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Showing papers on "Thermoelectric effect published in 1994"


Journal ArticleDOI
TL;DR: In this article, a number of properties such as thermal expansion coefficient, sound velocity, thermal conductivity, electrical conductivity and Seebeck coefficient have been measured by hot isostatic pressing of powders.
Abstract: Polycrystalline p‐type samples of IrSb3 and Ir0.5Rh0.5Sb3 have been made by hot isostatic pressing of powders. A number of properties such as thermal expansion coefficient, sound velocity, thermal conductivity, electrical conductivity, Seebeck coefficient, and carrier concentration have been measured. These compounds show promise as thermoelectric materials.

493 citations


Patent
29 Apr 1994
TL;DR: In this paper, a thermoelectric generator is used to convert the heat generated by a semiconductor integrated circuit into electrical energy, which is then used to drive a fan or other airflow generating device.
Abstract: An apparatus and method for recovering power dissipated by a semiconductor integrated circuit includes a thermoelectric generator which converts the heat generated by the integrated circuit into electrical energy. The electrical energy is used to drive a fan or other airflow generating device to cause heated air to be moved away from the integrated circuit and cooler air to be drawn to the integrated circuit to absorb further heat from the integrated circuit. In the described embodiment, the thermoelectric generator is a Peltier cooler positioned between the integrated circuit and a heatsink. The Peltier cooler is operated in the Seebeck mode to generate power in response to the temperature differential between the integrated circuit and the heatsink. The fan is positioned proximate to the heatsink to cause air flow over the heatsink thereby reducing the temperature of the heatsink and thus reducing the temperature of the integrated circuit by causing more heat to be transferred from the integrated circuit to the heatsink.

171 citations


Journal ArticleDOI
10 Feb 1994-EPL
TL;DR: In this article, it was shown that thermoelectric fields transverse to the laser-induced temperature gradient are due to the anisotropy of the thermopower in YBa2Cu3O7-? giving rise to nonzero off-diagonal elements Sij of the Seebeck tensor for films prepared with a tilt angle between the film c-axis and the film surface normal.
Abstract: Signal pulses of several 100 volts and currents of several amperes have been obtained at lateral surface contacts on normal-state YBa2Cu3O7-? films in response to pulsed laser irradiation. The signals are shown to be of thermoelectric origin. Thermoelectric fields transverse to the laser-induced temperature gradient are due to the anisotropy of the thermopower in YBa2Cu3O7-? giving rise to non-zero off-diagonal elements Sij ? of the Seebeck tensor for films prepared with a tilt angle ? between the film c-axis and the film surface normal. Large-tilt-angle films (up to ? = 20?) could be grown on specially cut substrates and may be useful as almost wavelength-independent room temperature radiation detectors.

94 citations


Journal ArticleDOI
TL;DR: In this paper, the thermoelectric properties of mixed oxides at high temperature were investigated in terms of their power factor and Seebeck coefficient, and the results showed that the electrical conductivities of these oxides are significantly high.
Abstract: Thethermoelectric properties of mixed oxides In2O3·MOx(MOx= Cr2O3, Mn2O3, NiO, ZnO, Y2O3, Nb2O5 SnO2) are investigated in terms of the thermoelectric materials at high temperature. The Seebeck coefficients,S, of all the samples have negative values, and those of In2O3·SnO2 and In2O3·ZnO increase linearly with temperature, attaining values of –90 and –210 µV K–1 at 1000 °C, respectively. The electrical conductivities, σ, of these oxides are significantly high. The power factor S2σ of the oxides has constantly positive temperature coefficients up to over 1000 °C. Rather low thermal conductivities, κ, of the sintered bodies of the oxides,ca. 1.7 W m–1 K–1 at room temperature, lead to the largest value of the thermoelectric figure of merit Z= 0.4 × 10–4 K–1 for M = Sn at 1000 °C, and the Z value increases toward higher temperatures.

88 citations


Journal ArticleDOI
TL;DR: In this paper, the possibility of using electrochemical systems for solving the problems of direct thermoelectric conversion is considered for a number of nonconventional electrochemical couples: "inert" electrode/macrocyclic complex with the central coordinated metal ion in different oxidation states (aqueous, aprotic organic electrolyte), ‘inert’ electrode/metal ion (molten salt).

88 citations


Patent
01 Apr 1994
TL;DR: In this article, a configuration of solid state thermoelectric heat transfer or removal elements is provided to enhance the rate and amount of heat removal from electrical and electronic circuit devices.
Abstract: A configuration of solid state thermoelectric heat transfer or removal elements is provided to enhance the rate and amount of heat removal from electrical and electronic circuit devices. By rotating the thermoelectric heat transfer modules ninety degrees and by disposing them between the interdigitated fingers of a cold plate and a heat transfer plate possessing fins, improved thermal transfer is produced without the necessity of liquid coolants or moving part cooling devices. Accordingly, a method and apparatus is provided for enhancing heat transfer using thermoelectric modules. One embodiment of the present invention is particularly seen to be easy to manufacture. Additionally, this embodiment also possesses desirable heat transfer characteristics in terms of the cross sections of thermally conductive components.

85 citations


Patent
21 Nov 1994
TL;DR: A thermoelectric element sheet as discussed by the authors is a set of two layered structures having a plurality of thermal elements which are arranged between insulating films, and electrodes connect the structural units.
Abstract: A thermoelectric element sheet includes at least two layered structures having a plurality of thermoelectric elements which are arranged between insulating films. In each layered structure the thermoelectric semiconductors are arranged in pairs and electrodes connect the thermoelectric semiconductors of each pair to provide a plurality of structural units. Further electrodes connect the structural units. The thermoelectric element sheet can be used in thermoelectric energy conversion systems which depend on the Seebeck, Peltier or Thomson effect to convert thermal energy to electrical energy or vice versa.

75 citations


Patent
05 Aug 1994
TL;DR: In this paper, a thermoelectric apparatus is provided that is compatible with multiple power sources (12) each providing a different voltage, and the control circuitry (16) can sense the voltage provided by the power source (12), and electrically configure the thermoclectric devices (18 and 20) in the assembly between parallel and serial electrical configuration in response to the sensed voltage.
Abstract: A thermoelectric apparatus (10) is provided that is compatible with multiple power sources (12) each providing a different voltage. The present apparatus (10) includes a thermoelectric assembly (14) having a plurality of thermoelectric devices (18 & 20) and control circuitry (16) coupled between the thermoelectric assembly (14) and a power source (12). The control circuitry (16) can sense the voltage provided by the power source (12) and electrically configure the thermoelectric devices (18 & 20) in the thermoelectric assembly (14) between parallel and serial electrical configuration in response to the sensed voltage. The control circuitry (16) also couples the thermoelectric devices (18 & 20) to the power source (12).

72 citations


Journal ArticleDOI
TL;DR: In this paper, the thermoelectric power and thermodynamic properties for various coexisting phase states in Li-Si alloy were determined from electromotive force measurements of the following nonisothermal and isothermal cells, respectively.
Abstract: This paper reports single-electrode Peltier heats for cathodic (or anodic) reactions of Li-Si alloy electrodes in coexisting phase states evaluated from their thermoelectric power values. The thermoelectric power and thermodynamic properties for various coexisting phase states in Li-Si alloy were determined from electromotive force measurements of the following nonisothermal and isothermal cells, respectively, (T) Li I LiCl-KCl I Li-Si (T + ΔT) and (T) Li | LiCl-KCl | Li-Si (T). General methods of estimating the thermoelectric power for a lithium alloy electrode from its thermodynamic properties have been developed thermodynamically. The estimation methods were validated by detailed comparison with experimental results of Li-Si alloy electrode systems.

67 citations


Journal ArticleDOI
TL;DR: In this paper, the efficiency of thermoelectric devices for a superlattice of semiconductor quantum wells was analyzed, and it was shown that the efficiency depends on the property of both layers.
Abstract: The efficiency of thermoelectric devices are analyzed for a superlattice of semiconductor quantum wells. It is assumed that the quantum wells are the thermoelectric active elements, and the layers between conduct only heat. It is shown that the efficiency of the device depends on the property of both layers.

62 citations


Patent
26 Jan 1994
TL;DR: In this article, a thermoelectric module is placed between a first and a second gas conduit to decrease the temperature difference between the temperature of the first and second gas conduits.
Abstract: A heating and cooling apparatus having a first gas conduit, a second gas conduit and at least one thermoelectric module. In a first embodiment, structure is provided to introduce moisture into the second gas conduit, upstream of that conduit's association with the thermoelectric module. The introduction of the moisture into the gas within the second gas conduit functions to decrease the temperature between the temperature of the gas in the first conduit and the temperature of the gas in the second conduit, thereby optimizing the operation of the thermoelectric module. In a second embodiment a plurality of thermoelectric modules are arranged in an array and positioned between the gas conduits and associated therewith. The power supplied to each of the thermoelectric modules is adjusted to correspond to an optimum power input calculated for each thermoelectric module respectively. This calculation utilizes a temperature differential between the temperature of the thermoelectric material at the junction of the thermoelectric module with the first gas conduit and the temperature of the thermoelectric material at the junction of the thermoelectric module with the second gas conduit.

Proceedings ArticleDOI
20 Feb 1994
TL;DR: In this article, a low-cost fiber-in-the-loop (FITL) system with 1.3 µm wavelength was proposed to operate reliably over the temperature range of −40−85°C.
Abstract: Among other factors, the widespread deployment of fiber-in-the-loop (FITL) is hindered by the lack of availability of low- cost laser transmitters that emit at a wavelength of 1.3 μm and operate reliably over the temperature range of −40−85°C. To date, commercial laser transmitters have relied on thermoelectric (TE) coolers to maintain the laser temperature constant against the variations in the ambient temperature because the conventional GaxIn1−xAsyP1−y/InP lasers have shown a strong temperature dependence of threshold current and external quantum efficiency.1,2

Patent
12 Jan 1994
TL;DR: In this paper, a power supply (202) and control system is provided for maintaining the temperature within an enclosed structure using thermoelectric devices (92) to substantially enhance the overall operating efficiency of the refrigerator.
Abstract: Apparatus including a power supply (202) and control system is provided for maintaining the temperature within an enclosed structure (40) using thermoelectric devices (92) The apparatus may be particularly beneficial for use with a refrigerator (20) having superinsulation materials (46) and phase change materials (112) which cooperate with the thermoelectric device (92) to substantially enhance the overall operating efficiency of the refrigerator (20) The electrical power supply (202) and control system allows increasing the maximum power capability of the thermoelectric device (92) in response to increased heat loads within the refrigerator (20) The electrical power supply (202) and control system may also be used to monitor the performance of the cooling system (70) associated with the refrigerator (20)

Patent
23 Nov 1994
TL;DR: In this article, a thermoelectric module for controlling the temperature within an enclosed structure is presented, which consists of a platform, a panel, and a propeller attached to each end of the rotating shaft adjacent to the first heat sink.
Abstract: A module for controlling the temperature within an enclosed structure is provided. The module comprises a thermoelectric assembly, a platform, and a panel. The thermoelectric assembly comprises a thermoelectric device with a first heat sink disposed on one side of the device and a second heat sink disposed on the other side of the device. The thermoelectric assembly further comprises an electric motor attached to one of the heat sinks with a rotating shaft extending longitudinally through the electrical motor and both heat sinks. A propeller may be attached to each end of the rotating shaft adjacent to the first heat sink and the second heat sink respectively. The platform may be removably engaged with the enclosed structure. A first fastener may be used to attach the thermoelectric assembly to the platform. A first opening may be provided in the platform adjacent to one of the propellers. The panel preferably attaches to the platform for use in mounting and sealing the thermoelectric module within the enclosed structure.

Journal ArticleDOI
TL;DR: In this paper, Lanthanum has been substituted for barium in the perovskite type Ba1−xLaxSnO3 solid solutions, and the substitution rate is restricted to a small range of x-values (0 ⩽ x⩽ 0.02), which reveals a scattering of carriers by disorder in metallic type samples (x ⩾ 0.01) and a hopping mechanism in non-metallic ones where the localization seems to be of Anderson type.

Patent
18 Nov 1994
TL;DR: In this paper, a temperature control unit is incorporated directly into the printhead of an ink jet printing system to provide temperature control, which includes a heat pump assembly consisting of at least one thermoelectric device (40, 63, 64), coupled to a heat exchanger (42, 62).
Abstract: A temperature control unit is incorporated directly into the printhead (10) of an ink jet printing system to provide temperature control. The temperature control system includes a heat pump assembly consisting of at least one thermoelectric device (40, 63, 64), coupled to a heat exchanger (42, 62) through which the ink flows. The thermoelectric device (40, 63, 64) conveys heat to or from the heat exchanger (30) carrying the ink depending upon actual ink temperature versus a desired temperature. If the ink is too hot, excess heat is dumped to the heat exchanger (30) (or second heat exchanger (42, 62)) which may be air or liquid cooled. In the event that the ink is too cool, the electrical current to the TED (40, 63, 64) is reversed and heat is pumped to the ink from the heat exchangers (30, 42, 62).

Patent
14 Mar 1994
TL;DR: In this article, 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 the use of a sensor device to monitor the temperature associated with the thermometer.
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 an electrical power source; a rectifying device to provide rectified alternating current from the electrical power source; a comparator device; circuitry for providing a predetermined voltage to the inverting input of the comparator device derived from the rectified alternating current; a sensor device to monitor the temperature associated with the thermoelectric device; circuitry for providing an adjustable DC voltage to the non-inverting input of the comparator; a programmable control device to receive an output from the sensor device and provide an output to the circuitry for providing an adjustable DC voltage; a switching device connected between the thermoelectric device and the rectified alternating current; and control circuitry which is coupled between the switching device and the output of the comparator device and is controlled by the output of the comparator device, the control circuitry activates and deactivates the switching device to apply power to the thermoelectric device when the operating temperature of the thermoelectric device is different than the set point temperature to maintain the thermoelectric device at the set point temperature with minimum variations therefrom. A push-pull transistor configuration is used with the "pulse positioning" power supply allowing bi-polar control of thermoelectric device assemblies.

Patent
04 Nov 1994
TL;DR: In this article, a thermoelectric couple device consisting of a first aluminum oxide base plate, a second aluminum dioxide base plate and a plurality of copper foils between the first and second base plates and alternatively connected in series is presented.
Abstract: A thermoelectric couple device including a thermoelectric couple consisting of a first aluminum oxide base plate, a second aluminum oxide base plate, a plurality of copper foils respectively welded to the first and second aluminum oxide base plates, and a plurality of N type thermoelectric semiconductors, and P type thermoelectric semiconductors respectively welded to the copper foils between the first and second aluminum oxide base plates and alternatively connected in series; and a temperature detecting device mounted on the first aluminum oxide base plate and disposed between the first and second aluminum oxide base plates to detect the inside temperature of the thermoelectric couple.

Patent
28 Jul 1994
TL;DR: In this article, transition metals (T) of Group VIII (Co, Rh, Ir and Sb) have been prepared as semiconductor alloys with Sb having the general formula TSb3.
Abstract: Transition metals (T) of Group VIII (Co, Rh and Ir) have been prepared as semiconductor alloys with Sb having the general formula TSb3. The skutterudite-type crystal lattice structure of these semiconductor alloys and their enhanced thermoelectric properties results in semiconductor materials which may be used in the fabrication of thermoelectric elements to substantially improve the efficiency of the resulting thermoelectric device. Semiconductor alloys having the desired skutterudite-type crystal lattice structure may be prepared in accordance with the present invention by using vertical gradient freeze techniques, liquid-solid phase sintering techniques, low temperature powder sintering and/or hot-pressing. Measurements of electrical and thermal transport properties of selected semiconductor materials prepared in accordance with the present invention, demonstrated high Hall mobilities (up to 8000 cm?2.V-1.s-1?), good Seebeck coefficients (up to 400 νVK-1 between 300C and 700C), and low thermal conductivities (as low as 15 m^_W/cmK). Optimizing the transport properties of semiconductor materials prepared from elemental mixtures Co, Rh, Ir and Sb resulted in a two fold increase in the thermoelectric figure of merit (ZT) at temperatures as high as 400C for thermoelectric elements fabricated from such semiconductor materials.

Patent
29 Aug 1994
TL;DR: In this paper, a thermoelectric element having a very large number of alternating layers of semiconductor material is described, where the alternating layers all have the same crystalline structure.
Abstract: A thermoelectric element having a very large number of alternating layers of semiconductor material. The alternating layers all have the same crystalline structure. The inventors have demonstrated that materials produced in accordance with this invention provide figures of merit more than six times that of prior art thermoelectric materials. A preferred embodiment is a superlattice of Si, as a barrier material, and SiGe, as a conducting material, both of which have the same cubic structure. Another preferred embodiment is a superlattice of B--C alloys, the layers of which would be different stoichiometric forms of B--C but in all cases the crystalline structure would be alpha 0. In a preferred embodiment the layers are grown under conditions as to cause them to be strained at their operating temperature range in order to improve the thermoelectric properties.

Journal ArticleDOI
24 Jul 1994
TL;DR: In this paper, the authors investigated the transport properties of solution-processed conductive polymer blends of polyaniline-(camhpor sulfonic acid), PANI-CSA, with insulating polymethylmethacrylate (PMMA), as a function of various volume fraction (ƒ) of PANI.
Abstract: We investigated the transport properties of solution-processed conductive polymer blends of polyaniline-(camhpor sulfonic acid), PANI-CSA, with insulating polymethylmethacrylate (PMMA), as a function of various volume fraction (ƒ) of PANI-CSA. Due to the phase separated morphology and the fibrillar geometry of percolating objects, a self-assembled PANI-CSA network in insulating matrix shows extremely low percolation threshold (ƒc ≈ 0.003). The characteristic metallic properties of pure PANI-CSA, such as positive temperature coefficient of resistivity at high temperature, linear temperature dependence of thermoelectric power, and frequency independent ac conductivity, are retained in PANI-CSA/PMMA blends down to ƒc. At low temperature, the hopping transports through the conducting polymer network depends on the volume fraction of PANI-CSA in blends and its network structure.

Journal ArticleDOI
TL;DR: The Seebeck coefficient of nine strontium ferrate ceramics with the nominal compositions: SrFeyO3−x (where y=0.909, 0.952, 1, 1.05, 0., 1.10), and NazSr1−zFeO3+x and LazSr 1−z FeO3++x were measured in air from 300-1000°C as mentioned in this paper.

Patent
31 Oct 1994
TL;DR: In this paper, a plurality of interleaved films including a semiductor with suitable doping to establish required extrinsic conductivity and metals having dissimilar lattices such as aluminum and tungsten abutting one another are selected to create Kapitza boundaries between the films such as to reduce thermal conductivity but provide adequate electrical conductivity.
Abstract: A thermoelement (leg) of a thermocouple for use in peltier heating or generation of power by the Seebeck effect including a plurality of interleaved films wherein compositions of neighboring films are selected to create Kapitza boundaries between the films such as to reduce thermal conductivity but provide adequate electrical conductivity. The plurality of interleaved films includes a semiductor with suitable doping to establish required extrinsic conductivity and metals having dissimilar lattices such as aluminum and tungsten abutting one another. The practical number of films in the composite to establish the effect is ten. A preferred thickness of the films is less than twenty thousand Angstroms.

Journal ArticleDOI
TL;DR: The lattice vibrations in LnCoO3 perovskites (Ln = La, Pr, Nd, Sm, Eu, or Gd) have been investigated with reference to the lattice vibration of the ideal cubic perovskiy.

Journal ArticleDOI
TL;DR: In this paper, the parent compound, bismuth telluride, BiaTe3, was synthesized using a simple two-step process for the preparation of fine-particle Bismuth-telluride.
Abstract: With the planned phase-out of chlorofluorocarbon (CFC) refrigerants within this decade, considerable interest has developed in altemative refrigeration and cooling technologies. It is possible that alternatives to CFC liquid-gas expansion systems such as solid-state thermoelectric devices could easily develop into a substantial future technology. Thermoelectric cooling devices based upon the Peltier effect have been used for many years in specialized applications. At present, these units do not achieve the performance currently available with CFCs. Typically, CFC systems operate near 40% of Carnot efficiency while the best thermoelectric systems reach only about 10% of Carnot efficiency.' Nonetheless, a significant thermoelectric cooling industry based on the Peltier effect has already developed. Certain semiconductor materials, particularly bismuth telluride-based alloys, are the materials of choice in modem thermoelectric coolers. These alloys are commonly made through metallurgical melt processing,2 Le., by comelting appropriate amounts of the pure elements in sealed vessels at temperatures above 600 "C, mixing, and then subjecting the melts to controlled cooling. This batch-processing approach is both equipment and labor intensive, while thermoelectric elements cut from the solidified alloys tend to be somewhat fragile. An altemative approach, amenable to automated production, is the fabrication of thermoelectric elements from polycrystalline powder^.^^^ These powders are commonly obtained by crushing the solidified melts and sieving the resultant particulate material. Polycrystalline thermoelectric elements offer improved structural integrity, although they generally exhibit some degradation in thermoelectric performance due to the anisotropic nature of the matieral. As a step toward the development of an altemative route for the preparation of polycrystalline, Bi/Te-based thermoelectric materials, this publication describes a novel synthesis of the parent compound, bismuth telluride, BiaTe3. This method provides a simple, two-step process for the preparation of fineparticle bismuth telluride. The process features the roomtemperature coprecipitation of a bismuth telluride precursor in aqueous media, followed by its conversion to Bi2Te3 through hydrogen reduction. For scale-up to production levels, the coprecipitation reaction lends itself to continuous powder synthesis through the use of a chemical flow r e a ~ t o r . ~ A very recent publication by Groshens et al. describes another approach to the synthesis of Bi2Te3 and related materials by means of elimination reactions conducted in hexane at -30 OC.6

Proceedings ArticleDOI
30 Aug 1994
TL;DR: In this article, the authors used the skutterudite structure TPn3 to obtain room temperature Seebeck coefficient values up to 200 μVK−1 for pn-type and up to −600 μVK −1 for n-type semiconductors.
Abstract: Based on literature data and experimental findings at the Jet Propulsion Laboratory (JPL), semiconductors with the skutterudite structure TPn3 (where T is a transition metal element such as Co, Rh, Ir, Ni, and Pd, and Pn is a pnicogen element such as P, As, and Sb) possess attractive characteristics and show a good potential for high ZT values. The high degree of covalency results in high mobility and low electrical resistivity values while a relatively complex 32 atom unit cell results in a reasonably low thermal conductivity. Both n‐type and p‐type electrical conductivity samples have been obtained. Room temperature Seebeck coefficient values up to 200 μVK−1 for p‐type and up to −600 μVK−1 for n‐type have also been measured on several of these materials. In addition, the large number of isostructural compounds, solid solutions and related phases offer many possibilities for optimization of the transport properties to a specific temperature range of thermoelectric applications. By replacing the transition metal or the pnicogen atom by two of its neighboring elements and ensuring that the number of valence electrons is retained, many ternary phases can be successfully derived from the original CoAs3 skutterudite structure. Some of these materials were found to have substantially lower thermal conductivities compared to those of the binary compounds. The composition, band gap and doping level can be tailored to achieve maximum performance. An overview of the results obtained to date is provided and our approach to achieving high ZT materials are discussed in this paper.

Patent
28 Oct 1994
TL;DR: In this paper, an active intercooler is used to heat or cool a fluid passing through the inter-cooler, where a thermoelectric heat pump is attached to the chamber in order to remove and dissipate heat from the fluid flowing through the chamber.
Abstract: An active intercooler for heating or cooling a fluid passing through the intercooler. The intercooler may be used to cool gases from the compression stage of an engine turbocharger in order to increase engine horsepower. The intercooler could also be used to cool the oil in an engine or transmission. Alternately, the intercooler could be used to heat or cool the air provided to the passenger compartment of a vehicle. The active intercooler includes a chamber through which the fluid flows. A thermoelectric heat pump is attached to the chamber in order to remove and dissipate heat from the fluid flowing through the chamber. A control system is provided to control the current supplied to the thermoelectric heat pump and thus the cooling capacity of the thermoelectric heat pump. A heat sink including a plurality of fins is attached to the thermoelectric heat pump on a surface opposite the chamber in order to increase the ability of the thermoelectric heat pump to dissipate heat.

Journal ArticleDOI
TL;DR: In this article, a mathematical model for calculating the performance of a thermoelectric heat pump to achieve a specific heating load is presented, where the effects of Joulean heating and thermal conduction are considered.

Journal ArticleDOI
TL;DR: The point defects in β-iron disilicide (β-FeSi2) have been investigated by electron paramagnetic resonance (EPR) along with the thermoelectric properties as discussed by the authors.
Abstract: The point defects in β‐iron disilicide (β‐FeSi2) have been investigated by electron paramagnetic resonance (EPR) along with the thermoelectric properties. The samples used are FeSix (1.9≤x≤2.8) ceramics sintered with FeSix micrograins processed in SiH4‐plasma and nonprocessed. EPR detects (1) several S=1/2 signals and (2) a multiplet signal. An S=1/2 signal with orthorhombic g factors (g1=2.061, g2=2.047, g3=2.024) is detected in all n‐type specimens, and ascribed to unpaired electrons of donors associated with iron vacancies. The other S=1/2 signals are detected in both n‐type and p‐type specimens. The centers responsible for these signals are considered to exist in an oxidized intergrain region of the ceramics. The EPR intensity of the multiplet signal due to the closed‐pair of a high spin Fe3+ ion (S=5/2) and an S=1/2 center is reduced by SiH4‐plasma treatments. SiH4‐plasma processing of FeSix micrograins prior to sintering changes the Seebeck coefficient sign and magnitude, depending upon the conditio...

Journal ArticleDOI
TL;DR: In this article, planar thermocouples are designed for investigation of heat transfer in scanning tunneling microscopy and scanning thermal microscopy, and the limit of sensitivity to local thermal power can be as small as 10 nW. The devices are based on two different thin films formed as a cross on a thin glass substrate.
Abstract: Planar thermocouples designed for investigation of heat transfer in scanning tunneling microscopy and scanning thermal microscopy are described. The limit of sensitivity to local thermal power can be as small as 10 nW. The devices are based on two different thin films formed as a cross on a thin glass substrate. Heat fluxes in the cross point can be detected by measuring the thermoelectric signal from two ends of the cross. As described elsewhere planar thermocouples of this type have been successfully used to detect the energy which is deposited by tunneling electrons and to measure the heat which is coupled across a submicron vacuum gap between two metals by the fluctuating fields of electromagnetic surface modes.