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Showing papers on "Thermoelectric effect published in 1995"


BookDOI
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


Journal ArticleDOI
TL;DR: In this article, the electrical conductivity and Seebeck coefficient as a function of the Co Fe ratio and temperature were investigated in the La0.8Sr0.2Co1−yFeyO3 with 0 ≤ y ≤ 1.

746 citations


01 Jan 1995
TL;DR: In this paper, the ZT for PGEC relaxation of A,,.34.4.4 Introduction Systematic Search Historical Review New Materials Phonon "Glasses" Desired Performance PGEC Relaxation of A,.
Abstract: 34.4 Introduction Systematic Search Historical Review New Materials Phonon "Glasses" Desired Performance PGEC Relaxation of A,,. Assumption Band Gaps of Semiconductors Carrier Mobilities Background Explanation Electronegativities and Good Thermoelectric Semiconductors Dopant and Mixed-Crystal Effects on Mobilities Dopant Effects on the Weighted Mobility Mixed-Crystal Effects on Mobility Weighted Mobility Lattice Thermal Conductivity Phonon Scattering Mechanisms New Amin Crystals and New Thermoelectrics Conclusions From the Analysis Appendix: Calculation of ZT for PGEC References

341 citations


Journal ArticleDOI
TL;DR: In this paper, the electrical transport properties of (Ca0.9MnO3(M = Y, La, Ce, Sm, In, Sn, Sb, Pb, Bi) are investigated in terms of a new material for high-temperature thermoelectric conversion.

314 citations


Journal ArticleDOI
TL;DR: Seebeck as mentioned in this paper reported electrical and thermal conductivity data on CoSb3, and doped and undoped alloys of Co1−x Ir x Sb3−y As y from 20 to 700 K.
Abstract: Seebeck, electrical, and thermal conductivity data are reported on CoSb3, and doped and undoped alloys of Co1−x Ir x Sb3−y As y from 20 to 700 K. n‐type semiconductors were obtained by doping with Ni, Te, or Pd, and the hole concentration in p‐type samples was increased by substitution of Fe, Ru, Os, and Ge. An estimated maximum value for ZT of 0.6 (Z is the figure of merit) was found for a Te‐doped (n‐type) alloy at 700 K. For p‐type alloys, the maximum value of ZT was found to be 0.3 at 550 K. Electrical and thermal transport data also are reported for CoAs3, RhSb3, and IrSb3. Most of the samples investigated were polycrystalline, but a few measurements on CoSb3 single crystals also are discussed.

271 citations


Patent
23 Oct 1995
TL;DR: In this paper, a temperature control device for regulating temperature, preferably a thermoelectric device comprising Peltier elements, is described. And a planar column device and a total analysis system for liquid phase analysis are presented.
Abstract: Miniaturized planar column devices and miniaturized total analysis systems for liquid phase analysis are disclosed. The systems include a temperature control device for regulating temperature, preferably a thermoelectric device comprising Peltier elements.

164 citations


Journal ArticleDOI
TL;DR: In this article, the electrical conductivity and the Seebeck coefficient of Cu 2 O were measured as a function of temperature and oxygen partial pressure, and the results indicated that the dominant electronic charge carriers are holes.

110 citations


Journal ArticleDOI
TL;DR: In this paper, the authors describe micromachined IR thermopiles based on polysilicon and aluminium for the contactless measurement of surface temperature, which shows high detectivity and very small temperature dependence of responsivity.
Abstract: Unlike the 'classical' thermoelectric materials bismuth and antimony, the sensor material silicon allows a good compatibility to CMOS-standard IC processes. This paper describes micromachined IR thermopiles based on polysilicon and aluminium for the contactless measurement of surface temperature. The sensor performance shows high detectivity and very small temperature dependence of responsivity.

109 citations


Journal ArticleDOI
TL;DR: In this paper, a combined theoretical/experimental study of the heat transfer in thermoelectric shape memory alloy (SMA) actuators is undertaken, where a one-dimensional model is developed and transient temperatures in the SMA are evaluated for different applied electric current densities.
Abstract: A combined theoretical/experimental study of the heat transfer in thermoelectric shape memory alloy (SMA) actuators is undertaken in this paper. A one-dimensional model of a thermoelectric unit cell with a SMA junction is developed first and the transient temperatures in the SMA are evaluated for different applied electric current densities. As a first step towards the design of an actuator, a thermoelectric module is assembled in the laboratory for cooling/heating the SMA. Transient temperature profiles are recorded for the monotonic heating and cooling runs for two different materials-copper and SMA (with or without the phase transformation). These recorded profiles are then compared with the predictions from the model; the agreement is reasonable, particularly during the cooling process. Temperature profiles are also recorded for cyclic cooling and heating of copper at a frequency of 0.5 Hz and a good comparison is obtained. Theoretical predictions for thermal cycling of SMA show that it is possible to achieve a frequency of 2 Hz on full phase transformation and 17 Hz on partial transformation of 25%.

109 citations


Patent
07 Jun 1995
TL;DR: In this article, an improved thermoelectric heat exchanger is provided which comprises a series of heat exchangers sandwiched between two channels for the purpose of transferring heat from a liquid coolant flowing through one channel to another fluid flowing through the other channel.
Abstract: An improved thermoelectric heat exchanger is provided which comprises a series of thermoelectric units sandwiched between two channels for the purpose of transferring heat from a liquid coolant flowing through one channel to a second fluid flowing through the other channel. Heat transfer fins are brazed to the inner surfaces of both channels to provide improved heat transfer between the fluids and the channels. A thermally conductive grease or ductile metal between the thermoelectric units and the channels provides improved heat transfer at this interface. When an electric current is passed through the thermoelectric units, heat is transferred from the liquid coolant through the thermoelectric units to the second fluid via the Peltier Effect.

108 citations


Journal ArticleDOI
TL;DR: In this article, a single couple thermoelectric generator consisting of n-type FeSi2 and p-type higher manganese silicide was developed and characterized using the Peltier effect.
Abstract: Single couple thermoelectric generators consisting of n-type FeSi2 and p-type higher manganese silicide were developed and characterized. The leg and the bridge materials were prepared by a powder metallurgical method. Using the Peltier effect the transport properties were measured over the whole working temperature range. Electrical contacts suitable for the hot side could be obtained by conventional vacuum soldering and those for the cold side by ultrasonic soldering. The measured efficiency was in excellent agreement with the calculated values derived from the leg and contact properties.

Journal ArticleDOI
TL;DR: In this paper, a theoretical framework for estimating the effects of a superlattice on the thermoelectric (TE) transport in semiconductors is presented, where the authors consider both transverse and parallel conduction through the SL, and in the latter case the possibility of modulation doping.
Abstract: We present a theoretical framework for estimating the effects of a superlattice (SL) on the thermoelectric (TE) transport in semiconductors. We consider both transverse and parallel conduction through the SL, and in the latter case, the possibility of modulation doping. Our calculations of electron and phonon transport are based on a two‐band single‐valley model for heavily doped n‐type Si80Ge20, with modifications to account for the effects of parallel and transverse transport through a SL. For parallel transport, we find modest improvement in the TE figure‐of‐merit, only for the narrowest SL (5.4 A). For transverse conduction, we find that if the SL can be designed to inhibit the conduction of low‐energy carriers, then large improvements in the TE figure‐of‐merit are possible, as large as +100% over the bulk.

Journal ArticleDOI
TL;DR: In this paper, the quantum-dot refrigerator (QDR) and the normal-insulator-superconductor (NIS) refrigerators were compared and it was shown that the best refrigeration is obtained with the electronic distribution far from the equilibrium Fermi-Dirac function and the temperature reduction achieved is limited by the rate at which phonons are absorbed.
Abstract: Thermoelectric cooling, based upon the extraction of hot electrons and holes from a metallic electron gas, holds unrealized potential for refrigeration at cryogenic temperatures. We discuss the performance of two such electronic refrigerators: the quantum-dot refrigerator (QDR) and the normal-insulator-superconductor (NIS) refrigerator. We obtain the QDR base temperature using a numerical simulation and verify the validity of certain simplifying assumptions which allow refrigerating performance to be summarized on a diagram of ambient temperature versus electronic temperature. In this way, we find that the best refrigeration is obtained with the electronic distribution far from the equilibrium Fermi-Dirac function and the temperature reduction achieved is limited by the rate at which phonons are absorbed. We predict that, with sufficient thermal isolation, electronic devices could be cooled to a small fraction of the ambient temperature using these solid-state refrigerators. The NIS refrigerator should be capable of cooling thin-film devices from above 300 mK to below 100 mK; the QDR will cool macroscopic metallic samples in the \ensuremath{\mu}K or nK range. We also discuss topics related to thermoelectric refrigeration including other cryogenic thermoelectric cooling schemes, the validity of the linear-response theory of thermoelectric effects, the refrigerating efficiency of an optimized thermoelectric refrigerator, and the overall cooling power of thermoelectric refrigeration.

Patent
19 Dec 1995
TL;DR: In this paper, an improved thermoelectric temperature control system for selectively heating or cooling a temperature control fluid to be provided through an exit conduit to an external thermal load and returned to the system through an inlet conduit.
Abstract: An improved thermoelectric temperature control system for selectively heating or cooling a temperature control fluid to be provided through an exit conduit to an external thermal load and returned to the system through an inlet conduit. The system having at least a first liquid heat exchanger, a thermoelectric module in thermal conductivity with the liquid heat exchanger, a heat sink in thermal conductivity with the thermoelectric module, a pump and connecting conduits to move the temperature control fluid from the inlet conduit through the pump and liquid heat exchanger to the exit conduit and power and control electronics to activate the pump and thermoelectric module. The improvement comprises a thermal capacitor connected for fluid communication with the external thermal load and the thermoelectric temperature control system to provide thermal wattage to the external thermal load via the temperature control fluid in addition to the thermal wattage provided to the external thermal load by the thermoelectric temperature control system during the real-time use of the thermoelectric temperature control system. An alternate embodiment includes a liquid-to-liquid heat exchanger system to improve the efficiency of the system.

Journal ArticleDOI
TL;DR: It is shown that heat and electronic conduction through the barriers has a pronounced effect on the thermoelectric properties of the superlattice and that the figure of merit is decreased substantially for finite barrier thicknesses.
Abstract: The thermoelectric properties of systems in the form of superlattices have been studied. First, the electrical and thermal conductivities, the thermopowers, and the figures of merit of superlattice structures are given in terms of the bulk parameters of the two constituent materials for conduction both parallel and perpendicular to the superlattice axis. Second, systems in which the layers of one of the materials become sufficiently thin that their electronic properties become effectively those of a two-dimensional quantum well are considered. Numerical calculations are given for such systems with ${\mathrm{Bi}}_{2}$${\mathrm{Te}}_{3}$ quantum wells separated by barriers having the parameters of bulk ${\mathrm{Pb}}_{0.75}$${\mathrm{Sn}}_{0.25}$Te. It is shown that heat and electronic conduction through the barriers has a pronounced effect on the thermoelectric properties of the superlattice and that the figure of merit is decreased substantially for finite barrier thicknesses.

Journal ArticleDOI
01 Apr 1995
TL;DR: In this paper, the AC-DC transfer differences of thermal converters due to thermoelectric effects in the heater circuit are directly measured with a fast reversed DC to an uncertainty of a few parts in 10/sup 7.
Abstract: The AC-DC transfer differences of thermal converters due to thermoelectric effects in the heater circuit are directly measured with a fast reversed DC to an uncertainty of a few parts in 10/sup 7/. This new and independent method allows former theoretical methods for evaluating thermoelectric effects in thermal converters to be checked. >

Journal ArticleDOI
TL;DR: In this article, the effects of tunneling through the barriers due to finite potential offsets and of the thermal currents through the barrier layers are shown to be essential to describe properly the thermoelectric figure of merit of realistic quantum wire superlattices.
Abstract: The electrical conductivity, the thermoelectric power, and the electrical contribution to the thermal conductivity of quantum wire superlattices have been studied. The effects of tunneling through the barriers due to finite potential off‐sets and of the thermal currents through the barrier layers are shown to be essential to describe properly the thermoelectric figure of merit of realistic quantum wire superlattices. The figure of merit exhibits a maximum as a function of superlattice period which, for large barrier off‐sets, is found to be substantially enhanced over that for the bulk material and also larger than that for quantum well superlattices.

Patent
14 Jul 1995
TL;DR: In this paper, a power control circuit for improved temperature control of thermoelectric devices to maintain the temperature of the devices at a set point is presented. But the circuit is not suitable for outdoor applications.
Abstract: A power control circuit for improved temperature control of thermoelectric devices to maintain the temperature of thermoelectric devices at a set point. The circuit includes a rectifying device to provide rectified alternating current when receiving an input from an electrical power source; a flyback power supply to supply a DC voltage to the thermoelectric device; a switching device to modulate the rectified alternating current across the primary of the flyback transformer; sensor circuitry to monitor the temperature of the thermoelectric device; and a programmable control device to receive an output from the sensor circuitry and provide a control signal to the switching device, the control signal being determined by the difference between the sensed temperature of the thermoelectric device and the desired set point to allow the DC voltage to the thermoelectric device to bring the temperature of the thermoelectric device to the set point and maintain the temperature of the thermoelectric device at the set point.

Book
01 Jan 1995
TL;DR: The Emf in Thermocouples and their properties can be found in this article, where standard reference functions for thermocouple Emf are defined. But they do not consider the uncertainty in temperature measurement.
Abstract: The Emf in Thermocouples.- Thermocouple Materials and their Properties.- Thermocouples in Use.- The Calibration of Thermocouples.- The Uncertainty in Temperature Measurement.- Multi-Site Temperature Measurement.- The Thermodynamics of Thermoelectricity.- Standard Reference Functions for Thermocouple Emf. Bibliography.

Journal ArticleDOI
TL;DR: In this article, the Dufour energy flux density and thermal diffusion were applied to electrolytic solutions and the electrode interface to clarify the quantitative description of heat generation at an interface and its relationship to the temperature dependence of the open-circuit potential of thermogalvanic cells.
Abstract: Fundamental multicomponent transport equations, including thermal diffusion and the Dufour energy flux density, are applied to electrolytic solutions and the electrode interface to clarify the quantitative description of heat generation at an interface and its relationship to the temperature dependence of the open-circuit potential of thermogalvanic cells.

Journal ArticleDOI
TL;DR: Normal state YBa2Cu3O7−δ films, epitaxially grown "off-c axis" with tilt angles up to 20°, are shown to be fast thermoelectric detectors for radiation from UV to far infrared wavelengths as mentioned in this paper.
Abstract: Normal state YBa2Cu3O7−δ films, epitaxially grown ‘‘off‐c axis’’ with tilt angles up to 20° are shown to be fast thermoelectric detectors for radiation from UV to far infrared wavelengths. Upon radiation heating of the tilted films a thermoelectric voltage arises due to the anisotropy of the thermopower in YBa2Cu3O7−δ. The response time is limited by the decaying temperature gradient and thus by heat diffusion. For thin films we have measured a response time from ≲1 ns in the UV to ∼5 ns in the far infrared. Because of the wavelength dependent reflectivity, the responsivity of the films varies between 0.5 V/MW and 20 V/MW. Thus, thin tilted YBa2Cu3O7−δ films can be used as fast room temperature detectors over a wide spectral range.

Journal ArticleDOI
TL;DR: In this article, a powder of nominal composition Fe 3o Si 70 was found to transform to a homogeneous β-FeSi 2 phase in the as milled condition, and the appropriate milling time of a powder for sintering was considered to be 720 ks.
Abstract: MA has been applied to the Fe-Si system near the composition FeSi 2 starting from elemental powders using a horizontal ball mill. Powders were examined by means of XRD and DSC. After substantially long time milling, the premixed powder of nominal composition Fe 3o Si 70 was found to transform to a homogeneous β-FeSi 2 phase in the as milled condition. The appropriate milling time of a powder for sintering was considered to be 720 ks. At this stage the powder consists of very fine Fe and Si crystals in the as milled condition. This transforms into a homogeneous β phase with an exothermic reaction at around 720 K. The transformation rate from (α + e) to β in the MA powder was found to be faster than that in the specimen prepared from an eutectic alloy ingot. Specimens prepared by hot pressing from MA powder showed smaller grain size and lower thermal conductivity than those prepared by ingot metallurgy. The p-type thermoelectric properties were measured for β-FeSi 5 hot-press sintered specimens doped with both Al and Mn. Due to a small grain size, the specimen prepared from the MA powder showed a higher figure of merit and hence is, higher in conversion efficiency than that prepared by ingot metallurgy. The sequence of phase formation by mechanical alloying and post-milling annealing is considered. The effects of grain size on the thermal conductivity and Seebeck potential are discussed.


Patent
21 Apr 1995
TL;DR: In this paper, an integrated circuit package with an internal cooling device is presented, where a thermoelectric device operates according to the Peltier cooling effect, and the second plate is disposed within the chamber apart from the package substrate.
Abstract: An integrated circuit package having an internal cooling device. The integrated circuit package includes a thermoelectric device that operates according to the Peltier cooling effect. The thermoelectric device includes a first plate and a second plate that are thermally connected by a plurality of conducting elements. A package substrate is attached to the first plate such that a chamber is formed. The second plate is disposed within the chamber apart from the package substrate. The second plate is cooled when power is supplied to the thermoelectric device. By disposing an integrated circuit chip on the second plate and evaluating the chamber, the integrated circuit chip may be cooled to a sub-ambient temperature without internal or external condensation.

Patent
23 May 1995
TL;DR: In this article, a P-type thermoelectric material plate is bonded to the surface of the first substrate having the electrodes, and an N-type polycrystalline material plate was attached to the surfaces of the second substrate having electrodes.
Abstract: A method of making a thermoelectric device comprises forming electrodes on a surface of a first substrate and on a surface of a second substrate. Thereafter, a P-type thermoelectric material plate is bonded to the surface of the first substrate having the electrodes, and an N-type thermoelectric material plate is bonded to the surface of the second substrate having the electrodes. Each of the thermoelectric material plates are then processed by cutting and removing portions thereof to form P-type and N-type thermoelectric material chips bonded to the first and second substrates, respectively. Thereafter, the N-type thermoelectric material chips of the second substrate are bonded to the electrodes of the first substrate, and the P-type thermoelectric material chips of the first substrate are bonded to the electrodes of the second substrate to form PN-junctions between the first and second substrates.

Patent
23 Aug 1995
TL;DR: In this article, the Peltier effect was used to control the temperature of the "cold" surface of the thermoelectric module to obtain cooling of an injured animal limb to a temperature between 13 and 18 DEG C.
Abstract: Apparatus for cooling a limb including a thermoelectric module (2) which operates by the Peltier effect A heat sink (6) is in contact with the "hot" surface of the module (2) to dissipate heat therefrom A reservoir (19, figure 4) contains cooling fluid for cooling the heat sink (6), a pump circulates the cooling fluid, and a refrigeration unit cools the cooling fluid The apparatus provides control of the temperature of the "cold" surface of the thermoelectric module (2), to obtain cooling of an injured animal limb to a temperature between 13 and 18 DEG C, or to sub-zero temperatures to treat skin cancer

Journal ArticleDOI
Hiroshi Nagai1
TL;DR: In this paper, the effects of mechanical alloying (MA) and grinding (MG) on the preparation processes as well as on the thermoelectric properties of semiconducting β-FeSi 2 were reviewed.
Abstract: Improving effects of mechanical alloying (MA) and grinding (MG) on the preparation processes as well as on the thermoelectric properties of semiconducting β-FeSi 2 were reviewed. MA and MG strongly accelerates the preparation reaction to form β-phase from elemental powders and from the mixture of α-Fe 2 Si 5 and e-FeSi. The electrical resistivity significantly decreased due to the dispersion of fine particles of metallic phase, e.g. e-FeSi phase. As a result, the power factor Q 2 /ρ was significantly improved. Figure of merit Z = Q 2 /ρκ was also improved by MA and MG due to the decrease in the thermal conductivity K. This is due to a decrease in grain size of the β-phase which causes an increase in phonon scattering at the grain boundaries. MA and MG are promissing techniques for the acceleration of β-FeSi 2 formation as well as the improvement of the thermoelectric properties of β-FeSi 2 .

Journal ArticleDOI
TL;DR: In this paper, the gallium and phosphorus content in fully dense, hot pressed compacts was determined by inductively coupled plasma atomic emission spectroscopy, and the transport properties of the compacts were characterized by Hall effect measurements at room temperature and by measurements of electrical resistivity, Seebeck coefficient, and thermal diffusivity to 1000°C.
Abstract: Controlled amounts of GaP and P were added to a Si0.8Ge0.2 matrix by a powder‐metallurgical technique in order to evaluate the optimum composition for thermoelectric applications. Bulk determination of the gallium and phosphorus content in fully dense, hot pressed compacts was performed by inductively coupled plasma atomic emission spectroscopy. The transport properties of the compacts were characterized by Hall effect measurements at room temperature and by measurements of electrical resistivity, Seebeck coefficient, and thermal diffusivity to 1000 °C. Considerable variation in the electrical transport properties were found to accompany changes in the Ga/P ratio, in the total amount of dopant, and changes in other preparation conditions. Alloys with gallium phosphide additions exhibit carrier concentrations higher than those obtained in alloys doped only with phosphorus. Alloys with a nominal phosphorus content greater than 2.0 at. % were found to be overdoped and those containing less than 0.6 at. % pho...

Journal ArticleDOI
TL;DR: In this paper, the Seebeck coefficient and the electric resistivity due to vortex motion were investigated in cuprate superconductors, and a theoretical analysis of the Seeck effect was carried out.
Abstract: In the mixed state of a type II superconductor quasiparticles and magnetic flux quanta respond to a temperature gradient by thermal diffusion, in this way generating the Seebeck and Nernst effects, respectively. Our understanding of the Seebeck effect originates from an extension of the two-fluid counterflow concept, originally introduced by Ginzburg, to the situation where vortices (with a normal core) are imbedded in the superconducting phase. This mechanism results in an intimate connection between the Seebeck coefficient and the electric resistivity due to vortex motion. In all thermal diffusion processes it is the transport entropy of the diffusing species that determines the driving force, and the physics of this quantity is illustrated. Our discussion of the experimental side concentrates on the recent work performed with the cuprate superconductors. The characteristic broadening of the resistive transition in the mixed state, found in these materials due to their high anisotropy and the peculiar vortex structure (pancake vortices), results in a similar broadening of the temperature regime where the Seebeck and Nernst effects appear. In the cuprate superconductors fluctuation effects are highly pronounced because of the large anisotropy, small coherence length, and high critical temperature of these materials. Here the Nernst effect yields particularly useful information since it nearly vanishes in the normal state, and complicated subtraction procedures are unnecessary. As in all transport phenomena, the Hall angle also appears in the thermal diffusion processes, and a summarizing discussion is given. The observation of an unusually large Hall angle for the thermal diffusion of vortices still remains puzzling. A tentative explanation is based on the thermal generation of unbound vortex-antivortex pairs.