Bulletin of the American Physical Society
APS March Meeting 2015
Volume 60, Number 1
Monday–Friday, March 2–6, 2015; San Antonio, Texas
Session B12: Focus Session: New Thermoelectic Materials |
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Sponsoring Units: DMP/DCOMP GERA FIAP Chair: Jihui Yang, University of Washington Room: 007C |
Monday, March 2, 2015 11:15AM - 11:27AM |
B12.00001: Investigation of InSb-In$_{2}$XTe (X$=$Ge {\&} Sn) pseudo binary alloys as potential thermoelectric materials* Vijayabarathi Ponnambalam, Donald T. Morelli Crystallizing in the zinc blende structure, InSb is known for promising thermoelectric properties with carrier mobility as high as $\sim$ 10$^{4}$ cm$^{2}$/V s at 300 K. However, the main drawback is its exceptionally high thermal conductivity $\sim$ 20 W/m K at 300 K. In this regard, pseudo binaries InSb-In$_{2}$XTe (X$=$Ge {\&} Sn) hold the promise of offering reduced thermal conductivity while maintaining the other thermoelectric properties intact. A series of InSb-In$_{2}$XTe type alloys has been synthesized. Thermal and electrical transport properties have been studied, and the results will be discussed with an emphasis on how the thermal conductivity is affected by the concentration of solute atoms. \\[4pt] *This work was supported as part of the Center for Revolutionary Materials for Solid State Energy Conversion, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Award Number DE-SC0001054. [Preview Abstract] |
Monday, March 2, 2015 11:27AM - 11:39AM |
B12.00002: Study on thermoelectric performance by Na doping in nanostructured Mg$_{1-x}$Na$_{x}$Ag$_{0.97}$Sb$_{0.99}$ Jing Shuai, Hee Seok Kim, Yucheng Lan, Shuo Chen, Yuan Liu, Huaizhou Zhao, Jiehe Sui, Zhifeng Ren MgAg$_{0.97}$Sb$_{0.99}$ was found to be potentially a new class of thermoelectric materials with \textit{ZT} values above 1 in the temperature from 100 to 300 $^{\circ}$C. In this report, we systematically studied the effect of Na doping in Mg, Mg$_{1-x}$Na$_{x}$Ag$_{0.97}$Sb$_{0.99}$, on the thermoelectric properties and found Na was effective to increase the carrier concentration and power factor, especially below 180 $^{\circ}$C, which led to higher \textit{ZT} values, a better self-compatibility factor, and ultimately a higher output power at the optimal Na concentration of x $=$ 0.005-0.0075. [Preview Abstract] |
(Author Not Attending)
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B12.00003: Enhancement of thermoelectric performance by phase seperation of Ag$_{2}$Te in quaternary Ag$_{\mathrm{x}}$Bi$_{0.5}$Sb$_{\mathrm{1.5-x}}$Te$_{\mathrm{3-x}}$ Yoo Jang Song, Jong-Soo Rhyee, Bong Seo Kim, Su Dong Park, Jae Hoon Jung, Byung-Gil Ryu, Jong Rae Lim Quaternary Ag--Bi--Sb--Te alloys with the general formula of Ag$_{x}$Bi$_{0.5}$Sb$_{1.5-x}$Te$_{3-x}$ are synthesized by solid state reaction for the high Ag doping x$=$0.1, 0.2, and 0.3. The powder x-ray diffraction analysis of the melted ingot shows the phase separation of AgSbTe$_{2}$ and Bi$_{0.5}$Sb$_{1.5}$Te$_{3}$ phases. After the hot press sintering at 350 ${^\circ}$, we found Ag$_{2}$Te/Bi$_{0.5}$Sb$_{1.5}$Te$_{3}$ composite, instead of AgSbTe$_{2}$ phase separation, from the energy dispersive x-ray spectroscopy and x-ray diffraction measurements. The electrical conductivities of the Ag$_{2}$Te/Bi$_{0.5}$Sb$_{1.5}$Te$_{3}$ composite are significantly increased comparing with that of conventional $p$-type Bi$_{0.5}$Sb$_{1.5}$Te$_{3}$ compound, implying that the interface effect by phase separation can attribute to the increase of electrical conductivity. The maximum power factor and \textit{ZT} values are reached up to 2.1 mW K$^{-2}$ m$^{-1}$ ($\sim$ 400 K) and 1.1 (at 570 K), respectively, for x $=$ 0.1 composite.. Here we propose that the phase separation of Ag$_{2}$Te in Bi$_{0.5}$Sb$_{1.5}$Te$_{3}$ matrix can increase thermoelectric performance at mid-temperature temperature range. [Preview Abstract] |
Monday, March 2, 2015 11:51AM - 12:27PM |
B12.00004: Some Interesting Physics in Tetrahedrite-Based Thermoelectrics Invited Speaker: Donald Morelli Thermoelectric materials require a unique combination of fundamental thermal and electronic transport properties in order to function efficiently. These conditions can largely be achieved through careful design and synthesis of compounds that minimize thermal conductivity while allowing for good charge carrier transport, using techniques such as phonon-glass-electron-crystal, hierarchical nanostructuring, and energy filtering. While successful, these approaches often rely upon the use of sophisticated synthesis methodology and low abundance or toxic elements such as tellurium and lead that calls into question their use on a large scale. In order to address this concern, a completely new approach to synthesizing high efficiency thermoelectrics based on compositions of naturally occurring and earth abundant minerals has recently been realized. The family of compounds based on tetrahedrite, the most widespread sulfosalt mineral on Earth, can exhibit thermoelectric performance comparable to that of PbTe. These compounds, comprised predominantly of copper, zinc, and sulfur, display much interesting physics that is at the root of their favorable thermoelectric properties. Here we describe some of this physics that has been revealed through a combination of theoretical calculations, x-ray and neutron probes, and thermal and electronic characterization. Tetrahedrites offer the potential of a low-cost, environmentally benign material for use in thermoelectric power generators on a large scale. [Preview Abstract] |
Monday, March 2, 2015 12:27PM - 12:39PM |
B12.00005: Nanostructured YbAgCu$_{4}$ for potential cryogenic thermoelectric cooling Machhindra Koirala, Hui Wang, Mani Pokharel, Cyril Opeil, Zhifeng Ren We have studied thermoelectric properties of nanostructured YbAgCu$_{4}$ for cryogenic temperature range. Nanostructured YbAgCu$_{4}$ has been prepared using arc melting method followed by ball milling and hot pressing process. Thermal conductivity of the nanostructured samples has been reduced at 42 K by 30-50 {\%} compared to the previously reported value. A high power factor of 131 $\mu $W m$^{-1}$ K$^{-2}$ has been obtained at 22 K. A peak dimensionless figure of merit \textit{ZT} of 0.11 has been achieved at 42 K. With the variation of Cu-Ag composition, the temperature of peak \textit{ZT} can be tuned, which could be useful for the preparation of segmented legs. The method of nanostructuring can be implemented with different heavy fermions for obtaining high power factor with reduced thermal conductivity. [Preview Abstract] |
Monday, March 2, 2015 12:39PM - 12:51PM |
B12.00006: Atomic Disorder in Tetrahedrite John Robert Salasin, Bryan Chakoumakos, Claudia Rawn, Andrew May, Edgar Lara-Curzio, Michael McGuire, Huibo Cao Thermoelectrics (TE) are materials which turn heat energy into electrical energy with applications spanning multiple disciplines including space exploration, Peltier cooling, and engine efficiency. Tetrahedrite is a copper sulfosalt with the general formula Cu$_{\mathrm{12-x}}$M$_{\mathrm{x}}$(Sb,As)$_{\mathrm{4}}$S$_{\mathrm{13}}$. Where M denotes a Cu$^{\mathrm{2+}}$ site frequently replaced in natural tetrahedrite with Zn, Fe, Hg, or Mn. It has a cubic structure with an I-43m symmetry,$a=$10.4 {\AA}, and only a handful of adjustable parameters. This structural study corroborates theoretical calculations on atomic disorder. Positional disorder of the trigonally coordinated Cu(2) site is suggested from the temperature dependence of the atomic displacement parameters determine from single-crystal x-ray and neutron diffraction.\footnote{This research at ORNL's High Flux Isotope Reactor and Spallation Neutron Source was sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences, U.S. Department of Energy.} The displacements are extremely anisotropic for Cu(2) with a maximum rms static displacement of $\sim$ 0.25 {\AA}. [Preview Abstract] |
Monday, March 2, 2015 12:51PM - 1:03PM |
B12.00007: Exploring Materials Properties via Simulations and Experiments for Thermoelectricity Artem Khabibullin, Lilia Woods, George Nolas Thermoelectricity is an alternative route for energy conversion and suitable materials play an important role for enhanced efficiency of related applications. The optimization of the thermoelectric transport relies on the microscopic understanding of the materials internal properties, such as electronic structure characteristics. Simulations methods and effective medium theories are utilized to investigate advantageous features in materials composed of earth-abundant elements. Some general trends in the electronic structure influencing the transport are formulated for chalchogenide and clathrate systems suitable for thermoelectricity. We emphasize the importance of theoretical and computational efforts not only to identify existing classes, but also predict new structures with desirable internal characteristics for effective materials design and optimization. [Preview Abstract] |
Monday, March 2, 2015 1:03PM - 1:39PM |
B12.00008: Novel Thermoelectric Materials Synthesis and Thermodynamics Invited Speaker: Xinfeng Tang |
Monday, March 2, 2015 1:39PM - 1:51PM |
B12.00009: Ab Initio Electron Relaxation Times and Computational Screening of Thermoelectric Materials Boris Kozinsky, Georgy Samsonidze We report recent progress in development of an efficient approximation scheme for computing electron relaxation times in bulk crystalline materials from first principles. This technique takes into account electron-phonon coupling and opens up the possibility for ab initio calculations of electronic transport coefficients: electrical conductivity, the electronic part of thermal conductivity, and Seebeck coefficient. We find that electron relaxation times and transport coefficients are very sensitive to carrier concentration, and their accurate prediction is necessary for computational optimization of thermoelectric material composition. For a given thermoelectric material, we are able to determine the optimal carrier concentration which maximizes ZT at a target temperature. With this methodology at hand, systematic computational screening is performed in the compositional space of half-Heusler materials selected from materials databases and consisting of cheap earth-abundant elements. Good agreement is found with the available experimental data for previously synthesized half-Heusler compounds, and several new promising candidates for thermoelectric applications are identified, which have been synthesized and validated by experimental collaborators. Based on the results of our calculations, we also discuss the validity and applicability limits of the Wiedemann-Franz law for thermoelectric materials. [Preview Abstract] |
Monday, March 2, 2015 1:51PM - 2:03PM |
B12.00010: NMR study of Cu$_{2}$Se and Cu$_{1.98}$Ag$_{0.2}$Se superionic conductors Ali Sirusi Arvij, Joseph H. Ross, Jr., Sedat Ballikaya, Ctirad Uher Cu$_{2}$Se and Cu$_{1.98}$Ag$_{0.2}$Se are well known as superionic conductors and recently as thermoelectric materials due to observation of high ZT. We will report NMR of these compounds. Our results include indications of glassy anharmonic behavior at low temperatures, Cu ionic motion which becomes initiated near 90K, and motional narrowing near the phase transition at high temperatures as well as modified dynamics observed in the Ag-doped sample. NMR is particularly well suited to probe low frequency dynamics and at low temperatures the relaxation rate indicates anharmonic rattling behavior similar to what has been observed in other thermoelectric materials. A 90K change in the NMR spectra corresponds to the recently observed transport anomaly and indicates that the slow motion of Cu ions is initiated at this temperature and eventually becomes liquid-like at higher temperatures. We detect fast ionic motion in Cu$_{2}$Se starting at 140K whereas in the Ag-doped compound this onset shifts to a higher temperature around 300K. At high temperatures the spectra become motionally narrowed, and we will discuss the narrowing and shifts in terms of activated carrier density and ionic motion. [Preview Abstract] |
Monday, March 2, 2015 2:03PM - 2:15PM |
B12.00011: Mechanical robust BiSbTe alloys with superior thermoelectric performance:A case study of stable hierarchical nanostructured thermoelectric materials Xianli Su, Yun Zheng, Xinfeng Tang, Ctirad Uher Poor machinability and susceptibility to brittle fracture of commercial ingots often impose significant limitations on the manufacturing process and durability of thermoelectric devices. In this study, melt spinning combined with plasma activated sintering (MS-PAS) method is employed with commercial p-type zone-melted (ZM) ingots of Bi$_{0.5}$Sb$_{1.5}$Te$_{3}$. This fast synthesis approach achieves hierarchical structures and \textit{in-situ} nanoscale precipitates, resulting in the simultaneous improvement of thermoelectric performance and mechanical properties. Benefitting from a strong suppression of the lattice thermal conductivity, a peak \textit{ZT} of 1.22 is achieved at 340 K in MS-PAS synthesized structures, representing about a 40{\%} enhancement over that of ZM ingots. Moreover, MS-PAS specimens with hierarchical structures exhibit superior machinability and mechanical properties with an almost 30{\%} enhancement in the fracture toughness, eightfold and a factor of six increase in the compressive and flexural strength respectively. [Preview Abstract] |
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