High-pressure synthesis and thermoelectric performance of tellurium doped with bismuth
TL;DR: In this paper, low-toxic bismuth (Bi) was employed as dopant to optimize the thermoelectric performance of Te combining with a high-pressure synthesis method.
Abstract: Recently, it was found that element semiconductor tellurium (Te) has a high thermoelectric performance. However, it needs to be doped with high-toxic arsenic (As) to tune the carrier concentration of Te. In this paper, low-toxic bismuth (Bi) was employed as dopant to optimize the thermoelectric performance of Te combining with a high-pressure synthesis method. The effect of substituting Bi on the electrical transport and thermal transport properties of Te has been investigated. The results show that the solubility limit of Bi in Te is about 0.1 mol%. However, the trace amounts of Bi doping can tune the carrier concentration of Te effectively and thereby optimize its power factor. The thermal conductivity of non-doped Te prepared by high pressure is much lower than that of the sample prepared at ambient pressure. And Bi doping can further decrease the value due to the phonons scattered by the heavy impurity atom. An enhanced figure of merit ZT ~ 0.72 was obtained at 517 K, which is about four times that of non-doped Te and is comparable to the state-of-the-art thermoelectric alloys with more complex composition such as Bi2Te3 and PbTe.
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TL;DR: In this paper, the potential thermoelectric performance of hole-doped Bi2Se3, which is commonly considered to show inferior room temperature performance when compared to Bi2Te3, was analyzed.
Abstract: We present an analysis of the potential thermoelectric performance of hole-doped Bi2Se3, which is commonly considered to show inferior room temperature performance when compared to Bi2Te3. We find that if the lattice thermal conductivity can be reduced by nanostructuring techniques (as have been applied to Bi2Te3) the material may show optimized ZT values of unity or more in the 300 - 500 K temperature range and thus be suitable for cooling and moderate temperature waste heat recovery and thermoelectric solar cell applications. Central to this conclusion are the larger band gap and the relatively heavier valence bands of Bi2Se3.
47 citations
TL;DR: In this article, the grain size of Te0.94Se0.04As0.02 alloys was increased by increasing grain size to achieve an improvement in the TE performance.
Abstract: P-type elemental Te has exhibited a high thermoelectric (TE) figure of merit zT of ∼1.0 around 600 K, but its performance near room temperature is much deteriorated due to grain boundary scattering. In this work, the average zT of Te0.98As0.02 alloys is remarkably enhanced via increasing the grain size. Through increasing the grain size, the room temperature power factor is boosted from 0.44 × 10−3 W m−1 K−2 to 1.2 × 10−3 W m−1 K−2 due to the suppression of grain boundary scattering, while the lattice thermal conductivity remains unchanged, resulting in an ∼32% enhancement of device zT. The TE performance is further enhanced via Se alloying to reduce the lattice thermal conductivity. In the end, a high device zT of ∼0.64 at 600 K with a calculated conversion efficiency ∼8% is realized in the grain size-optimized Te0.94Se0.04As0.02 alloys, about 60% and 45% increments over that of the initial Te0.98As0.02 sample, respectively. The peak zT is maintained at ∼1.0 at 600 K. The strategy used here should be instructive for optimizing the TE properties of other materials with remarkable grain boundary scattering.
26 citations
TL;DR: The two types of nanorods were assembled into a 1D nanostructure, and with this structure, thermal conductivity decreased owing to the strong phonon scattering effect, and this nanorod composite had a dramatically improved ZT value.
Abstract: In this study, Te/Cu2Te nanorod composites were synthesized using various properties of Cu2Te, and their thermoelectric properties were investigated. The nanorods were synthesized through a solution phase mixing process, using polyvinylpyrrolidone (PVP). With increasing Cu2Te content, the composites exhibited a reduced Seebeck coefficient and enhanced electrical conductivity. These characteristic changes were due to the high electrical conductivity and low Seebeck coefficient of Cu2Te. The composite containing 30 wt.% of Cu2Te nanorods showed the maximum power factor (524.6 μV/K at room temperature). The two types of nanorods were assembled into a 1D nanostructure, and with this structure, thermal conductivity decreased owing to the strong phonon scattering effect. This nanorod composite had a dramatically improved ZT value of 0.3, which was ~545 times larger than that of pristine Te nanorods.
26 citations
TL;DR: In this paper, two types of MWCNT/Te nanostructure composites with two different types of Te particles (powder and nanorods) and various mWCNT contents were synthesized and their thermoelectric properties were analyzed.
18 citations
TL;DR: In this paper, high pressure was employed to synthesize and modulate the electrical transport properties of (Bi,Sb)2Te3 alloys, and the texture and microstructure were improved with high pressure.
Abstract: High pressure as an effective strategy was employed to synthesize and modulate the electrical transport properties of (Bi,Sb)2Te3 alloys. Intrinsic point defects could be significantly regulated via high pressure, inducing a suitable donor-like effect to optimize the carrier concentration. The texture and microstructure were improved with high pressure, and a nanograin with (00l) orientation was observed in the (Bi,Sb)2Te3 matrix, suggesting that high pressure could facilitate the recrystallization of lattice defects along the (00l) orientation. Based on the synergistic effect of high pressure on intrinsic point defects, texture, and microstructure, the carrier concentration and mobility are regularly modulated, resulting in the room-temperature power factor of the (Bi,Sb)2Te3 alloys exhibiting a strong correlation with pressure. Hence, these important results here provide a prospective strategy in the improvement in the electrical transport properties of the Bi2Te3-based alloys according to the rational design of intrinsic point defects, texture, and microstructure with high pressure.
13 citations
References
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14 Jul 1995
TL;DR: In this article, Rowe et al. proposed a method for reducing the thermal conductivity of a thermoelectric generator by reducing the carrier concentration of the generator, which was shown to improve the generator's performance.
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
4,192 citations
TL;DR: A successful implementation through the use of the thallium impurity levels in lead telluride (PbTe) is reported, which results in a doubling of zT in p-type PbTe to above 1.5 at 773 kelvin.
Abstract: The efficiency of thermoelectric energy converters is limited by the material thermoelectric figure of merit (zT). The recent advances in zT based on nanostructures limiting the phonon heat conduction is nearing a fundamental limit: The thermal conductivity cannot be reduced below the amorphous limit. We explored enhancing the Seebeck coefficient through a distortion of the electronic density of states and report a successful implementation through the use of the thallium impurity levels in lead telluride (PbTe). Such band structure engineering results in a doubling of zT in p-type PbTe to above 1.5 at 773 kelvin. Use of this new physical principle in conjunction with nanostructuring to lower the thermal conductivity could further enhance zT and enable more widespread use of thermoelectric systems.
3,401 citations
"High-pressure synthesis and thermoe..." refers background in this paper
...71 @ 700 K) [23] if only considering the doping effect....
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TL;DR: In this article, a first order correction to the degenerate limit of L can be found based on the measured thermopower, |S|, independent of temperature or doping.
Abstract: In analyzing zT improvements due to lattice thermal conductivity (κ_L ) reduction, electrical conductivity (σ) and total thermal conductivity (κ_(Total)) are often used to estimate the electronic component of the thermal conductivity (κ_E) and in turn κ_L from κ_L = ∼ κ_(Total) − LσT. The Wiedemann-Franz law, κ_E = LσT, where L is Lorenz number, is widely used to estimate κ_E from σ measurements. It is a common practice to treat L as a universal factor with 2.44 × 10^(−8) WΩK^(−2) (degenerate limit). However, significant deviations from the degenerate limit (approximately 40% or more for Kane bands) are known to occur for non-degenerate semiconductors where L converges to 1.5 × 10^(−8) WΩK^(−2) for acoustic phonon scattering. The decrease in L is correlated with an increase in thermopower (absolute value of Seebeck coefficient (S)). Thus, a first order correction to the degenerate limit of L can be based on the measured thermopower, |S|, independent of temperature or doping. We propose the equation: L=1.5+exp[−_(|S|)_(116)] (where L is in 10^(−8) WΩK^(−2) and S in μV/K) as a satisfactory approximation for L. This equation is accurate within 5% for single parabolic band/acoustic phonon scattering assumption and within 20% for PbSe, PbS, PbTe, Si_(0.8) Ge _(0.2) where more complexity is introduced, such as non-parabolic Kane bands, multiple bands, and/or alternate scattering mechanisms. The use of this equation for L rather than a constant value (when detailed band structure and scattering mechanism is not known) will significantly improve the estimation of lattice thermal conductivity.
1,147 citations
"High-pressure synthesis and thermoe..." refers background in this paper
...5 ? exp [-|S|/116] in this study, which was proposed by Snyder [20]....
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...The Lorenz number is estimated by the equation L = 1.5 ? exp [-|S|/116] in this study, which was proposed by Snyder [20]....
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TL;DR: In this article, it was shown that the Seebeck coefficient of a semiconductor has a maximum value that is close to one-half the energy gap divided by eT, with account taken of the mobility and effective mass ratios.
Abstract: It is shown that the magnitude of the Seebeck coefficient of a semiconductor has a maximum value that is close to one-half the energy gap divided by eT. An expression for the position of the Fermi level at which the Seebeck coefficient has a maximum or minimum value is derived, with account taken of the mobility and effective mass ratios. It is concluded that measurement of the Seebeck coefficient as a function of temperature on any novel semiconductor is one of the simplest ways of estimating its band gap.
659 citations
"High-pressure synthesis and thermoe..." refers background or methods in this paper
...The band gap of Te is evaluated by the Goldsmid–Sharp formula [15], which is given in the ‘‘Seebeck coefficient’’ part....
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...The effective Eg can be estimated by the Goldsmid–Sharp formula [15]:...
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TL;DR: Here it is shown that a simple elemental semiconductor, tellurium, exhibits a high thermoelectric figure of merit of unity, not only demonstrating the concept but also filling up the high performance gap from 300 to 700 K for elemental thermoeLECTrics.
Abstract: Good thermoelectric materials are often complex compounds. Here, the authors reveal that elemental tellurium has a high thermoelectric figure of merit between 300 and 700 K when doped with As, with the potential advantages of easy preparation and relative isotropy.
353 citations
"High-pressure synthesis and thermoe..." refers background in this paper
...performance at 600 K due to its nested valence bands [4]....
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