Showing papers on "Thermoelectric effect published in 1992"

Preparation and Thermoelectric Properties of Mg 2 Si 1− x Ge x ( x =0.0∼0.4) Solid Solution Semiconductors

Abstract: Mg 2 Si 1-x Ge x Solid Solution Semiconductors were prepared in the composition range 0.0≤x≤0.4. At a composition w=0.4, effects of impurities were investigated for dopants of Sb and Ag. Carrier concentrations were controlled up to 1.5×10 26 electrons/m 3 and 5.5×10 25 holes/m 3 by doping Sb and Ag, respectively. The thermal conductivity κ was measured at 300 K.

Properties of thin film thermoelectric materials: application to sensors using the Seebeck effect

Abstract: The main thermoelectric properties, i.e. Seebeck coefficient α, electrical resistivity ϱ, thermal conductivity K and the coefficient Z of thermoelectric merit, are determined for narrow-gap V2VI3 semiconductors and semimetals. Variations in α, K and ϱ depending on the thickness e of the thin film are also measured. The essential technical characteristics such as the sensitivity S f to flux, the time constant τ and the noise equivalent power of a wide-band radiation detector are modelled according to the adapted thermal conductance eK . The most significant results concerning specific applications are described. Knowledge of these data is useful for the production of sensors based on the Seebeck effect, such as thermocouples, thermopiles, radiation detectors, hyperfrequency power sensors and electrical converters.

Temperature Dependence of Thermoelectric Properties of Mg 2 Si 0.6 Ge 0.4

Abstract: The thermoelectric properties of Sb-doped n-type and Ag-doped p-type Mg 2 Si 0.6 Ge 0.4 samples were investigated in the temperature range 300 to 900 K. The scattering factor r was determined to be 0.0 by measuring the temperature dependence of the Hall mobility. Thermoelectric power and electrical conductivity were measured and discussed on the basis of the degenerated carriers. The thermal conductivity was evaluated from the values measured at 300 K.

Thermoelectric infrared sensors by CMOS technology

Abstract: The authors report two integrated thermoelectric infrared sensors on thin silicon oxide/nitride microstructures realized by industrial CMOS IC technology, followed by one compatible single maskless anisotropic etching step. No additional material is needed to enhance infrared absorption since the passivation layer, as provided by the CMOS process, is sufficient for certain spectral bands. The responsivities are between 12 and 28 V/W. >

Thermoelectric AC power sensor by CMOS technology

Abstract: The authors report the development of a thermoelectric AC power sensor (thermoconverter) realized by industrial CMOS IC technology in combination with postprocessing micromachining. The sensor is based on a polysilicon heating resistor and a polysilicon/aluminum thermopile integrated on an oxide microbridge. The thermopile sensitivity is 9.9 mV/mW and the burn-out power of the sensor is 50 mW. The time constant is 1.85 ms and the SNR (signal-to-noise ratio) is 8*10/sup 9//W. The linearity error with respect to frequency is less than 0.1% below 400 MHz and less than 1% up to 1.2 GHz. >

Electrical-conductivity and seebeck coefficient of (la, ca) (cr, co)o3

Abstract: Electrical conductivity and Seebeck coefficients of (La, Ca) (Cr, Co)O3 were measured as a function of temperature. The electrical conductivity as measured in air from 100 to 1100 °C increased with increasing Co and Ca content. The Seebeck coefficients were positive, indicating p-type conductivity. The substitution of Co for Cr significantly decreased the Seebeck coefficients, indicating that the substitution resulted in an increase in site occupancy, associated with the Co. The additional Ca substitution for La resulted in further decrease in the Seebeck coefficients, then exhibited a temperature-independent behaviour, indicating that the carrier mobility, rather than carrier concentration, was thermally activated. The activation energies were 0.18 and 0.25 eV for LaCrO3 and LaCoO3, respectively, and increased to about 0.50 eV with substitution of 10 mol% Co for Cr and then linearly decreased as Co content increased.

Thermopile differential thermal analysis sensor

Abstract: A differential thermal analysis sensor consisting of two low-impedance differential thermopiles. Each thermopile consists of a series of thermocouples joined in series, with the measuring junctions of the thermocouples arranged around a uniform temperature measuring region, and the thermoelectric reference junctions of the thermocouples arranged around a uniform temperature thermoelectric reference region. The differential thermal analysis sensor can be used for single-sample heat flux differential thermal analysis measurements, dual-sample heat flux differential thermal analysis measurements, or power compensation differential thermal analysis measurements.

Thermoelectric cooling effect in a p-Sb2Te3−n-Bi2Te3 thin film thermocouple

Abstract: Thin film thermoelectric cooling devices based on the Peltier effect are fabricated using a p-Sb2Te3−n-Bi2Te3 thin film thermocouple. The observed values of maximum temperature difference ( ‡T ) between the hot (Th) and cold end (Tc) for a single-stage device is about 13 K, whereas that for a two-stage cascade arrangement is about 19 K. The figure of merit of these thermocouples is calculated and the implications are discussed.

Studies on the seebeck effect in semiconducting ZnO thin films

Abstract: For ZnO thin films prepared by a pyrolytic technique, the thermoelectric power has been measured from room temperature up to 200 °C with reference to pure lead. The thickness and temperature dependence of its related parameters have been studied. The Fermi levels were determined using a nondegenerate semiconducting model. The carrier scattering index, activation energy and temperature coefficient of activation energy, have all been obtained at different ranges of thickness and temperature. All the samples were polycrystalline in structure and optically transparent.

Switchable thermoelectric element and array

Abstract: A thermoelectric array, such as a thermocouple array, includes a pair of dissimilar conductors disposed adjacent to each other at a plurality of locations. A switch is provided which selectively electrically couples and decouples the conductors at each such location, and an effective thermoelectric element is formed at the location where a switch is closed. The switches may be easily controlled to ensure that only the switch at the desired location is closed to form an effective thermoelectric element. Switches may include MOSFET pairs in series or dual-gate MOSFETs, and arrays of such switched thermoelectric elements may be integrated and fabricated on a common semiconductor substrate.

Thermal conductivity of thermoelectric Si(0.8)-Ge(0.2) alloys

Abstract: The thermal conductivity of heavily doped, n-type Si-Ge alloys has been studied from 300 to 1200 K. The scattering rate of several phonon scattering mechanisms has been calculated, including intrinsic scattering, mass defect and distortion scattering, phonon-electron scattering, and scattering by inclusions. These rates were then used to calculate the lattice thermal conductivity. The electronic component of the thermal conductivity was calculated from the calculated Lorenz ratio and measured values of the electrical conductivity. The total thermal conductivity was then compared to measured values for a specimen studied by Vining et al. (1991).

Method and apparatus for the thermoelectric generation of electricity

Abstract: A thermoelectric generator includes a plurality of thermoelectric junctions embedded in each of a pair of thermally conductive and electrically non-conductive layers, these layers being separated by a thermally and electrically non-conductive layer. The junctions are connected to form a thermopile. An absorbent layer is provided adjacent one of the thermally conductive layers. A liquid such as water is applied to the absorbent layer, so that evaporation of the liquid from the absorbent layer enhances the temperature differential between the two thermally conductive layers.

Anomalous photovoltaic response in YBa2Cu3O7.

Abstract: Several experiments were carried out to study the origin of the anomalous photovoltaic effect in high-quality YBa 2 Cu 3 O 7 thin films In particular, the issue of whether the signal is induced by thermal gradients was addressed Using samples with well-characterized orientation and texture, and using low-power cw lasers, it was determined that the signal was proportional to the thermal gradient along the c axis However the magnitude of the signal was more than 10 times larger than that produced by thermoelectric power

Measurements on the thermoelectric properties of thin layers of two metals in electrical contact. Application for designing new heat-flow sensors

Abstract: The authors describe the operation of new thermopiles in the form of bimetallic printed circuits comprising numerous electrodes electroplated on a continuous foil of lower conductivity. When a temperature gradient is applied in the direction parallel to the plane of lamination, such a device behaves like a thin-film thermoelectric element. In the more general case, where a heat flow tube is passed in the direction normal to the plane of lamination, the amount of EMF generated in the continuous support is determined by all the axial temperature gradients distributed in the double-layer thickness. As an application, the authors present new heat-flow sensors which are directly responsive to the asymmetry of a fringing flow pattern induced by a normal heat flow to be measured.

The Effect of Atmosphere and Doping on Electrical Conductivity of CuO

Abstract: The electrical conductivity and Seebeck coefficient have been measured for pure and Li- or Al-doped CuO. The sign of the Seebeck coefficient of all samples shows p-type semiconducting properties in all temperature and oxygen partial pressure ranges employed in this measurement. The temperature dependence of electrical conductivity shows two regions. The conductivity in the high-temperature region is independent of the doping and the atmosphere, whereas that in the low-temperature region depends strongly on such factors.

Cryo-therapy system for small areal freezing of surfaces esp. for skin alterations - has cold probe and heat exchanger which are connected heat-conducting with each other by Peltier elements having heat contact surfaces

Abstract: At least one Peltier element (36;46) with its associated heat contact surface (38) is respectively fixed heat-conducting at opposite lying main surfaces (34) of the heat exchanger (14). The cold probe (12) is arranged axially aligned with the heat exchanger (14). Another pair of Peltier elements (46) with associated heat contact surface (48), is respectively arranged heat-conducting at opposite lying main surfaces (50) of the cold probe (12). The Peltier elements (46) of the cold probe with their second heat contact surfaces (44) distant from the first heat contact surfaces (48), are connected heat-conducting with the second heat contact surfaces (40) of the Peltier element (36) of the heat exchanger, distant from the first heat contact surfaces (38). ADVANTAGE - System has comparatively small vol. It is easy to manipulate and has relatively high thermal efficiency.

Heater mechanism including a light compact thermoelectric converter

Abstract: A heater mechanism incorporating a thermoelectric converter for use with a self-powered, solid, liquid or gaseous fueled, heater. During operation of the heater mechanism the thermoelectric converter supplies sufficient electrical power to (a) sustain the heater in operation, (b) maintain the starter battery at full charge, and (c) provide auxiliary power to remove and transport heat to desired locations away from the heater. The converter is a highly compact design (high power output per unit volume of space) and lends itself to high volume (mass production) and automated assembly techniques to produce it inexpensively. The thermoelectric converter is made of fewer components than prior art devices. A number of components in the thermoelectric stack serve dual or even multi-functions. The thermoelectric stack components are bonded or mounted together in such a manner as to permit handling as a unit.

Thermoelectric cooling device

Abstract: A thermoelectric semiconductor element is disclosed which is particularly low in toxicity and inexpensive. The element is mainly composed of a complex oxide comprising strontium and titanium. An oxide semiconductor possessing oxygen deficiency is used as the n-type element. According to the invention, as compared with a thermoelectric semiconductor element for thermoelectric cooling using a conventional Bi-Te thermoelectric semiconductor which is particularly toxic due to addition of Se or the like, the toxicity of the n-type semiconductor element part is lowered, and a thermoelectric semiconductor element excellent in performance is obtained.

Thermoelectric properties of fine grained (75% Sb2Te3-25% Bi2Te3)p-type and (90% Bi2Te3-5% Sb2Te3-5% Sb2Se3)n-type alloys

Abstract: The thermoelectric properties of fine-grained alloys prepared by either cold pressing and sintering or hot pressing in the range 5–50 μm are compared with single-crystal best-direction values. It is shown that for thep-type alloy, almost the entire thermoelectric properties are recovered, i.e. the figure of merit for the finest grain size is almost the same as the best single-crystal value. The same trend is observed in then-type alloy except that 90% of the single-crystal figure of merit is recovered. These results are discussed in terms of a model which suggests that degradation of favourable thermoelectric properties by powdering the alloys is compensated by (1) decrease of thermal conductivity due to scattering of phonons at grain boundaries for grain sizes that are comparable to the mean free path of phonons; and (2) retention of some of the anisotropic properties of the single crystal in the fine-grained compacts.

Dynamic study of conduction carriers in YBa2Cu3O7- delta thin films using a pulsed-laser-induced transient-thermoelectric-effect method.

Abstract: The pulsed-laser-induced transient thermoelectric effect (TTE) has been measured for c-axis-oriented YBa 2 Cu 3 O 7-δ thin films over a wide time range (50 ns to 2 ms) and temperature range (10-300 K). The analysis of the decay curves of TTE voltages has revealed that the YBa 2 Cu 3 O 7-δ system has multiple conduction carriers, the semiconducting holes in the one-dimensional (1D) CuO chains and two types of holes (light-mass and heavy-mass holes) arising from the metallic 2D CuO 2 -derived band

The thermoelectric effect in a semiconductor superlattice in a non-quantized electric field

Abstract: The thermoelectric effect in a semiconductor superlattice in a nonquantized electric field is investigated for electrons of the lowest miniband in the linear approximation of Del T. Analytical expressions for the thermopower and the heat conductivity coefficient are obtained as functions of the superlattice parameters Delta and d, temperature, concentration and electric field E. The results confirm the fact that depending on the relation between Delta and other characteristic energies of the carrier charge (kT, xi and h(cross)/ tau ) the carrier charges can behave either as a quasi-two-dimensional or as a three-dimensional electron gas. The prospect of using a superlattice as a good-quality and highly efficient thermoelement is also proposed.

Processes for producing a thermoelectric material and a thermoelectric element

Abstract: A process for producing a thermoelectric material comprises molding a material powder comprising two or more elements selected from the group consisting of bismuth, tellurium, antimony and selenium and having average diameter in the range from 0.05 to 100 μm and sintering the molded material powder with or without hot isostatic pressing. The material powder may be calcinated before the molding. A process for producing a thermoelectric element comprises cutting out pieces of a pillar-like shape from each of a p-type thermoelectric material and a n-type thermoelectric material, connecting the pieces cut out from the p-type thermoelectric material and the pieces cut out from the n-type thermoelectric material alternately with electrodes at the upper faces or the lower faces of the pieces and attaching insulating base plates to the surfaces of the electrodes. The p-type thermoelectric material and the n-type thermoelectric material are respectively produced by the process described above. The thermoelectric element has improved thermoelectric property, excellent stability of the thermoelectric property and excellent mechanical strength.

Thermoelectric field emission cathode

Abstract: PURPOSE:To provide a practically useful thermoelectric field emission cathode whose emission angle current density is high but whose total emission current is not so high by providing a specific W single crystal acicular electrode with a cover layer made from Zr and O, and limiting the radius of curvature of the tip of the electrode. CONSTITUTION:In a thermoelectric field emission cathode provided with a cover layer of crystal orientation, the tip of its acicular electrode 1 has a radius (r) of curvature of 0.2 to 0.4mum. The electron emission characteristic of the thermoelectric field emission cathode is determined by intricate factors including the surface configruation, condition, temperature, and field intensity, etc., of the tip of the acicular electrode from which electrons are emitted. The radius (r) of curvature of the tip of the cathode is made smaller than 0.4mum so that higher emission angle current density now required can be obtained. Provided the radius of curvature of the tip of the cathode is in a range as high as 0.2mum and more, the need for a device of a particularly large capacity is eliminated. The thermoelectric field emission cathode is useful for an electron microscope, an electron beam exposing equipment and an electron beam tester, etc., all of which require an electron beam of high intensity.

Thermoelectric air conditioner with absorbent heat exchanger surfaces

Abstract: Corrugated fins are provided at opposing sides of a corrugated thermoelectric device constituting a thermoelectric circuit. This air conditioner is obtained by superposing a plurality of the thermoelectric devices. When a current is fed to the thermoelectric devices, heat is absorbed from one of two fluids running through the corrugated fins and discharged to the other fluid, so as to define a heat pump cycle is defined. The thermoelectric devices are superposed so that the confronting surfaces of the neighboring thermoelectric devices constitute a heat radiation surface respectively and a cooling surface. The corrugated fins intersect with each other, so that the two fluids are prevented from mingling and are allowed to flow in and out of different surfaces.

A quick thermoelectric technique for typing HgCdTe at liquid nitrogen temperature

Abstract: A simple and quick technique based on thermoelectric effect of semiconductors has been developed for screening the conductivity type of narrow band‐gap HgCdTe materials. This technique generates a temperature gradient across the sample by partly dipping it in liquid nitrogen. The induced Seebeck voltage is then measured by loading two spring contact probes to two separate points on the sample below and above the liquid nitrogen level. It was found, as expected by the theory, that the thermoelectric measurements on p‐type HgCdTe are much less influenced by the inverted surface effects than Hall measurements.

Thin-film transparent thermocouples☆

Abstract: Transparent thin-film electrical conductors have been sputter deposited to form transparent thermocouples Indium-tin oxide (ITO) and antimony-tin oxide (ATO) have demonstrated Seebeck coefficients of 7–77 μV/°C, depending on their conductivity and fabrication parameters In addition to results for in-house-fabricated thermocouples, thermoelectric measurements are reported on commercial ATO, ITO, and fluorine-doped tin oxide transparent films