Bulletin of the American Physical Society
APS March Meeting 2023
Volume 68, Number 3
Las Vegas, Nevada (March 5-10)
Virtual (March 20-22); Time Zone: Pacific Time
Session B45: Energy - Thermoelectrics |
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Sponsoring Units: GERA Chair: Sanjoy Mukhopadhyay, Mission Support and Test Services, inc., LLc Room: Room 315 |
Monday, March 6, 2023 11:30AM - 11:42AM |
B45.00001: Thermal transport in Weyl semimetal BaMnSb2: a first-principles study YUBI CHEN, Rongying Jin, Bolin Liao, Sai Mu Orthorhombic BaMnSb2 is a topological semimetal consisting of alternative stacking of Sb, Ba, and MnSb layers. A recent experiment revealed a low thermal conductivity and a modest thermal power of BaMnSb2, suggesting that BaMnSb2 could be a promising thermoelectric material. Employing density functional theory, we perform an in-depth investigation of the electronic structure, phononic structure, and thermal transport of BaMnSb2, addressing the effect of Coulomb repulsion and spin-orbit coupling. We find that the phonon band structure of BaMnSb2 is insensitive to the Coulomb repulsion, spin-orbit coupling, and even long-range magnetic ordering. Assessing the three-phonon scattering, a low and highly anisotropic lattice-mediated thermal conductivity of BaMnSb2 is observed from our calculations. Thermal power is also calculated by the semiclassical Boltzmann theory with a constant relaxation time approximation. Avenues to enhance the thermal power and lower the thermal conductivity of BaMnSb2 will be discussed including doping and mechanical strain. |
Monday, March 6, 2023 11:42AM - 11:54AM |
B45.00002: Thermoelectric Effect in a Topological Dirac Semimetal under Strain and Confinement Wenkai Ouyang, Alexander C Lygo, YUBI CHEN, Dung D Vu, Brandi L Wooten, Joseph P C Heremans, Susanne Stemmer, Bolin Liao The topological Dirac semimetal Cd3As2 is a potential thermoelectric material due to its high electron mobility and low lattice thermal conductivity. However, in its bulk form, Cd3As2 has no band gap, which is detrimental for the thermopower. One way to open a band gap in the bulk is through quantum confinement and strain in thin films. In this project, we investigate and contrast the thermoelectric properties of epitaxial Cd3As2 films with two different thicknesses (950 nm and 95 nm). Resistivity and quantum oscillation measurements established the semimetal nature of the thick sample, while the thin sample showed semiconducting features, suggesting the presence of a bulk gap, likely due to epitaxial strain and a weak confinement effect. The thermoelectric properties of these samples were qualitatively different. The thick sample exhibited a semi-metallic behavior, where its Seebeck coefficient can be fitted by a semiclassical model, while a sign change of the Seebeck coefficient was observed in the thin sample at low temperatures. In addition, the Nernst coefficient of the thick sample showed a dispersive (Drude-like) peak versus the magnetic field and an anomalous Nernst effect appeared below 50 K, in agreement with previous bulk measurements. In contrast, the thin sample showed a monotonically increasing Nernst coefficient versus magnetic field and an absence of anomalous Nernst effect down to 2 K. Our results open possibilities for engineering the thermoelectric properties of topological semimetals through strain and quantum confinement effect. |
Monday, March 6, 2023 11:54AM - 12:06PM |
B45.00003: Exploring best thermoelectric efficiency from of more than 104 explored thermoelectric materials and 108 device efficiency calculations Byungki Ryu, Jaywan Chung, Masaya Kumagai, Yukari Katsura, SuDong Park A thermoelectric device is a heat engine that directly converts thermal energy into electrical energy through the Seebeck and Peltier effects. More than tens thousands thermoelectric materials have been reported and numerous high ZT materials have been developed. However, the achievable thermoelectric efficiencies are not known for explored thermoelectric materials. Here, we report the theoretical best thermoelectric efficiencies of each thermoelectric material in a large materials dataset (Starrydata2 thermoelectric web DB [1]). The dataset was filtered to remove erroneous data, and thermoelectric material and device efficiencies were computed by solving the thermoelectric integral equations [2]. The achievable theoretical efficiencies were explored for various thermal and electrical conditions, i.e., over 1,615,713 material efficiency data and 97,841,810 device efficiency data. Finally, the achievable best thermoelectric efficiencies were calculated: 33% at the side temperature (Th) of 1400 K for an infinite cascade device, 24% at Th = 1100 K for a multistage P-N leg pair device, and 17% at Th = 860 K for a single-stage P-N leg device. This study highlights the gap between theoretical material performance and experimental device performance in thermoelectric power generation. The result of this work cab be found in arXiv:2210.08837 [3]. |
Monday, March 6, 2023 12:06PM - 12:18PM |
B45.00004: Exploration of 17-electron TixCoySnz thin film spreads for thermoelectric properties via combinatorial approach Rohit Pant, Dylan J Kirsch, Suchismita Sarker, Nathan Johnson, Thomas Wynn, Joshua Martin, Apurva Mehta, Ichiro Takeuchi Most of the known thermoelectric materials are 18-electron systems owing to their compositional stability. However, the synthesis of a 17-electron thermodynamically stable thermoelectric material is extremely important, especially when many predictions confirm that they might have important thermoelectric properties. In the present work, we deposited TixCoySnz (a 17-electron system) thin films using a combinatorial sputtering approach because it provides an efficient route to synthesize a wide range of stoichiometries on a single substrate, enabling its rapid screening. These films consisted of both half Heusler (HH) and full Heusler (FH) domains of TixCoySnz in the combi matrix, with a total of 177 different compositions. Their compositional, structural, and electrical properties were characterized using high-throughput characterization techniques. The power factor analysis shows that instead of exact HH or FH composition, better electrical properties are found near the slightly Co and Ti-rich regions. High throughput synchrotron measurements of these spreads reveal an overall high crystallinity, with large single-phase domains around HH and FH regions. We report the highest Seebeck coefficient of ~-39.60 mV/K with atomic ratios of ~Ti0.37Co0.34Sn0.29, near the HH composition. Whereas the highest power factor was ~4.72 mW/cmK2 for atomic ratios of ~Ti0.19Co0.67Sn0.14, which surprisingly is near the FH composition. |
Monday, March 6, 2023 12:18PM - 12:30PM |
B45.00005: Compositional design toward universal band convergence for high-performance Zintl thermoelectrics Xin Shi, Shaowei Song, David J Singh, Zhifeng Ren Band convergence can impact the thermoelectric performance of materials in a positive manner, but seeking the composition that shows such a feature in a series of alloys remains a time-consuming task. Here we propose, for the first time, a novel and effective method to design a series of compositions at one time, with Zintl materials as a case to study, where valence band convergence is presumably realized in all these compositions. Validity of this presuming design is subsequently testified from both experimental and theoretical standpoints. In addition, we define a new parameter to Zintl compounds, termed “number of aligned pairs”, and its effect on electrical properties of the materials is investigated. Finally, benefiting from such a design, good thermoelectric performance is universally achieved in these compositions, the best among which, furthermore, exhibits a peak zT that turns out to be one of the highest in all reported p-type Zintls to date. By pairing it with an outstanding n-type material, a thermoelectric module for power generation is assembled, and has demonstrated its potential for enabling heat-to-electricity energy conversion with high efficiency. |
Monday, March 6, 2023 12:30PM - 12:42PM |
B45.00006: Device-level optimization of n-type Mg3(Sb, Bi)2-based thermoelectric modules toward applications Congcong Xu, Zhongxin Liang, Shaowei Song, Zhifeng Ren The performance of thermoelectric materials has been significantly increased in recent decades, making the concept of generating energy from waste heat or enhancing refrigeration more feasible. N-type Mg3(Sb, Bi)2 material is one of the most popular and commercially promising materials in the thermoelectric family, however, there are significant challenges at the device level toward large-scale applications. First, it is always challenging to maintain high zT values over a wide temperature range. Second, the zT of the material is not directly equivalent to the zT of the device because the real zT of the device is affected by the contact resistances at the junctions. Third, reliability and durability issues are concerns since they critically determine the service life of the devices. Fourth, proper structure design, including size match of the n- and p-type thermoelectric legs, heat exchange, and space utilization, is crucial to the device’s performance since its efficiency is sensitive to its dimensions. Finally, the manufacturing costs of thermoelectric devices are equally important when considering large-scale applications. In short, the figure of merit zT is of great significance as a core parameter to guide the improvement of thermoelectric materials while the thermoelectric field must look far beyond the simple goal of pursuing high zT. Here, we focus on n-type Mg3(Sb, Bi)2-based thermoelectric modules and try to find out the influence of various parameters on the module and device-level optimization strategies to solve practical application issues. |
Monday, March 6, 2023 12:42PM - 12:54PM |
B45.00007: Origins of ultralow thermal conductivity in mixed-ion-electron conductor KAg2SbS4 Sevan Chanakian, Bonnie Stolt, Junsoo Park, Yining He, Wei Lai, Alexandra Zevalkink Promising thermoelectric materials exhibit high electrical conductivity and low thermal conductivity. Recent reports of ternary and quaternary diamond-like semiconductors (DLSs) that exhibit low thermal conductivity while maintaining their high electrical conductivity have sparked interest in DSLs for potential thermoelectric candidates. Here we present the experimental properties of another promising DSL compound, KAg2SbS4, which exhibits exceptionally low lattice thermal conductivity (0.55 W/mK). In the present work we employ experimental methods (namely XRD, resonance ultrasound spectroscopy, and impedance spectroscopy) and density functional theory (DFT) theory to understand the structural and ionic origins of the ultra-low thermal conductivity in KAg2SbS4. Phonon calculations suggest that the ultralow thermal conductivity in this material arises from the severely distorted tetrahedral coordination environment of the K atoms, as well as soft, low velocity modes associated with Ag displacement. Additionally, we demonstrate that KAg2SbS4 exhibits high ionic conductivity, which may also be responsible for additional phonon-scattering in this material. |
Monday, March 6, 2023 12:54PM - 1:06PM |
B45.00008: Bond heterogeneity, lone pairs, and ultralow thermal conductivity: the story of aikinites Marco Fornari, Shriparna Mukherjee, Virginia Carnevali, David J Voneshen, Krishnendu Maji, Emmanuel Guilmeau, Anthony V Powell, Paz Vaqueiro Large-scale production of thermoelectric devices requires the discovery of high-performance materials, which are low cost [PV1] and based on abundant elements in the Earth crust. In this context, sulfide minerals, such as CuPbBiS3, are a promising class of thermoelectric materials. Of special interest are materials that can provide, with minor modifications, the p-type and n-type legs of the thermocouple, to ensure compatibility. To this goal we have investigated the structural, electronic and vibrational properties of aikinite and copper-deficient aikinite Cu1–xPb1–xBi1+xS3 (0 ≤ x ≤ 1). Our work encompasses synthesis, powder X-ray and neutron diffraction, electronic and thermal transport properties, inelastic neutron scattering, and first-principles molecular dynamics calculations. We have established that these materials are semiconductors that can be doped p- or n-type. We have assessed the bond heterogeneity and the role of Pb and Bi lone-pairs on the thermal transport and will discuss how these features lead to an exceptionally low thermal conductivity of 0.48 W m-1 K-1 at 573 K. |
Monday, March 6, 2023 1:06PM - 1:18PM |
B45.00009: Enhanced Thermoelectric Properties of YbCo2Zn20 through Charge Carrier Tunning Jorge R Galeano-Cabral, Benny c Schundelmier, Olatunde Oladehin, Keke Feng, Juan Ordonez, Ryan E Baumbach, Kaya Wei There is a growing interest in utilizing waste-heat recovery units to enhance the efficiency of energy processes, and thermoelectric generators (TEGs) are sound candidates since they convert heat directly into electricity by using the Seebeck effect. Extensive studies have been conducted to make TEGs feasible in reality, but thermoelectric technology is still far from being widely employed in practical applications due to the low figure of merit (ZT) for most thermoelectric materials. However, promising low-temperature thermoelectric properties have been reported for single crystals of YbTM2Zn20 (TM = Co, Rh, Ir) [1, 2]. Here we report a detailed study on the effect of charge carrier tuning for the YbCo2Zn20 compound. Guided by the Hall effect measurement, we are able to quantitively dope on the Co site. This leads to improved electrical properties as well as enhanced ZT values. In addition, more efficient phonon scatterings are achieved through this approach which lowers the lattice thermal conductivity for these materials. |
Monday, March 6, 2023 1:18PM - 1:30PM |
B45.00010: Thermoelectric properties of a metastable (Ba,K)Zn2As2 crystallized in the ThCr2Si2-type structure Chul-Ho Lee, Haruno Kunioka, Kunihiro Kihou, Satoshi Tsutsui We obtained a high temperature β-phase of Ba1−xKxZn2As2 crystallized in the ThCr2Si2-type structure as a metastable state at a room temperature by quenching. It's thermoelectric properties were evaluated in the range of 0.00 ≤ x ≤ 0.10. The maximum dimensionless figure-of-merit ZT was relatively high for a ThCr2Si2-type structure to be ZT = 0.30 at 773 K for x = 0.03 with the lattice thermal conductivity of less than 1 W/mK. The quite low lattice thermal conductivity could be attributed to lattice instability between the β-phase and the equilibrium α-phase crystallized in the α-BaCu2S2-type structure. The stability of the metastable β-phase was examined by powder X-ray diffraction measurements over a wide temperature range. Phase diagram of the metastable β-phase was determined and temperature dependence of its atomic parameters was obtained by Rietveld analysis. The results demonstrate the potential of compounds crystallized in the ThCr2Si2-type structure and the effectiveness of a metastable state for achieving a high-performnace thermoelectric-property. |
Monday, March 6, 2023 1:30PM - 1:42PM |
B45.00011: Challenges and solutions in Mg3Sb2-based thermoelectric materials toward applications: thermal stability and the performance-matched p-type Zhongxin Liang, Congcong Xu, Shaowei Song, Xin Shi, Zhifeng Ren Mg3Sb2-based n-type thermoelectric materials have gained considerable interest for both power production and cooling applications because of their high zTs over a wide temperature range, mechanical robustness, and low cost. However, substituting commercial Bi2Te3 alloys with Mg3Sb2 in real applications remains challenging. On the one hand, the unsatisfactory thermal stability originating from significant Mg loss at high temperatures hinders their large-scale application; on the other hand, an ideal p-type compound with matched thermoelectric performance and thermodynamic properties has not been reported, making it difficult to construct a thermally reliable and low-cost thermoelectric module. In order to solve these issues, we first developed a simple cation-site doping strategy to enhance the thermal stability of n-type Mg3Sb2 through the suppression of Mg vacancy formation. Second, a high zT of 0.7 was achieved in p-type Mg3Sb2, allowing the construction of an all Mg3Sb2-based unicouple with a maximum conversion efficiency of 5.5% at the hot-side temperature of 573 K. Given the enhanced thermal stability and high performance of p- and n-type compounds, Mg3Sb2-based materials are promising candidates for next-generation thermoelectric devices. |
Monday, March 6, 2023 1:42PM - 1:54PM |
B45.00012: Theory of thermoelectric effect based on antiferromagnetic magnon drag in natural chalcopyrite Cu1+xFe1−xS2 Masao Ogata, Hiroyasu Matsuura, Naohito Tsujii, Takao Mori In natural chalcopyrite mineral, Cu1+xFe1−xS2 (x = 0.08), a huge Seebeck effect was reported around the room temperature [R. Ang, et al., Angew. Chem. 54, 1 (2015)]. We study the mechanism of this Seebeck effect and clarify that the observed huge Seebeck coefficient will be due to the antiferromagnetic magnon drag collaborated with the impurity band. First, we show that the temperature dependences of the electrical resistivity and Hall coefficient can be reproduced by the theoretical calculation based on self-consistent t-matrix approximation which can consider the impurity band. Second, by deducing the lifetime of magnon from the experimental result of thermal conductivity, we evaluate the Seebeck coefficient due to the antiferromagnetic magnon drag by the linear response theory of Kubo-Luttinger. We find that the obtained theoretical result is quantitatively consistent with the experimental one near the room temperature. |
Monday, March 6, 2023 1:54PM - 2:06PM |
B45.00013: Thermoelectric properties of RbZn4As3 Keigo Ono, Ryosuke Sakagami, Kunihiro Kihou, Yosuke Goto, Chul-Ho Lee Zintl phase compounds are one of the most famous systems of thermoelectric materials. In particular, Sb-based 122-Zintl compounds have been intensively explored, resulting in finding many new thermoelectric materials that the dimensionless figure-of-merit (ZT) exceeds the value of 1. On the other hand, we have found high performance thermoelectric materials in As-based Zintl compounds [1-3]. Although lighter atomic mass of As than Sb is a disadvantage in terms of the lattice thermal conductivity, those exhibit low thermal conductivity. Recently, we have found that As-based 143-Zintl compounds of NaZn4As3 exhibit extremely low lattice thermal conductivity [4]. Because it consists of double conduction layers, higher carrier mobility than 122 compounds could be expected. |
Monday, March 6, 2023 2:06PM - 2:18PM |
B45.00014: Compact and Efficient Thermoelectric Nanogenerator Platform in MoS2 Seungil Baek, Euicheol Shin, Ho-Ki Lyeo, Sanghee Cho, Yong-Hyun Kim A thermoelectric generator (TEG) suffers from low efficiency and the expensive cost of the base material. Miniaturizing TEG suffers from the demand that separation between p-type and n-type leg is crucial to avoid interface carrier recombination which severely degrades the efficiency. Here, we propose the Seebeck domain where the local Seebeck coefficient stays flat to some extent even though the wave function decays exponentially. In the MoS2 5|7 grain boundary system, ab initio scanning Seebeck microscope detected that localized charge at the defect sites modifies the local Seebeck profile which broadens out to the nanoscale. Independent control of the Seebeck domain can be readily achieved by appropriate doping conditions, which provides nanoscale applicability for thermoelectric power generation. The potential barrier at the junction is built upon oxygen substitution which realizes a nanoscale homojunction triboelectric generator. Our findings contribute to the field of thermoelectricity by providing a compact and efficient thermoelectric platform with easily-accessible materials. |
Monday, March 6, 2023 2:18PM - 2:30PM |
B45.00015: Silicon Micro-Thermoelectric Coolers For Local Heat Removal In Integrated Circuit Chips Mark Lee, Ruchika Dhawan, Hal Edwards High performance Si integrated circuits (ICs) can generate heat fluxes ≥ 100 Wcm–2 over areas ~ 10–4 cm2. This heating degrades IC performance and produces significant excess heat. Currently chip cooling and waste heat removal is done by air conditioning, which is inefficient, wasteful, and expensive because it globally cools everything, not just the IC chips. As a result data centers now consume ~ 1% of worldwide annual electrical energy production, estimated to increase to ~ 3% by 2030. In an effort to reduce thermal management energy requirements, we have developed Si micro-thermoelectric coolers (μTECs) that can be integrated in-chip using the same process flow used to make an IC. These μTECs have been made with areas as small ~ 10–5 cm2 and can be inserted directly below or in close proximity to known local hot spots in an IC. While Si µTECs cannot achieve low base temperatures, they can actively pump relatively high heat fluxes directly to a heat sink, thus preventing or minimizing on-chip temperature increases. In this way only the heat sink rather than an entire room needs to be macroscopically cooled, potentially resulting in a significant reduction in energy usage. Prototype integrated μTECs have been shown to pump in-chip generated heat fluxes of 45 Wcm–2 with no increase in local chip temperature. Models suggest that improvements in μTEC design can lead to maximum cooling power densities > 100 Wcm–2. |
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