila, K. Suekuni, T. Takabatake, FZ. Guo, K. Kobayashi, K. Aoki and K. Tanigaki, Phys. Rev. B, 78, 085203-085206 (2008).
5:45 PM - LL2.11
Lattice Thermal Transport from First-principles: Role of Higher Order Phonon Processes.
Dmitri Volja 1 , Boris Kozinsky 2 , Jivtesh Garg 1 , Nicola Marzari 1 , Marco Fornari 3
1 DMSE, MIT, Cambridge, Massachusetts, United States, 2 Research and Technology Center, ROBERT BOSCH LLC, Cambridge, Massachusetts, United States, 3 Department of Physics, Central Michigan University, Mount Pleasant, Michigan, United States
Show AbstractThermal transport is a fundamental quantity in the field of thermoelectricity. Accurate theoretical prediction of thermal conductivity is crucial for design of new highly efficient thermoelectric materials. In the most promising systems heat is primarily carried by the lattice vibrations, and anharmonicinteractions are responsible for the finite thermal conductivity. Within density-functional perturbation theory one can, in principle, evaluate completely ab-initio these phonon interactions. However, for most materials evaluation of such interactions from first-principles is currently a formidable task. In this work we analyze third order phonon-phonon scattering mechanisms that arise from the anharmonicity of interatomic interactions, and use a Boltzmann transport approach to estimate thermal conductivity. In our methodology we combine first-principles determination of interatomic force constants with empirical models potentials to calculate higher order response terms. The scheme is extended further within perturbation theory to evaluate numerically four-phonon processes. We validate this approach by testing the approximations in simple systems like silicon, where full evaluation of anharmonic force constants from first principles is possible. Finally, we apply the approach to optimize performance of complex thermoelectric materials, such as skutterudites.