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Showing papers on "Thermoelectric effect published in 2006"


Journal ArticleDOI
TL;DR: In this article, the complex Zintl compound, Yb14MnSb11, was proposed for high-temperature (>900 K), p-type materials development for thermoelectric power generation.
Abstract: Thermoelectric materials provide a key solution to energy problems through the conversion of heat into electrical energy. We report that the complex Zintl compound, Yb14MnSb11, breaks a 2-decade stagnation in high-temperature (>900 K), p-type materials development for thermoelectric power generation. This material achieves quadrupled efficiency and virtually doubled figure of merit over the current state-of-the-art, SiGe, thus earmarking it superior for thermoelectric applications in segmented devices. Yb14MnSb11 represents the first complex Zintl phase with substantially higher figure of merit and efficiency than any other competing materials, opening a new class of thermoelectric compounds with remarkable chemical and physical properties.

698 citations


Journal ArticleDOI
TL;DR: In this paper, a review of thermoelectric energy-conversion technology for radioisotope space power systems and several proposed applications of thermal waste-heat recovery devices in the automotive industry is presented.
Abstract: Historically, thermoelectric technology has only occupied niche areas, such as the radioisotope thermoelectric generators for NASA’s spacecrafts, where the low cooling coefficient of performance (COP) and energy-conversion efficiency are outweighed by the application requirements.Recent materials advances and an increasing awareness of energy and environmental conservation issues have rekindled prospects for automotive and other applications of thermoelectric materials.This article reviews thermoelectric energy-conversion technology for radioisotope space power systems and several proposed applications of thermoelectric waste-heat recovery devices in the automotive industry.

540 citations


Journal ArticleDOI
TL;DR: In this article, the authors look at various classes of materials to understand their behavior and determine methods to modify or tune them to optimize their thermoelectric properties, such as the use of rattlers in cage structures such as skutterudites, or mixed-lattice atoms such as complex half-Heusler alloys.
Abstract: Good thermoelectric materials possess low thermal conductivity while maximizing electric carrier transport. This article looks at various classes of materials to understand their behavior and determine methods to modify or “tune” them to optimize their thermoelectric properties. Whether it is the use of “rattlers” in cage structures such as skutterudites, or mixed-lattice atoms such as the complex half-Heusler alloys, the ability to manipulate the thermal conductivity of a material is essential in optimizing its properties for thermoelectric applications.

435 citations


Journal ArticleDOI
TL;DR: The k-space structure of the lowest conduction band of LiZnSb is analyzed in detail, and excellent thermoelectric properties are expected for this material.
Abstract: An automated band structure calculation based on the inorganic crystal structure database and the augmented plane wave method for electronic structure calculations is presented. Using a rigid band approach and semiclassic Boltzmann theory the band structures are analyzed and a large number of compounds are screened for potential interesting thermoelectric properties. We thereby propose LiZnSb as a potential new thermoelectric material. The k-space structure of the lowest conduction band of LiZnSb is analyzed in detail, and excellent thermoelectric properties are expected for this material. Furthermore the lattice dynamics are calculated, and anisotropic lattice thermal conduction is predicted.

416 citations


Journal ArticleDOI
TL;DR: In this article, the Czochralski method was used to grow a 46mm-long crystal of the Ba8Ga16Ge30 clathrate, which was cut into disks that were evaluated for thermoelectric performance.
Abstract: The Czochralski method was used to grow a 46-mm-long crystal of the Ba8Ga16Ge30 clathrate, which was cut into disks that were evaluated for thermoelectric performance. The Seebeck coefficient and electrical and thermal conductivities all showed evidence of a transition from extrinsic to intrinsic behavior in the range of 600–900K. The corresponding figure of merit (ZT) was found to be a record high of 1.35 at 900K and with an extrapolated maximum of 1.63 at 1100K. This makes the Ba8Ga16Ge30 clathrate an exceptionally strong candidate for medium and high-temperature thermoelectric applications.

401 citations


Journal ArticleDOI
TL;DR: A finite-temperature formula for the orbital magnetization is derived, which enables to provide an explicit expression for the off-diagonal thermoelectric conductivity, to establish the Mott relation between the anomalous Nernst and Hall effects, and to reaffirm the Onsager relations between reciprocal thermoelectedric conductivities.
Abstract: We develop a theory of the Berry-phase effect in anomalous transport in ferromagnets driven by statistical forces such as the gradient of temperature or chemical potential. Here a charge Hall current arises from the Berry-phase correction to the orbital magnetization rather than from the anomalous velocity, which does not exist in the absence of a mechanical force. A finite-temperature formula for the orbital magnetization is derived, which enables us to provide an explicit expression for the off-diagonal thermoelectric conductivity, to establish the Mott relation between the anomalous Nernst and Hall effects, and to reaffirm the Onsager relations between reciprocal thermoelectric conductivities. A first-principles evaluation of our expression is carried out for the material ${\mathrm{CuCr}}_{2}{\mathrm{Se}}_{4\ensuremath{-}x}{\mathrm{Br}}_{x}$, obtaining quantitative agreement with a recent experiment.

399 citations


Journal ArticleDOI
TL;DR: It is reported that the Ag-free system Na1 xPbmSbyTem+2, with appropriate combinations of m, y, and x, achieves record-high ZT values for a p-type bulk thermoelectric material, and shows that the high performance of these materials derives mainly from a low thermal conductivity.
Abstract: Thermoelectric materials are special types of semiconductors that function as “heat pumps” and as heat-to-electricity converters. Thermoelectric power generation allows for small size, high reliability, and quiet operation. Efficient thermoelectric-based heat-to-electricity converters require higher performance materials than are currently available. Direct conversion of heat to electricity could be achieved with solidstate devices based on thermoelectric materials. These devices could play an important role in future energy production, conversion, management, and utilization. When a temperature gradient is created across a thermoelectric module, a voltage is generated, owing to the Seebeck effect. This voltage can be used to drive an external load. Currently, there is a strong scientific and technological drive to identify new materials with enhanced thermoelectric figures of merit ZT= (sS/k)T (where s is the electrical conductivity, S the thermopower or Seebeck coefficient, k the thermal conductivity, and T the temperature). The numerator sS is called the power factor PF. Several classes of materials are currently under investigation, including complex chalcogenides, doped PbTe and its solid solutions, such as Pb1 xSnxTe, [5,6] superlattice thin films, and quantum-dot superlattices. Also of interest are skutterudites, metal oxides, and intermetallic clathrates. The superlattice thin-film structures of Bi2Te3/Sb2Te3 grown from chemical vapor deposition, and of PbSe0.98Te0.02/PbTe formed by molecular beam epitaxy (MBE) have figures of merit greater than ZT= 2 (at approximately 300 and 550 K, respectively). The MBE-grown thin films PbSe0.98Te0.02/PbTe are n-type materials and contain pyramid-shaped “nanodots” of PbSe of uniform size (approximately 20 nm), which form spontaneously inside a matrix of PbTe. Because energyconversion applications require materials in large quantities, we seek bulk analogues of these systems with similar figures of merit. A recent contribution to these efforts was the discovery of the n-type Ag-based tellurides AgSbTe2/PbTe, which can exhibit high figures of merit (ZT 1.7 at 700 K) when properly doped. To construct a fully functioning optimal thermoelectric device, both nand p-type materials are needed. To date, there is no p-type counterpart to AgSbTe2/ PbTe with similar performance. The highest figure of merit reported for p-type bulk materials (ZT 1.2 at 700 K) is exhibited by the so-called TAGS system (based on Te, Ag, Ge, and Sb: (GeTe)1 x((Ag2Te)1 y(Sb2Te3)y)x). [23] These Ge-containing materials, though more efficient than PbTe, have found limited use, owing to their high cost and to a lowtemperature phase transition. Recently, we described the ptype materials Ag(Pb1 ySny)mSbTe2+m, which show outstanding thermoelectric properties, reaching a maximum figure of merit of ZT 1.45 at 630 K. Herein, we report that the Ag-free system Na1 xPbmSbyTem+2, with appropriate combinations of m, y, and x, achieves record-high ZT values for a p-type bulk thermoelectric material. The effect of the composition on the thermoelectric properties is profound. We show that the high performance of these materials derives mainly from a low thermal conductivity. High-resolution transmission electron microscopy (HRTEM) demonstrates pervasive nanostructuring in Na1 xPbmSbyTem+2, which may be the root cause for the remarkably low thermal conductivity. The Na1 xPbmSbyTem+2 system was selected for study because it should be naturally prone to create Na,Sb-rich clusters in the lattice. The distribution of Na and Sb ions in the Pb sublattice cannot be random, as would be demanded by a solid solution, because Coulombic forces alone tend to drive the system to clustering at the nanoscale, thereby lowering the overall energy. The results described herein are in agreement with long-standing theoretical predictions that nanostructuring in semiconductors would lead to enhanced thermoelectric figures of merit. The Na1 xPbmSbyTem+2 materials could find applications in devices for power generation from a wide variety of hot sources, for example, vehicle exhausts, coal-burning installations, or electric power utilities. Na1 xPbmSbyTem+2 (y 1) samples (see Supporting Information for synthesis details) exhibit p-type conduction from 300 to 700 K. Ingots with the composition Na0.95Pb19SbTe21 (m= 19, x= 0.05, y= 1) exhibit an electrical conductivity of s= 1422 Scm 1 with a positive thermopower of S= 105 mVK 1 at room temperature. This leads to the relatively high power factor of PF= 15.6 mWcm K . The temperature dependence of the electrical conductivity and the thermopower of Na0.95Pb19SbTe21 are shown in Figure 1A. The conductivity decreases with increasing temperature, which is consistent with degenerate semiconductors, and reaches s= 150 Scm 1 at 700 K. However, the thermopower increases rapidly to S= 357.6 mVK 1 at 700 K, yielding a much higher power factor of PF= 19 mWcm K . For samples of composition Na0.95Pb20SbTe22 (m= 20, x= 0.05, y= 1), an electrical conductivity of s= 1541 Scm 1 and a [*] Dr. P. F. P. Poudeu, Prof. M. G. Kanatzidis Department of Chemistry Michigan State University East Lansing, MI 48824 (USA) Fax: (+1)517-353-1793 E-mail: kanatzid@cem.msu.edu

375 citations


Journal ArticleDOI
TL;DR: In this article, the role of spin entropy contributions to thermopower was presented, in connection with strong electron correlation and triangular lattices, and it was found that good junctions can be formed using Ag paste including p- and n-type oxide powders.
Abstract: Layered CoO2 materials are excellent candidates for potential thermoelectric applications. Their single crystals show good p-type thermoelectric properties at temperatures higher than 800K in air.Recently, the mechanism of thermoelectric properties was clarified through a discussion of electronic and crystallographic structure. In order to fabricate thermoelectric modules possessing good power-generation properties, thermoelectric materials and metallic electrodes must be connected with low contact resistance and high mechanical strength.It has been found that good junctions can be formed using Ag paste including p- and n-type oxide powders.The role of spin entropy contributions to thermopower will be presented, in connection with strong electron correlation and triangular lattices.

327 citations


Journal ArticleDOI
TL;DR: The conducting layered cobaltate NaxCoO2 exhibits several interesting electronic phases as the Na content x is varied, including water-induced superconductivity4 and an insulating state that is destroyed by field5.
Abstract: Research on the oxide perovskites has uncovered electronic properties that are strikingly enhanced compared with those in conventional metals. Examples are the high critical temperatures of the cuprate superconductors and the colossal magnetoresistance in the manganites. The conducting layered cobaltate Na(x)CoO2 exhibits several interesting electronic phases as the Na content x is varied, including water-induced superconductivity and an insulating state that is destroyed by field. Initial measurements showed that, in the as-grown composition, Na(x)CoO2 has moderately large thermopower S and conductivity sigma. However, the prospects for thermoelectric cooling applications faded when the figure of merit Z was found to be small at this composition (0.6 0.75, S undergoes an even steeper enhancement. At the critical doping x(p) approximately 0.85, Z (at 80 K) reaches values approximately 40 times larger than in the as-grown crystals. We discuss prospects for low-temperature thermoelectric applications.

257 citations


Journal ArticleDOI
TL;DR: In this paper, a range of materials used in superlattice form to improve the thermoelectric figure of merit is discussed. But the authors focus on a range only on the materials used to improve electron transport and not on the lattice mismatch and potential differences at the interfaces.
Abstract: Superlattices consist of alternating thin layers of different materials stacked periodically.The lattice mismatch and electronic potential differences at the interfaces and resulting phononand electron interface scattering and band structure modifications can be exploited to reduce phonon heat conduction while maintaining or enhancing the electron transport.This article focuses on a range of materials used in superlattice form to improve the thermoelectric figure of merit.

246 citations


Journal ArticleDOI
TL;DR: In this paper, the authors examined the thermally stable MNiSn (M=Ti, Zr, Hf) half-Heusler phases, as n-type thermoelectric materials, for high-temperature power generation.
Abstract: The merit of thermally stable MNiSn (M=Ti, Zr, Hf) half-Heusler phases, as n-type thermoelectric materials, for high-temperature power generation has been examined. Sb doping at the Sn site is shown to increase both the figure of merit, ZT, and the temperature at which ZT is maximized. The benefits of increased alloying at the M and Ni sites, on the thermal conductivity and thermoelectric transport properties, have also been investigated. The thermoelectric figure of merit, ZT∼0.8 at T∼800°C, for select Sb-doped MNiSn alloys was found to meet or exceed the industry benchmark set by SiGe alloys.

Journal ArticleDOI
TL;DR: In this paper, the authors investigated the thermoelectric properties of polycrystalline samples Ca1−xAxMnO3 (A=Yb, Tb, Nd, and Ho) and showed that the thermal conductivity is mainly driven by the atomic weight of the A site and decreases with it.
Abstract: CaMnO3 is an electron-doped compound which belongs to the perovskite family. Despite its high Seebeck coefficient S value, the figure of merit at high temperature remains low due to its large resistivity ρ(ρ300K=2Ωcm). To optimize the performance of this material in terms of thermoelectric properties, several substitutions have been attempted on the Ca site to decrease the ρ. Structure and thermoelectric properties of polycrystalline samples Ca1−xAxMnO3 (A=Yb, Tb, Nd, and Ho) have been investigated. Although ρ strongly depends on the ionic radius ⟨rA⟩ and carrier concentration, we have shown that the thermal conductivity κ is mainly driven by the atomic weight of the A site and decreases with it. Therefore, it seems that the S, ρ, and κ could be controlled separately. For instance, the highest dimensionless ZT (=0.16) has been obtained at 1000K in the air for Ca0.9Yb0.1MnO3.

Journal ArticleDOI
TL;DR: In this paper, a coiled-up thermoelectric micro power generator is presented using metal films sputtered on a thin polyimide foil, which yields higher voltages at a smaller generator area.
Abstract: A coiled-up thermoelectric micro power generator is presented using metal films sputtered on a thin polyimide foil. The principle of coiling-up yields higher voltages at a smaller generator area. Design optimizations were made for maximum long-term power output using the human body as heat source. It is shown that for low-power electronics like a wrist-watch even simple materials are sufficient and allow lowest-cost production, e.g. screen printing. Thermoelectrical screen-printing pastes were developed and results of first screen printed thermocouples are given.

Journal ArticleDOI
TL;DR: In this paper, structural, electrical, and thermal transport properties of CoSb3 partially filled with indium are reported, where polycrystalline samples of InxCo4Sb12 (0 ≤ x ≤ 0.3) were prepared by solid-state reaction under a gas mixture of 5% H2 and 95% Ar.
Abstract: Structural, electrical, and thermal transport properties of CoSb3 partially filled with indium are reported. Polycrystalline samples of InxCo4Sb12 (0 ≤ x ≤ 0.3) were prepared by solid-state reaction under a gas mixture of 5% H2 and 95% Ar. The solubility limit of the indium filling voids in CoSb3 was found to be close to 0.22. Synchrotron X-ray diffraction refinement of the x = 0.2 sample showed that the indium is located in the classic rattler site and has a substantially larger thermal factor than those of Co and Sb. The electrical resistivity, Seebeck coefficients, and thermal conductivity of the InxCo4Sb12 samples were measured in the temperature range of 300−600 K. All samples showed metal-like behavior, and the large negative Seebeck coefficients indicated n-type conduction. The thermal conductivity decreased with increasing temperature for all samples. A thermoelectric figure-of-merit (ZT) ≥ 1 (n-type) has been achieved when x ≥ 0.2 in InxCo4Sb12 at 575 K.

Journal ArticleDOI
25 Sep 2006
TL;DR: In this paper, a review of recent advances in nanoscale thermal and thermoelectric transport with an emphasis on the impact on integrated circuit (IC) thermal management is presented.
Abstract: In this paper we review recent advances in nanoscale thermal and thermoelectric transport with an emphasis on the impact on integrated circuit (IC) thermal management. We will first review thermal conductivity of low-dimensional solids. Experimental results have shown that phonon surface and interface scattering can lower thermal conductivity of silicon thin films and nanowires in the sub-100-nm range by a factor of two to five. Carbon nanotubes are promising candidates as thermal vias and thermal interface materials due to their inherently high thermal conductivities of thousands of W/mK and high mechanical strength. We then concentrate on the fundamental interaction between heat and electricity, i.e., thermoelectric effects, and how nanostructures are used to modify this interaction. We will review recent experimental and theoretical results on superlattice and quantum dot thermoelectrics as well as solid-state thermionic thin-film devices with embedded metallic nanoparticles. Heat and current spreading in the three-dimensional electrode configuration, allow removal of high-power hot spots in IC chips. Several III-V and silicon heterostructure integrated thermionic (HIT) microcoolers have been fabricated and characterized. They have achieved cooling up to 7 degC at 100 degC ambient temperature with devices on the order of 50 mum in diameter. The cooling power density was also characterized using integrated thin-film heaters; values ranging from 100 to 680 W/cm2 were measured. Response time on the order of 20-40 ms has been demonstrated. Calculations show that with an improvement in material properties, hot spots tens of micrometers in diameter with heat fluxes in excess of 1000 W/cm2 could be cooled down by 20 degC-30 degC. Finally we will review some of the more exotic techniques such as thermotunneling and analyze their potential application to chip cooling

Journal ArticleDOI
TL;DR: In this paper, a polymer-based wafer level fabrication process for micro thermoelectric generators (μTEGs) for the application on non-planar surfaces is presented.
Abstract: We present a novel polymer based wafer level fabrication process for micro thermoelectric generators (μTEGs) for the application on non-planar surfaces The generators are fabricated by subsequent electrochemical deposition (ECD) of Cu and Ni in a 190-μm thick flexible polymer mold formed by photolithographic (PL) patterning of SU-8 First generators were tested and characterized The TEG generated a power of 120 ± 11 nW/cm 2 for a Δ T of 012 K at the μTEG interface, which is equivalent to a thermoelectric efficiency factor of 083 μW K −2 cm −2 The experimental data is in good accordance with a model introduced for the optimization of vertical micro thermoelectric generators It allows calculation of the optimal geometric design parameters for any given material and thermal interfaces The analysis reveals that the thermocouple length should be in the range of 80–150 μm when the best thermoelectric bulk material (BiTe) is used and realistic interface condition are assumed

Journal ArticleDOI
TL;DR: The efficiency of a thermoelectric material is determined by the dimensionless figure of merit as discussed by the authors, which is a function of the temperature difference between the hot and cold ends of the material.
Abstract: Thermoelectric materials convert a temperature difference into electricity and vice versa. [1–3] Such materials utilize the Seebeck effect for power generation and the Peltier effect for cooling. In the Seebeck effect, a temperature difference across a material causes the diffusion of charged carriers across that gradient, thus creating a voltage difference between the hot and cold ends of the material. Conversely, the Peltier effect explains the fact that when current flows through a material a temperature gradient arises because the charged carriers exchange thermal energy. Thermoelectrics perform these functions without moving parts or toxic gases, which make them unique among power generation and cooling methods. Presently, thermoelectrics find only limited use because of their poor efficiency. The efficiency of a thermoelectric material is determined by the dimensionless figure of merit

Journal ArticleDOI
TL;DR: The series of Pb(9.6)Sb(0.2)Te(10)(-)(x)Se(x) compounds with different Se content were prepared, and their structure was investigated at the atomic and nanosized regime level, providing experimental validation of the theoretical concept that embedded nanocrystals can promote strong scattering of acoustic phonons.
Abstract: The series of Pb9.6Sb0.2Te10-xSex compounds with different Se content (x) were prepared, and their structure was investigated at the atomic and nanosized regime level. Thermoelectric properties were measured in the temperature range from 300 to 700 K. The Pb9.6Sb0.2Te10-xSex series was designed after the refinement of the single-crystal structure of Pb3.82Sb0.12Te4 (Pb9.6Sb0.3Te10; S.G. Pm3m) by substituting isoelectronically in anion positions Te by Se. The Pb9.6Sb0.2Te10-xSex compounds show significantly lower lattice thermal conductivity (κL) compared to the well-known PbTe1-xSex solid solutions. For Pb9.6Sb0.2Te3Se7 (x = 7), a κL value as low as 0.40 W/m·K was determined at 700 K. High-resolution transmission electron microscopy of several Pb9.6Sb0.2Te10-xSex samples showed widely distributed Sb-rich nanocrystals in the samples which is the key feature for the strong reduction of the lattice thermal conductivity. The reduction of κL results in a significantly enhanced thermoelectric figure of merit o...

Journal ArticleDOI
TL;DR: In this article, the structural, chemical, and transport properties of Yb2O3 composites are studied, and the maximum figures of merit reach 1.3 for the Yb 0.25Co4Sb12∕Yb 2O3 and 1.2 for Yb0.21Co 4Sb 12∕ Yb 2 O3 at 850K.
Abstract: Composites containing Yb-filled CoSb3 and well-distributed Yb2O3 particles are synthesized by in situ reaction method. The structural, chemical, and transport properties of the composites are studied. Some Yb2O3 particles with microsize locate at the grain boundaries of matrix and others distribute within YbyCo4Sb12 grains as nanoscale inclusions. The combination of the “rattling” of Yb ions inside the voids of CoSb3 and the phonon scattering of the oxide defects results in a remarkable reduction in the lattice thermal conductivity. The thermoelectric performance of the composites is significantly improved, and the maximum figures of merit reach 1.3 for the Yb0.25Co4Sb12∕Yb2O3 and 1.2 for the Yb0.21Co4Sb12∕Yb2O3 composites at 850K.

01 Jan 2006
TL;DR: This paper reviews recent advances in nanoscale thermal and thermoelectric transport with an emphasis on the impact on integrated circuit (IC) thermal management and focuses on the fundamental interaction between heat and electricity, i.e., thermoeLECTric effects, and how nanostructures are used to modify this interaction.
Abstract: In this paper we review recent advances in nanoscale thermal and thermoelectric transport with an emphasis on the impact on integrated circuit (IC) thermal management. We will first review thermal conductivity of low- dimensional solids. Experimental results have shown that phonon surface and interface scattering can lower thermal con- ductivity of silicon thin films and nanowires in the sub-100-nm range by a factor of two to five. Carbon nanotubes are promising candidates as thermal vias and thermal interface materials due to their inherently high thermal conductivities of thousands of W/mK and high mechanical strength. We then concentrate on the fundamental interaction between heat and electricity, i.e., thermoelectric effects, and how nanostructures are used to modify this interaction. We will review recent experimental and theoretical results on superlattice and quantum dot thermoelectrics as well as solid-state thermionic thin-film devices with embedded metallic nanoparticles. Heat and current spreading in the three-dimensional electrode configuration, allow removal of high-power hot spots in IC chips. Several III-V and silicon heterostructure integrated thermionic (HIT) microcoolers have been fabricated and char- acterized. They have achieved cooling up to 7 � C at 100 � C ambient temperature with devices on the order of 50 � mi n diameter. The cooling power density was also characterized using integrated thin-film heaters; values ranging from 100 to 680 W/cm 2 were measured. Response time on the order of 20-40 ms has been demonstrated. Calculations show that with an improvement in material properties, hot spots tens of micrometers in diameter with heat fluxes in excess of 1000 W/cm 2 could be cooled down by 20 � C-30 � C. Finally we will review some of the more exotic techniques such as thermotunneling and analyze their potential application to chip cooling.

Journal ArticleDOI
TL;DR: In this paper, the authors demonstrate that nanostructuring in thermoelectric semiconductors enhances acoustic phonon scattering without the need to prepare solid solutions, without the use of solid solutions.
Abstract: Experimental results are reported that demonstrate that nanostructuring in thermoelectric semiconductors enhances acoustic phonon scattering without the need to prepare solid solutions.

Journal ArticleDOI
TL;DR: In this article, thermoelectric bismuth telluride thin films were prepared on SiO2/Si substrates by radiofrequency (RF) magnetron sputtering.

Journal ArticleDOI
TL;DR: Strontium-filled skutterudites SryCo4Sb12 have been synthesized by a melting method as discussed by the authors, and the filling fraction of Sr in CoSb3 is up to y=0.40, closely consistent with the calculated value by density functional theory methods.
Abstract: Strontium-filled skutterudites SryCo4Sb12 have been synthesized by a melting method. The filling fraction of Sr in CoSb3 skutterudite is up to y=0.40, closely consistent with the calculated value by density functional theory methods. The lattice parameters increase linearly with the increase of Sr content, and the relative change in lattice parameters is in agreement with theoretical prediction. Hall effect measurements have been performed by Van de Pauw method at room temperature. All samples filled with Sr atom exhibit n-type conduction. The thermal and electrical transport properties have been measured in the temperature range of 300–850K. The lattice thermal conductivity of SryCo4Sb12 is significantly depressed as compared to that of the unfilled CoSb3. The dimensionless thermoelectric figure of merit, ZT, increases with increasing temperature and reaches a maximum value of 0.9 for Sr0.28Co4Sb12 at 850K.

Journal ArticleDOI
Gao Min1, David Rowe1
TL;DR: In this paper, a number of prototype thermoelectric refrigerators are investigated and their cooling performances evaluated in terms of the coefficient-of-performance, heat-pumping capacity and cooling-down rate.

Journal ArticleDOI
TL;DR: Ohta et al. as discussed by the authors compared the intrinsic thermoelectric properties of heavily Nb-doped TiO2 to those of heavy Nbdoped SrTiO3 at high temperatures (300-900K).
Abstract: To compare the intrinsic thermoelectric (TE) properties of heavily Nb-doped TiO2 to those of heavily Nb-doped SrTiO3 [S. Ohta et al., Appl. Phys. Lett. 87, 092108 (2005)], the electrical conductivity (σ), carrier concentration (ne), Hall mobility (μHall), and Seebeck coefficient (S) of heavily Nb-doped TiO2 (anatase) epitaxial films were measured at high temperatures (300–900K). The epitaxial films were grown on the (100)-face of LaAlO3 single-crystalline substrates by a pulsed-laser deposition technique at 800°C. The carrier effective mass (m*) of the anatase TiO2 epitaxial films was ∼1m0, which is an order of magnitude smaller than that of Nb-doped SrTiO3 (∼10m0). The estimated TE power factor (S2σ) of the ∼2%-Nb-doped anatase TiO2 film (ne∼5×1020cm−3) was ∼2.5×10−4Wm−1K−2 at 900K, which is approximately 15% of the 20%-Nb-doped SrTiO3 (1.5×10−3Wm−1K−2). The present findings will help establish a future TE material design concept for Ti-based metal oxides.

Journal ArticleDOI
TL;DR: In this paper, a polycrystalline K-filled CoSb3 was synthesized and the uplimit for K filling is at least 0.45, being higher than those of either alkaline earth (AE) or rare-earth (RE) metals but being in consistent with our earlier theoretical prediction.
Abstract: Polycrystalline K-filled CoSb3 are synthesized successfully. The uplimit for K filling is at least 0.45, being higher than those of either alkaline-earth (AE) or rare-earth (RE) metals but being in consistent with our earlier theoretical prediction. The measured transport properties (300–800K) show that K filling does not lower thermal conductivity much in comparison with AE or RE filling due to the relatively low mass of K atom. However, it improves electrical conductivity, retains large Seebeck coefficient, and leads to a reasonably good thermoelectric performance for the filled skutterudites. The maximum figure of merit ZT reaches 1 at 800K for K0.38Co4Sb12.

Journal ArticleDOI
TL;DR: In this article, powder X-ray diffraction, thermal gravimetric, differential scanning calorimetery, and microprobe data were obtained on hot pressed samples of Mg3Sb2.

Journal ArticleDOI
TL;DR: In this article, Bi2Te3 thin and superlattices were grown epitaxially by molecular beam epitaxy on BaF2 substrates with periods of 12 and 6nm, respectively.
Abstract: Multi-quantum-well structures of Bi2Te3 are predicted to have a high thermoelectric figure of merit ZT. Bi2Te3 thin films and Bi2Te3∕Bi2(Te0.88Se0.12)3 superlattices (SLs) were grown epitaxially by molecular beam epitaxy on BaF2 substrates with periods of 12 and 6nm, respectively. Reflection high-energy electron diffraction confirmed a layer-by-layer growth, x-ray diffraction yielded the lattice parameters and SL periods and proved epitaxial growth. The in-plane transport coefficients were measured and the thin films and SL had power factors between 28 and 35μW∕cmK2. The lattice thermal conductivity varied between 1.60W∕mK for Bi2Te3 thin films and 1.01W∕mK for a 10nm SL. The best figures of merit ZT were achieved for the SL; however, the values are slightly smaller than those in bulk materials. Thin films and superlattices were investigated in plan view and cross section by transmission electron microscopy. In the Bi2Te3 thin film and SL the dislocation density was found to be 2×1010cm−2. Bending of the ...

Journal ArticleDOI
TL;DR: In this paper, the authors investigated thermoelectric properties of 20-nb-doped SrTiO 3 at high-temperature (300-1000 K) using single-crystalline epitaxial film, poly-crystaline film (average grain size ∼200 nm).
Abstract: We investigated thermoelectric properties of 20-%-Nb-doped SrTiO 3 at high-temperature (300-1000 K) using single-crystalline epitaxial film, polycrystalline film (average grain size ∼200 nm) and ceramic (average grain size ∼20 μm) samples to clarify the effect of grain boundaries on the thermoelectric performance. Although carrier concentration and Seebeck coefficient of all samples showed no significant differences, Hall mobility of the polycrystalline film was extremely small (<<10 -1 cm 2 V -1 s -1 at 300 K) as compared to those of the epitaxial film and the ceramic sample (∼3 cm 2 V -1 s -1 ). However, it drastically increased with increasing temperature and exhibited the value similar to those of the epitaxial film and the ceramic sample above 700 K. The thermoelectric figure of merit for 20%-Nb-doped SrTiO 3 was found to reach 0.35 at 1000 K irrespective of the grain size.

Journal ArticleDOI
TL;DR: In this article, a combined process of mechanical alloying and spark plasma sintering was used to obtain a high power factor of 1766mW∕mK2 for the Ag08Pb22SbTe20 sample, which corresponds to a high dimensionless figure of merit.
Abstract: Polycrystalline AgnPbmSbTem+2n thermoelectric materials, whose compositions can be described as Ag08Pb18+xSbTe20 were prepared using a combined process of mechanical alloying and spark plasma sintering Electric properties of the sintered samples with different Pb contents were measured from room temperature to 700K The maximum power factor of 1766mW∕mK2 was obtained at 673K for the Ag08Pb22SbTe20 sample, which corresponds to a high dimensionless figure of merit, ZT=137 This best composition is different from that reported before