Journal Article

# Porous bismuth antimony telluride alloys with excellent thermoelectric and mechanical properties

02 Mar 2021-Journal of Materials Chemistry (The Royal Society of Chemistry)-Vol. 9, Iss: 8, pp 4990-4999
Abstract: p-Type BiSbTe alloys possess the highest ZT near room temperature, but inferior mechanical properties due to the atomically layered structure with weak van der Waals interactions. Here we report the successful preparation of porous BiSbTe alloys by sequential high-pressure synthesis, ball milling, and spark plasma sintering. Porosity usually has a negative effect on the material's mechanical properties. However, both thermoelectric and mechanical properties of our porous bulks are greatly enhanced, which benefit from the unique microstructure featuring closely bonded equiaxed grains and uniformly distributed pores (with a porosity of ca. 0.15). The optimal Bi0.42Sb1.58Te3 shows a maximum ZT of 1.27 around 350 K and an average ZT of 1.15 in the measured temperature range of 298–463 K. Furthermore, excellent mechanical properties including hardness, bending and compressive strengths are achieved in these porous samples, which are competitive with (or even better than) those of dense samples. The current structural architecture strategy can promote the development of porous thermoelectric materials, especially materials with similar anisotropic crystal structures.

Topics: , , Antimony telluride (54%) ... read more
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Open accessJournal Article
01 Oct 2021-Nanomaterials
Abstract: Engineering materials to include nanoscale porosity or other nanoscale structures has become a well-established strategy for enhancing the thermoelectric performance of dielectrics. However, the approach is only considered beneficial for materials where the intrinsic phonon mean-free path is much longer than that of the charge carriers. As such, the approach would not be expected to provide significant performance gains in polycrystalline semiconducting alloys, such as SixGe1-x, where mass disorder and grains provide strong phonon scattering. In this manuscript, we demonstrate that the addition of nanoscale porosity to even ultrafine-grained Si0.8Ge0.2 may be worthwhile. The semiclassical Boltzmann transport equation was used to model electrical and phonon transport in polycrystalline Si0.8Ge0.2 containing prismatic pores perpendicular to the transport current. The models are free of tuning parameters and were validated against experimental data. The models reveal that a combination of pores and grain boundaries suppresses phonon conductivity to a magnitude comparable with the electronic thermal conductivity. In this regime, ZT can be further enhanced by reducing carrier concentration to the electrical and electronic thermal conductivity and simultaneously increasing thermopower. Although increases in ZT are modest, the optimal carrier concentration is significantly lowered, meaning semiconductors need not be so strongly supersaturated with dopants.

Topics: Thermal conductivity (54%), Phonon scattering (53%),  ... read more

2 Citations

Open accessPosted Content
Abstract: Engineering materials to include nanoscale porosity or other nanoscale structures has become a well-established strategy for enhancing the thermoelectric performance of dielectrics. However, the approach is only considered beneficial for materials where the intrinsic phonon mean free path is much longer than that of the charge carriers. As such, the approach would not be expected to provide significant performance gains in polycrystalline semiconducting alloys such as $\mathrm{Si_xGe_{1-x}}$, where mass disorder and grains provide strong phonon scattering. In this manuscript, we demonstrate that the addition of nanoscale porosity to even ultrafine-grained $\mathrm{Si_{0.8}Ge_{0.2}}$ may be worthwhile. The semiclassical Boltzmann transport equation was used to model electrical and phonon transport in polycrystalline $\mathrm{Si_{0.8}Ge_{0.2}}$ containing prismatic pores perpendicular to the transport current. The models are free of tuning parameters and were validated against experimental data. The models reveal that a combination of pores and grain boundaries suppresses phonon conductivity to a magnitude comparable with the electronic thermal conductivity. In this regime, $ZT$ can be further enhanced by reducing carrier concentration to the electrical and electronic thermal conductivity and simultaneously increasing thermopower. Although increases in $ZT$ are modest, the optimal carrier concentration is significantly lowered, meaning semiconductors need not be so strongly supersaturated with dopants.

Topics: Phonon scattering (55%), Seebeck coefficient (52%), Thermal conductivity (52%) ... read more

Open accessJournal Article
Shao-Ji Huang1, Tian-Ran Wei1, Heyang Chen1, Jie Xiao2  +4 moreInstitutions (2)
Abstract: Ag2Se is a narrow band gap n-type semiconductor with high carrier mobility and low lattice thermal conductivity. It has high thermoelectric performance near room temperature. However, there is a noticeable data discrepancy for thermoelectric performance in the reported literature studies, which greatly hinders the rational understanding and potential application of this material. In this work, we comprehensively studied the homogeneity, reproducibility, and thermal stability of bulk Ag2Se prepared by melting and mechanical alloying methods followed by spark plasma sintering. By virtue of the atom probe topology technique, we revealed nanosized Ag- or Se-rich precipitates and micropores with Se-aggregated interfaces that have not been detected previously. The samples prepared by melting and spark plasma sintering exhibit the best homogeneity and repeatability in thermoelectric properties despite abundant nanoprecipitates. Moreover, the thermoelectric performance of Ag2Se is greatly improved by introducing a slight amount of excess selenium. The average zT can steadily reach 0.8-0.9 in the range of 300-380 K, which is among the highest values reported for Ag2Se-based materials. This work will rationalize the evaluation of the thermoelectric performance of Ag2Se.

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Open accessJournal Article
Hengyi Wu1, Suiting Ning1, N. Qi1, Feng Ren1  +3 moreInstitutions (2)
Abstract: Due to the ultrawide bandgap (4.9 eV), high carrier mobility (300 cm2V−1s−1), and high thermal stability, β−Ga2O3 can be a potential candidate for high-temperature thermoelectric materials. However, the intrinsically high thermal conductivity may hinder its application for thermoelectric conversion. In this work, porous β−Ga2O3 was prepared by the solvothermal method together with spark plasma sintering technology. Positron lifetime measurement and N2 adsorption confirm the introduction of pores by adding sucrose in the sample preparation. The sucrose-derived β−Ga2O3 sintered at a relatively low temperature of 600 °C remains highly porous, which results in an extremely low thermal conductivity of 0.45 W m−1K−1 at room temperature, and it further decreases to 0.29 W m−1K−1 at 600 °C. This is the lowest thermal conductivity for β−Ga2O3 reported so far. Our work provides an avenue to reduce the thermal conductivity for β−Ga2O3 and is believed to be widely applicable to many other thermoelectric materials.

Topics: , Thermal conductivity (56%),  ... read more

Journal Article
Deyu Bao1, Qiang Sun2, Linsen Huang1, Jie Chen1  +6 moreInstitutions (3)
Abstract: Tremendous efforts have been focusing on the improvement of p-type (Bi, Sb)2Te3-based thermoelectric materials for commercial applications. In this study, we achieve versatile interface engineering through a surface decoration of Bi0.5Sb1.5Te3 by amorphous Sb2S3 combining with spark plasma sintering, which introduces semi-coherent Sb/Bi0.5Sb1.5Te3 interfaces and dopes S into Bi0.5Sb1.5Te3. Semi-coherent Sb/Bi0.5Sb1.5Te3 interfaces strongly scatter phonons and lower energy carriers, leading to decreased thermal conductivity and increased Seebeck coefficient, while the electrical conductivity is not sacrificed due to the compromise of the slightly reduced carrier mobility by interfacial scattering and the increased carrier concentration by S doping. Benefited from the decoupled thermoelectric properties, a significantly enhanced power factor of 3345.40 μW m−1 K−2 and a low thermal conductivity of 0.78 W m−1 K−1 is obtained in Bi0.5Sb1.5Te3-0.4%Sb2S3, leading to a high peak zT of ∼ 1.31 at 330 K, which shows a 54% enhancement compared with pristine Bi0.5Sb1.5Te3. Moreover, a conversion efficiency of ∼ 7.6% can be predicted in a single leg Bi0.5Sb1.5Te3-0.4%Sb2S3-based module under a cold side temperature of 300 K and hot side temperature of 480 K. This study paves a facile amorphous Sb2S3 induced interface engineering strategy for the development of high performance (Bi,Sb)2Te3-based thermoelectric materials.

Topics: , , Seebeck coefficient (59%) ... read more
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61 results found

Journal Article
01 Sep 1951-
Abstract: An attempt is made here to explain the observed phenomena in the yielding and ageing of mild steel, described in two previous papers, in the general terms of a grain-boundary theory. On this hypothesis, a satisfactory explanation of the variation of the lower yield point with grain size may be developed. It is shown that strain-ageing must involve two processes: a healing of the grain-boundary films, coupled with a hardening in the grains themselves. A discussion of the possible nature of the grain-boundary film is also undertaken.

5,036 Citations

Journal Article
Bed Poudel1, Qing Hao2, Yi Ma1, Yucheng Lan1  +11 moreInstitutions (3)
02 May 2008-Science
Abstract: The dimensionless thermoelectric figure of merit (ZT) in bismuth antimony telluride (BiSbTe) bulk alloys has remained around 1 for more than 50 years. We show that a peak ZT of 1.4 at 100°C can be achieved in a p-type nanocrystalline BiSbTe bulk alloy. These nanocrystalline bulk materials were made by hot pressing nanopowders that were ball-milled from crystalline ingots under inert conditions. Electrical transport measurements, coupled with microstructure studies and modeling, show that the ZT improvement is the result of low thermal conductivity caused by the increased phonon scattering by grain boundaries and defects. More importantly, ZT is about 1.2 at room temperature and 0.8 at 250°C, which makes these materials useful for cooling and power generation. Cooling devices that use these materials have produced high-temperature differences of 86°, 106°, and 119°C with hot-side temperatures set at 50°, 100°, and 150°C, respectively. This discovery sets the stage for use of a new nanocomposite approach in developing high-performance low-cost bulk thermoelectric materials.

Topics: Bismuth telluride (63%), , Antimony telluride (61%) ... read more

4,218 Citations

Book
14 Jul 1995-
Abstract: Introduction, D.M. Rowe General Principles and Theoretical Considerations Thermoelectric Phenomena, D.D. Pollock Coversion Efficiency and Figure-of-Merit, H.J. Goldsmid Thermoelectric Transport Theory, C.M. Bhandari Optimization of Carrier Concentration, C.M. Bhandari and D.M. Rowe Minimizing the Thermal Conductivity, C.M. Bhandari Selective Carrier Scattering in Thermoelectric Materials, Y.I. Ravich Thermomagnetic Phenomena, H.J. Goldsmid Material Preparation Preparation of Thermoelectric Materials from Melts, A. Borshchevsky Powder Metallurgy Techniques, A.N. Scoville PIES Method of Preparing Bismuth Alloys, T. Ohta and T. Kajikawa Preparation of Thermoelectric Materials by Mechanical Alloying, B.A. Cook, J.L. Harringa, and S.H. Han Preparation of Thermoelectric Films, K. Matsubara, T. Koyanagi, K. Nagao, and K. Kishimoto Measurement of Thermoelectric Properties Calculation of Peltier Device Performance, R.J. Buist Measurements of Electrical Properties, I.A. Nishida Measurement of Thermal Properties, R. Taylor Z-Meters, H.H. Woodbury, L.M. Levinson, and S. Lewandowski Methodology for Testing Thermoelectric Materials and Devices, R.J. Buist Thermoelectric Materials Bismuth Telluride, Antimony Telluride, and Their Solid Solutions, H. Scherrer and S. Scherrer Valence Band Structure and the Thermoelectric Figure-of-Merit of (Bi1-xSbx)Te3 Crystals, M. Stordeur Lead Telluride and Its Alloys, V. Fano Properties of the General Tags System, E.A. Skrabek and D.S. Trimmer Thermoelectric Properties of Silicides, C.B. Vining Polycrystalline Iron Disilicide as a Thermoelectric Generator Material, U. Birkholz, E. Gross, and U. Stohrer Thermoelectric Properties of Anisotropic MnSi1.75 , V.K. Zaitsev Low Carrier Mobility Materials for Thermoelectric Applications, V.K. Zaitsev, S.A. Ktitorov, and M.I. Federov Semimetals as Materials for Thermoelectric Generators, M.I. Fedorov and V.K. Zaitsev Silicon Germanium, C.B. Vining Rare Earth Compounds, B.J. Beaudry and K.A. Gschneidner, Jr. Thermoelectric Properties of High-Temperature Superconductors, M. Cassart and J.-P. Issi Boron Carbides, T.L. Aselage and D. Emin Thermoelectric Properties of Metallic Materials, A.T. Burkov and M.V. Vedernikov Neutron Irradiation Damage in SiGe Alloys, J.W. Vandersande New Materials and Performance Limits for Thermoelectric Cooling, G.A. Slack Thermoelectric Generation Miniature Semiconductor Thermoelectric Devices, D.M. Rowe Commercially Available Generators, A.G. McNaughton Modular RTG Technology, R.F. Hartman Peltier Devices as Generators, G. Min and D.M. Rowe Calculations of Generator Performance, M.H. Cobble Generator Applications Terrestrial Applications of Thermoelectric Generators, W.C. Hall Space Applications, G.L. Bennett SP-100 Space Subsystems, J.F. Mondt Safety Aspects of Thermoelectrics in Space, G.L. Bennett Low-Temperature Heat Conversion, K. Matsuura and D.M. Rowe Thermoelectric Refrigeration Introduction, H.J. Goldsmid Module Design and Fabrication, R. Marlow and E. Burke Cooling Thermoelements with Superconducting Leg, M.V. Vedernikov and V.L. Kuznetsov Applications of Thermoelectric Cooling Introduction, H.J. Goldsmid Commercial Peltier Modules, K.-I. Uemura Thermoelectrically Cooled Radiation Detectors, L.I. Anatychuk Reliability of Peltier Coolers in Fiber-Optic Laser Packages, R.M. Redstall and R. Studd Laboratory Equipment, K.-I. Uemura Large-Scale Cooling: Integrated Thermoelectric Element Technology, J.G. Stockholm Medium-Scale Cooling: Thermoelectric Module Technology, J.G. Stockholm Modeling of Thermoelectric Cooling Systems, J.G. Stockholm

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4,111 Citations

Journal Article
Kanishka Biswas1, Jiaqing He1, Ivan Blum2, Ivan Blum1  +7 moreInstitutions (5)
20 Sep 2012-Nature
Abstract: Controlling the structure of thermoelectric materials on all length scales (atomic, nanoscale and mesoscale) relevant for phonon scattering makes it possible to increase the dimensionless figure of merit to more than two, which could allow for the recovery of a significant fraction of waste heat with which to produce electricity.