Showing papers on "Seebeck coefficient published in 2007"
TL;DR: The present approach using a 2DEG provides a new route to realize practical thermoelectric materials without the use of toxic heavy elements and enhances the Seebeck coefficient without reducing the electrical conductivity.
Abstract: Enhancement of the Seebeck coefficient (S ) without reducing the electrical conductivity (sigma) is essential to realize practical thermoelectric materials exhibiting a dimensionless figure of merit (ZT=S2 x sigma x T x kappa-1) exceeding 2, where T is the absolute temperature and kappa is the thermal conductivity. Here, we demonstrate that a high-density two-dimensional electron gas (2DEG) confined within a unit cell layer thickness in SrTiO(3) yields unusually large |S|, approximately five times larger than that of SrTiO(3) bulks, while maintaining a high sigma2DEG. In the best case, we observe |S|=850 microV K-1 and sigma2DEG=1.4 x 10(3) S cm-1. In addition, by using the kappa of bulk single-crystal SrTiO(3) at room temperature, we estimate ZT approximately 2.4 for the 2DEG, corresponding to ZT approximately 0.24 for a complete device having the 2DEG as the active region. The present approach using a 2DEG provides a new route to realize practical thermoelectric materials without the use of toxic heavy elements.
850 citations
TL;DR: In this article, the authors predicted a giant thermoelectric coefficient in a nanostructure consisting of metallic electrodes periodically patterned over graphene, which was deposited on a silicon dioxide substrate.
Abstract: The paper predicts a giant thermoelectric coefficient in a nanostructure consisting of metallic electrodes periodically patterned over graphene, which is deposited on a silicon dioxide substrate. The Seebeck coefficient in this device attains 30mV∕K, this value being among the largest reported ever. The calculations are based on a transfer matrix approach that takes a particular form for graphene-based devices. The results are important for future nanogenerators with applications in the area of sensors, energy harvesting, and scavenging.
243 citations
TL;DR: In this article, it was shown that strongly correlated semiconductor FeSb2 exhibits a colossal Seebeck coefficient of ~−45000μWK−2 cm−1 at 10 K and the thermoelectric power factor PF=S2·ρ−1, where ρ is the electrical resistivity, reaches a record high value of ~2300μWk−2
Abstract: For more than a decade strongly correlated semiconductors and Kondo insulators have been considered as potential thermoelectric materials Such materials have large d- or f-character of the electronic band structure close to the Fermi level that theoretically leads to Seebeck coefficients (S) with large magnitudes In this work it is shown for the first time that the strongly correlated semiconductor FeSb2 exhibits a colossal Seebeck coefficient of ~−45000 μVK−1 at 10 K The thermoelectric power factor PF=S2·ρ−1, where ρ is the electrical resistivity, reaches a record high value of ~2300 μWK−2 cm−1 at 12 K and is 65 times larger than that of the state-of-the-art Bi2Te3-based thermoelectric materials However, due to a large lattice thermal conductivity the dimensionless thermoelectric figure of merit is only 0005 at 12 K Nonetheless, the potential of FeSb2 as a future solid-state thermoelectric cooling device at cryogenic temperatures is underlined
217 citations
TL;DR: The thermoelectric properties of Sb-doped Mg2Si have been characterized by Hall effect measurements at 300 K and by measurements of electrical resistivity (ρ), Seebeck coefficient (S), and thermal conductivity (κ) between 300 and 900 K as mentioned in this paper.
210 citations
TL;DR: In this paper, the authors pin down the origin of the coexistence of the large thermopower and the large conductivity in Na$_x$CoO$_2.
Abstract: In the present study, we pin down the origin of the coexistence of the large thermopower and the large conductivity in Na$_x$CoO$_2$. It is revealed that not just the density of states (DOS), the effective mass, nor the band width, but the peculiar {\it shape} of the $a_{1g}$ band referred to as the "pudding mold" type, which consists of a dispersive portion and a somewhat flat portion, is playing an important role in this phenomenon. The present study provides a new guiding principle for designing good thermoelectric materials.
202 citations
TL;DR: In this article, Bismuth-telluride-based alloy thin-film thermoelectric generators are fabricated by a flash evaporation method and the output voltage and the maximum output power near room temperature are estimated as a function of the temperature difference between hot and cold junctions of the thin-filtered generators.
Abstract: Bismuth–telluride-based alloy thin film thermoelectric generators are fabricated by a flash evaporation method. We prepare Bi 0.4 Te 3.0 Sb 1.6 (p-type) and Bi 2.0 Te 2.7 Se 0.3 (n-type) powders for the fabrication of the flash evaporated thin films. The overall size of the thin film thermoelectric generators, which consist of seven pairs of legs connected by aluminum electrodes, is 20 mm by 15 mm. Each leg is 15 mm long, 1 mm wide and 1 μm thick. We measure the output voltage and estimate the maximum output power near room temperature as a function of the temperature difference between hot and cold junctions of the thin film thermoelectric generators. In order to improve the performance of the generators, a hydrogen annealing process is carried out at several temperatures from 25 °C to 250 °C. The highest output voltage of 83.3 mV and estimated output power of 0.21 μW are obtained from a hydrogen annealing temperature of T a = 250 °C and a temperature difference of Δ T = 30 K. The hydrogen annealing temperature of T a = 250 °C also results in the best electrical performance for both p-type thin film (Seebeck coefficient = 254.4 μV/K, resistivity = 4.1 mΩ cm, power factor = 15.9 μW/cm K 2 ) and n-type thin film (−179.3 μV/K, 1.5 mΩ cm, 21.5 μW/cm K 2 ).
170 citations
TL;DR: In this article, the effect of stretching treatment on the thermoelectric properties of copolymers was examined and the results showed that the stretch treatment significantly increased the electrical conductivity of the copolymer with the highest Seebeck coefficient.
163 citations
TL;DR: In this article, the authors showed that low-dimensional reduction can increase boundary scattering of phonons and reduce lattice thermal conductivity, possibly without negatively affecting the electrical conductivity or Seebeck coefficient.
Abstract: Thermoelectricity is the phenomenon of conversion between thermal and electrical energy. Compared with other technologies, thermoelectric (TE) devices offer distinct advantages: they have no moving parts, contain no chlorofluorocarbons, and have a long lifetime of reliable operation. However, current TE materials have found limited commercial application due to their low efficiency. TE efficiency is related to a material-dependent coefficient, Z, and is often expressed as the dimensionless figure-of-merit, ZT, given by ZT= rS 2 T/j, where Tis the absolute temperature, r is the electrical conductivity, S is the Seebeck coefficient, and j is the total thermal conductivity. It becomes difficult to improve ZT beyond a certain point since the material properties S, r, and j are inter-dependent. [1] Presently, simple bulk materials have reached an upper limit of ZTat approximately 1. Hicks and Dresselhaus proposed that conversion of bulk materials to low dimensional materials might significantly enhance TE performance through phonon scattering and electron confinement effects. [2] Dimensional reduction has since been shown to increase boundary scattering of phonons and reduce lattice thermal conductivity, [3] possibly without negatively affecting the electrical conductivity or Seebeck coefficient. The positive effects of low-dimensionality on ZT have already been demonstrated through several theoretical [2,4–6] and experimental [7] investigations, a few of which were based on lead chalcogenide systems. [8,9] Harman et al. achieved an especially high ZTof 2.0 at 300 K with PbSeTe/PbTe quantum dot superlattices. [10] Bulk
161 citations
TL;DR: In this article, a two-dimensional electron gas (2DEG) in SrTiO3 was used for thermoelectric energy conversion and achieved a Seebeck coefficient of 2.4.
143 citations
TL;DR: It is shown that combined Seebeck coefficient and electrical conductivity measurements provide an effective approach to probing the Fermi Level, carrier concentration and mobility in nanowires.
Abstract: The Seebeck coefficient, electrical conductivity, and thermal conductivity of individual chromium disilicide nanowires were characterized using a suspended microdevice and correlated with the crystal structure and growth direction obtained by transmission electron microscopy on the same nanowires. The obtained thermoelectric figure of merit of the nanowires was comparable to the bulk values. We show that combined Seebeck coefficient and electrical conductivity measurements provide an effective approach to probing the Fermi Level, carrier concentration and mobility in nanowires.
138 citations
TL;DR: In this article, dense lead telluride (PbTe) nanocomposites were prepared from PbTe nanocrystals synthesized employing an aqueous solution-phase reaction.
Abstract: Dense lead telluride (PbTe) nanocomposites were prepared from PbTe nanocrystals synthesized employing an aqueous solution-phase reaction. This approach reproducibly synthesizes 100–150nm nanocrystals with a high yield of over 2g per batch. Densification using spark plasma sintering dimensionally integrated nanoscale grains within a bulk matrix, resulting in a uniform dispersion of nonconglomerated nanocrystals. Transport properties of PbTe nanocomposites were evaluated through temperature dependent resistivity, Hall, Seebeck coefficient, and thermal conductivity measurements. These nanocomposites show an enhancement in the thermoelectric properties compared to bulk polycrystalline PbTe with similar carrier concentrations. Our results also indicate a strong sensitivity to stoichiometry, surface oxygen adsorption, and porosity.
TL;DR: In this paper, the authors investigate the lattice thermal conductivity by modeling the data using the Debye approximation in order to discern the contributions from different phonon-scattering mechanisms.
Abstract: Thermal conductivity, Seebeck coefficient, resistivity, and Hall measurements on polycrystalline ${\mathrm{Mg}}_{2}{\mathrm{Si}}_{1\ensuremath{-}y}{\mathrm{Sb}}_{y}$ with $0\ensuremath{\le}y\ensuremath{\le}0.37$ are reported. In these materials, Sb substitutes for Si in the antifluorite structure. As the Sb content increases, vacancies are formed in the lattice on Mg sites, which also contribute to variations in the transport properties. With increasing Sb content, both the absolute Seebeck coefficient and electrical resistivity first decrease, but then increase due to vacancy formation, while the thermal conductivity decreases monotonically with increasing Sb content. We investigate the lattice thermal conductivity by modeling the data using the Debye approximation in order to discern the contributions from different phonon-scattering mechanisms. We discuss the results in the context of potential thermoelectric applications.
TL;DR: A through-substrate hole under the suspended microdevice allows for transmission electron microscopy characterization of the nanofilm sample assembled on the device, which enables one to correlate the measured thermoelectric properties with the crystal structures of thenanofilms.
Abstract: Measuring in-plane thermoelectric properties of submicron thin films has remained a challenging task. Here we report a method based on a suspended microdevice for four-probe measurements of the Seebeck coefficient, thermal conductivity, electrical conductivity, and thermoelectric figure of merit of patterned indium arsenide (InAs) nanofilms assembled on the microdevice. The contact thermal resistance and intrinsic thermal resistance of the 40nm thick InAs nanofilm sample were measured by using the nanofilm itself as a differential thermocouple to determine the temperature drops at the contacts. The microdevice was also used to measure a 190nm thick silicon dioxide (SiO2) film and the results were compared with those reported in the literature. A through-substrate hole under the suspended microdevice allows for transmission electron microscopy characterization of the nanofilm sample assembled on the device. This capability enables one to correlate the measured thermoelectric properties with the crystal str...
TL;DR: In this article, the electrical conductivity, thermoelectric power, and metal-insulator−semiconductor diode properties of polyaniline prepared in ionic liquid (PANI) have been investigated.
Abstract: The electrical conductivity, thermoelectric power, and metal−insulator−semiconductor diode properties of polyaniline prepared in ionic liquid (PANI) have been investigated. The electrical conductivity of the polyaniline increases exponentially with increasing temperature. The electrical conductivity value at 28 °C is 0.21 S/cm. The Seebeck coefficient of the PANI decreases with increasing temperature. The electrical conductivity and thermoelectric power results suggest that the PANI is a p-type semiconductor polymer. The Al/PANI Schottky diode was fabricated and is a metal−insulator−semiconductor type device. The ideality factor n and barrier height φb values of the diode at 298 K were found to be 2.78 and 0.85 eV, respectively. The barrier inhomogeneities are a very important explanation of the higher values of the ideality factor. The Gaussian distribution function was suggested for describing barrier height inhomogeneities. The standard deviation of the barrier height distribution σo indicates the pres...
TL;DR: The best combination of Seebeck coefficient and conductivity was around 10-7 W m-1 K-2 with copolymers comprising thiophene units alternating with carbazole or indolocarbazole as mentioned in this paper.
Abstract: In a quest for thermoelectric polymeric materials novel polycarbazole and polyindolocarbazole derivatives were synthesized. Alkyl side chains on the carbazole cycle and different side chains (alkyl or benzoyl) on the nitrogen atom of the backbone unit were introduced. Optical, electrochemical, electrical, and thermoelectric properties were investigated on these polymers and on two poly(diindolocarbazole)s. Band structure calculations were used to predict which polymers might be promising as thermoelectric materials. The best combination of Seebeck coefficient and conductivity (power factor) was around 10-7 W m-1 K-2 with copolymers comprising thiophene units alternating with carbazole or indolocarbazole. This family of polymers possesses good Seebeck coefficients, but there is still a need to improve the electrical conductivity, to produce useful thermoelectric materials.
TL;DR: In this paper, the effect of Hf alloying on Ti site, Pt and Pd alloys on Ni site, and Sb doping on Sn site for the optimization of thermoelectric properties of TiNiSn-based compounds was investigated.
TL;DR: In this paper, a half-Heusler material with randomly distributed TiO2 particles has been synthesized by arc melting and annealing, and the temperature range of ∼300-850 K was measured.
Abstract: TiFexCo1−xSb half-Heusler materials with randomly distributed TiO2 particles have been synthesized by arc melting and annealing. Thermoelectric properties were measured in the temperature range of ∼300–850 K. TiCoSb shows n-type conduction, while TiFexCo1−xSb transfers to p-type conduction when x≥0.01. The electrical conductivity of p-type TiFexCo1−xSb increased with increasing Fe content. The maximum Seebeck coefficient reached about 300 μV/K at 850 K for x=0.15. Since Fe powder contained a trace of Fe2O3, a small amount of TiO2 particles formed during the synthesis process. The lattice thermal conductivity dramatically decreased with increasing Fe content, which was mostly caused by the introduction of in situ formed TiO2 particles, as well as the effects of mass fluctuation and strain field fluctuation due to the substitution of Fe to the Co site. The dimensionless figure of merit (ZT=S2σT/κ) was significantly improved over the whole temperature region, and a maximum ZT value of 0.45 has been obtained ...
TL;DR: In this article, the effects of Si substitution on the temperature-dependent electrical resistivity, Seebeck coefficient, as well as thermal conductivity in the Heusler-type compound was investigated.
Abstract: We report the effects of Si substitution on the temperature-dependent electrical resistivity, Seebeck coefficient, as well as thermal conductivity in the Heusler-type compound ${\mathrm{Fe}}_{2}\mathrm{VAl}$ It is found that the substitution of Si onto the Al sites causes a significant decrease in the electrical resistivity and lattice thermal conductivity A theoretical analysis indicated that the reduction of lattice thermal conductivity arises mainly from point-defect scattering of the phonons With slight substitution, the Seebeck coefficient changes sign from positive to negative, accompanied by the appearance of a broad minimum at high temperatures These features are associated with the change in the electronic band structure, where the Fermi level shifts upwards from the center of the pseudogap due to electron-doping effect For $xg01$ in ${\mathrm{Fe}}_{2}{\mathrm{VAl}}_{1\ensuremath{-}x}{\mathrm{Si}}_{x}$, no broad minimum in the Seebeck coefficient appears, indicative of a dramatic modification in the band structure of these materials While the thermoelectric performance improves with increasing Si concentration, the largest figure-of-merit $ZT$ value among these alloys is still an order of magnitude lower than conventional thermoelectric materials
TL;DR: In this paper, Bismuth sulfide thin films have been assembled by cross-linkage nanorods on surface-functionalized Si substrate with self-assembled monolayers.
Abstract: Bismuth sulfide thin films have been assembled by cross-linkage nanorods on surface-functionalized Si substrate with self-assembled monolayers. Results of transmission electron microscopy and electron diffraction revealed that highly crystalline Bi2S3 nanorods grow along c-axis direction. Electrical transport properties including resistivity (0.02Ωcm), thermopower (−755μVK−1), and carrier mobilities (1100cm2V−1s−1) of the Bi2S3 films at 300K are found superior to those of previously reported Bi2S3 samples. The Bi2S3 films exhibit a maximum thermoelectric power factor (3.97×10−3Wm−1K−2) at 450K. The enhancement of thermoelectric properties mainly originates from highly crystalline and oriented nanostructures embedded in the Bi2S3 films.
TL;DR: The thermoelectric properties of PbTe within the NaCl (B1) and the orthorhombic $Pnma$ phases are extensively studied by ab initio calculations using the full-potential linearized augmented plane-wave method and the semiclassical Boltzmann theory as mentioned in this paper.
Abstract: The thermoelectric properties of PbTe within the NaCl (B1) and the orthorhombic $Pnma$ phases are extensively studied by ab initio calculations using the full-potential linearized augmented plane-wave method and the semiclassical Boltzmann theory. The calculations of $n$- and $p$-type Seebeck coefficients for the B1 structure suggested that the energy band gap plays an important role in determining the thermoelectric properties, but only at lower carrier concentrations. We found that the $n$-doped $Pnma$ phase at $6.5\phantom{\rule{0.3em}{0ex}}\mathrm{GPa}$ has a larger Seebeck coefficient than that of the $n$-doped B1 phase at zero pressure, but has a comparable electric conductivity. This fact could be well understood by the large density of states in the conduction band and the large anisotropy in the band structure and constant energy surface. Our calculations also predicted that the largest $n$-type ZT values at 300 and $600\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ of the $Pnma$ phase at $6.5\phantom{\rule{0.3em}{0ex}}\mathrm{GPa}$ can reach up to 0.9 and 1.59, respectively, which are two times larger than those in B1 phase at zero pressure. The current theory strongly suggests that the $Pnma$ structure of PbTe is an excellent thermoelectric material. It is desirable to synthesize the $Pnma$ phase of PbTe at ambient pressure by making use of its high performance.
TL;DR: In this article, the authors developed a transport theory involving resistivity and Hall coefficient on the basis of the microscopic Fermi liquid theory, by considering the current vertex correction (CVC).
Abstract: In many strongly correlated electron systems, remarkable violation of the relaxation time approximation (RTA) is observed. The most famous example would be high-Tc superconductors (HTSCs), and similar anomalous transport phenomena have been observed in metals near their antiferromagnetic (AF) quantum critical point (QCP). Here, we develop a transport theory involving resistivity and Hall coefficient on the basis of the microscopic Fermi liquid theory, by considering the current vertex correction (CVC). In nearly AF Fermi liquids, the CVC accounts for the significant enhancements in the Hall coefficient, magnetoresistance, thermoelectric power, and Nernst coefficient in nearly AF metals. According to the numerical study, aspects of anomalous transport phenomena in HTSC are explained in a unified way by considering the CVC, without introducing any fitting parameters; this strongly supports the idea that HTSCs are Fermi liquids with strong AF fluctuations. In addition, the striking \omega-dependence of the AC Hall coefficient and the remarkable effects of impurities on the transport coefficients in HTSCs appear to fit naturally into the present theory. The present theory also explains very similar anomalous transport phenomena occurring in CeCoIn5 and CeRhIn5, which is a heavy-fermion system near the AF QCP, and in the organic superconductor \kappa-(BEDT-TTF).
TL;DR: In this paper, the authors used electron beam lithography to measure the thermopower and electrical conductivity of an individual indium antimonide (InSb) nanowire grown using a vapor-liquid solid method.
Abstract: It has been suggested by theoretical calculation that indium antimonide (InSb) nanowires can possess improved thermoelectric properties compared to the corresponding bulk crystal. Here we fabricated a device using electron beam lithography to measure the thermopower and electrical conductivity of an individual InSb nanowire grown using a vapor-liquid-solid method. The comparison between the measurement results and transport simulations reveals that the nanowire was unintentionally degenerately doped with donors. Better control of the impurity doping concentration can improve the thermoelectric properties.
TL;DR: In this paper, the thermal conductivity of n-type nanocrystalline bismuth-telluride-based thin films (Bi2.0Te2.7Se0.3) is investigated by a differential 3ω method at room temperature.
Abstract: The thermal conductivity of n-type nanocrystalline bismuth-telluride-based thin films (Bi2.0Te2.7Se0.3) is investigated by a differential 3ω method at room temperature. The nanocrystalline thin films are grown on a glass substrate by a flash evaporation method, followed by hydrogen annealing at 250 °C. The structure of the thin films is studied by means of atomic force microscopy, x-ray diffraction, and energy-dispersive x-ray spectroscopy. The thin films exhibit an average grain size of 60 nm and a cross-plane thermal conductivity of 0.8 W∕m K. The in-plane electrical conductivity and in-plane Seebeck coefficient are also investigated. Assuming that the in-plane thermal conductivity of the thin films is identical to that of the cross-plane direction, the in-plane figure of merit of the thin films is estimated to be ZT=0.7. As compared with a sintered bulk sample with average grain size of 30 μm and nearly the same composition as the thin films, the nanocrystalline thin films show approximately a 50% redu...
TL;DR: In this paper, two textured p-type Bi0.4Sb1.6Te3 samples were prepared using a powder metallurgy approach, with the c axis parallel to the pressing direction.
Abstract: This work is concerned with Bi2Te3-based compounds known as being highly effective materials for thermoelectric applications near room temperature. These compounds are characterized by a remarkable anisotropy linked to their R3¯m crystal structure. Two textured p-type Bi0.4Sb1.6Te3 samples were prepared using a powder metallurgy approach, with the c axis parallel to the pressing direction. One sample was undoped while the second was doped with Pb which acts as an acceptor. The electrical conductivity, Hall coefficient, and magnetoresistivity were measured from room temperature down to 6K. The Seebeck coefficient α and electrical conductivity σ were measured along and perpendicular to the c axis from 300 up to 550K, and the thermal conductivity κ was measured at 300K. Different values of Seebeck coefficient were observed along and perpendicular to the c axis at temperatures above Ti, the beginning of intrinsic region in which the influence of the minority carriers becomes significant. Below Ti, the Seebeck...
TL;DR: In this article, the average grain size increases with excess Sb content, abnormally grown by about 100 times as the excess sb is up to 4 at.%. A liquid-phase-related mechanism is used to explain the abnormal growth.
Abstract: Volatilization of Sb during the fabrication of CoSb3 by mechanical alloying and then spark plasma sintering has been successfully compensated by adding excess Sb. The average grain size increases apparently with excess Sb content, abnormally grown by about 100 times as the excess Sb is up to 4 at.%. A liquid-phase-related mechanism is used to explain the abnormal growth. The uncompensated sample shows a negative Seebeck coefficient near room temperature, while the sample compensated with 6 at.% excess Sb shows an intrinsic positive Seebeck coefficient and an enhanced ZT value, which has a maximum of about 0.1 at 350 °C, which is two times higher than the uncompensated one. The transition of electrical conductivity from n- to p-type relative to the Sb compensation is discussed in relation to the point defect. A defect equation is given to show the nature of electron generation due to Sb deficiency. The Sb-vacancy not only provides extrinsic carrier but also generates a significant impact on the band gap and hence on the Seebeck coefficient.
TL;DR: In this paper, the crystal structures, magnetic susceptibilities and thermoelectric properties of a delafossite-type oxide, CuCr1-xMgxO2 (0 ≤x ≤0.05) at temperatures in the range from 4 to 1100 K.
Abstract: We report the crystal structures, magnetic susceptibilities and thermoelectric properties of a delafossite-type oxide, CuCr1-xMgxO2 (0 ≤x ≤0.05) at temperatures in the range from 4 to 1100 K. The lattice parameter, c, linearly decreases with increasing Mg concentration in the range 0 ≤x ≤0.03. This decrease is mainly caused by the shrinking of O–Cu–O dumbbells which connect the CdI2-type (Cr/Mg)O2 slabs. Magnetic susceptibility measurements indicate that Cr3+ is in the high spin state in the paramagnetic phase above 25 K. The electrical resistivity, ρ, of CuCr1-xMgxO2 exhibits semiconducting behavior (dρ/dT < 0) in the range from 350 to 1100 K, which decreases through the partial substitution of Mg2+ for Cr3+ with 0 ≤x ≤0.03. Positive and high Seebeck coefficients of CuCr1-xMgxO2 at high temperatures are consistant with the theoretical values predicted by Koshibae, who considered the spin entropy flux for the high-temperature Seebeck coefficent. From the linear S vs ln σ plot, considerable contribution from the band structure and carrier concentraton to the Seebeck coefficient is indicated. The power factor, S2σ, reaches its maximum value at around x = 0.03 in this system. The thermal conductivity, κ, for CuCr1-xMgxO2 ranges from 6 to 10 Wm-1K-1 at 300 K, slowly decreasing with increasing temperature up to 1000 K. In the present system, the maximum dimensionless figure of merit, ZT=S2T/ρκ= 0.04, is realized for the case of x = 0.03 at 950 K.
TL;DR: Barium and indium double-filled skutterudites have been synthesized by a melting method using a series of starting materials with nominal compositions Ba0.13In0.14Co4Sb11 as mentioned in this paper.
Abstract: Barium and indium double-filled skutterudites BaxInyCo4Sb12−z have been synthesized by a melting method using a series of starting materials with nominal compositions Ba0.3−mInmCo4Sb12 (0⩽m⩽0.3). Rietveld structure refinement shows that both barium and indium occupied the Sb-icosahedron voids in skutterudite structure. The thermal vibration parameter Uiso of indium is an order of magnitude bigger than that of barium. The electron probe microanalysis data prove that the filling fraction limit of indium is about 0.22. Hall effect was measured by the Van de Pauw method at room temperature. All BaxInyCo4Sb12−z compounds exhibit n-type conduction. The temperature dependences of electrical conductivity, Seebeck coefficient, and thermal conductivity have been measured on these compounds in the range of 300–850K. Ba0.13In0.14Co4Sb11.75 with close filling fractions for barium and indium exhibits anomalously excellent thermoelectric properties, which may be due to the presence of the localized state in the gap occu...
TL;DR: In this paper, a single phase of polycrystalline Mg 2 Si was grown using the vertical Bridgman method in a nonwetting growth environment, achieved by the use of an anti-adhesion coating on the crucible wall.
TL;DR: The thermal conductivity obtained from NEMD simulations is found to be in very good agreement with that obtained through Green-Kubo EMD simulations for a binary ionic mixture, which points to a possible cancellation between the neglected "partial enthalpy" contribution to the heat flux associated with the interdiffusion of one species through the other.
Abstract: The thermal conductivity of molten NaCl and KCl was calculated through the Evans-Gillan nonequilibrium molecular dynamics (NEMD) algorithm and Green-Kubo equilibrium molecular dynamics (EMD) simulations. The EMD simulations were performed for a “binary” ionic mixture and the NEMD simulations assumed a pure system for reasons discussed in this work. The cross thermoelectric coefficient obtained from Green-Kubo EMD simulations is discussed in terms of the homogeneous thermoelectric power or Seebeck coefficient of these materials. The thermal conductivity obtained from NEMD simulations is found to be in very good agreement with that obtained through Green-Kubo EMD simulations for a binary ionic mixture. This result points to a possible cancellation between the neglected “partial enthalpy” contribution to the heat flux associated with the interdiffusion of one species through the other and that part of the thermal conductivity related to the coupled fluxes of charge and heat in “binary” ionic mixtures.
TL;DR: In this article, a compositional thermoelectric phase diagram for high-quality epitaxial films composed of 20%-Nb-doped CaTiO3 and 20-nb-decomposition Nb-Doped CaSiO3 was proposed, which includes the density of states effective mass (md*) carrier relaxation time (τ), and thermodynamic power factor (S2σ), where S and σ are Seebeck coefficient and electrical conductivity).
Abstract: Herein the authors propose a compositional thermoelectric phase diagram, which includes the density of states effective mass (md*) carrier relaxation time (τ), and thermoelectric power factor (S2σ, where S and σ are Seebeck coefficient and electrical conductivity) for high-quality epitaxial films composed of 20%-Nb-doped CaTiO3–SrTiO3–BaTiO3 solid solutions [(Ca,Sr,Ba)(Ti08Nb02)O3] The md* values almost proportionally increase with the in-plane lattice parameter of (Ca,Sr,Ba)(Ti08Nb02)O3 epitaxial film, while the τ values drastically decrease when Ca and/or Ba are substituted for Sr in Sr(Ti08Nb02)O3, indicating that the Sr-site substitution negatively affects the thermoelectric performance of Nb-doped SrTiO3