Showing papers on "Thermoelectric effect published in 1983"

Thermoelectric Determination of Cation Distributions in

Abstract: Thermoelectric coefficient measurements in the system Fe3O4-Fe2TiO4 were used to determine the cation distributions from 600° to 1300°C. The cation distributions obeyed the relation -RT In K=-9.61+2(-0.0154T)b+0.0256T (kJ/mol) where KFecd is the iron distribution constant and b is the tetrahedral Fe3+ concentration. Low-temperature extrapolations agreed with experimental magnetometry and lattice parameter results. With the incorporation of a subregular size-mismatch term, agreement with high-temperature thermodynamic data was achieved. A solvus at intermediate temperatures was correctly predicted by the model.

Measurement and Interpretation of Thermopower in Oxides

Abstract: The influence of point-defect gradients on thermoelectric coefficient measurements in oxides is quantified. This permits corrections to be made for data collected by conventional means and suggests alternative techniques of thermopower measurements which maintain the average sample temperature while imposing thermal gradients. Experimental results on CoO, Fe/sub 3/O/sub 4/, and FeO in equilibrium with various atmospheres are considered.

Thermoelectric generating system

Abstract: A thermoelectric electricity generating system for connection with a heat source and a heat acceptor respectively by first and second elongate plates of substantially constant cross section and high heat and electrical conductivity. A plurality of flat platelike thermoelectric members engage and are firmly sandwiched between the first and second plates. Thin surface layers of low electrical conductivity, but high heat transfer capability across the thickness thereof, are interposed between the thermoelectric members and first and second plates. The first plate may connect with a heat source by fitting in an opening in the wall of a fuel fired heater, to thereby apply a temperature drop across the thermoelectric members and thereby generate electricity.

Semiconductor laser module having an improved temperature control arrangement

Abstract: A semiconductor laser device is provided including semiconductor laser element, a PN-junction element which is used for temperature detection, and a thermoelectric heat pump which is electrically connected to the PN-junction element. According to this arrangement, heat developing from the semiconductor laser element is sensed by exploiting the fact that the forward voltage V F of the PN-junction element or PN-junction diode changes in correspondence with the change of the ambient temperature (this phenomenon itself is a matter already known), and the change of the forward voltage V F is fed back to the thermoelectric heat pump. Therefore, even when the semiconductor laser device is placed in the condition of a very high ambient temperature (open air temperature), the semiconductor laser element is cooled down to a predetermined temperature by the thermoelectric heat pump so as to produce a prescribed optical power at all times. Thus, the semiconductor laser element itself is driven in an appropriate temperature condition (for example, 25° C.), so that the degradation of the semiconductor laser element can be prevented.

Thermoelectric infrared detector array

Abstract: The detecting element of a thermoelectric infrared detector consists of p-n junctions of a thermopile which are located on a thin layer of unsupported silicon dioxide. The silicon dioxide spans an opening which extends through a silicon semiconductor substrate. The reference junctions of the thermopile are located above the silicon substrate. The detecting p-n junctions on the thin silicon dioxide above the opening in the substrate have a low heat capacity and respond rapidly to temperature changes, whereas the reference junctions above the thick substrate have a much higher heat capacity and tend to maintain their ambient temperature. The conduction of heat between the detecting p-n junctions and the reference junctions is limited by the thin insulating layer of silicon dioxide which joins the detecting p-n junctions to the substrate under the reference junctions.

Thermoelectrically regulated sample holder for Raman spectroscopy

Abstract: An easily built thermostated sample cell holder for Raman spectroscopy is described. The apparatus, which uses thermoelectric heat pumps as heating and cooling elements, is characterized by a fast response and a temperature stability at the sample of better than ±0.1 °C over the −20° to 100 °C temperature range. The desired temperature can be either selected manually or controlled by computer.

Micromechanical thermoelectric sensor element

Abstract: A thermoelectric sensor element that is adapted to respond to thermal radiation is capable of manufacture into a sensor array on a single crystal semiconductor means, such as silicon. An anisotropically etched pit is provided under the sensing surface, and the pit generally corresponds to the geometry of the sensor element. The geometry is selected to be rectangular and falls along a selected orientation of the particular crystalline structure used for manufacture of the device to thereby allow for a high density of the sensor elements. The sensor elements are manufactured of two dissimilar metals in a sinuous pattern to provide the thermoelectric effect.

Thermoelectric device and method of making and using same

Abstract: An invention is disclosed which provides improved thermoelectric devices and methods of making and using the same. The device exhibits enhanced efficiency and operating life through the use of a bonding material comprising at least 75% busmuth together with an adherent metallic layer interposed between the boundary structure and correspondary thermoelectric semiconductor element.

Size and temperature effects on thermoelectric power of β‐tin thin films

Abstract: Tin thin films of thicknesses in the range 500–7000 A have been prepared by vacuum deposition at room temperature at a pressure of 5×10−5 Torr on glass substrates. Thermal electromotive forces (emfs) of these films have been measured after aging as a function of temperature difference. It is found that the thermoelectric power of the films is independent of temperature in the range studied (300–425 °K). It is also found that the thermoelectric power of the films obeys the inverse thickness dependence predicted by size effect theories. The electronic mean free path is evaluated to be 530 A.

Controlled power converter for thermoelectric heat pump drive

Abstract: A controlled power conversion system for providing power to a thermoelectric heat pump for controlling the temperature of a device, such as a chilled mirror used in a chilled mirror humidity sensor. The system uses means, responsive to a DC input power source and to a control signal representing changes in the temperature of the device, for providing periodic pulses of the DC input power having a duty cycle which is controllable in accordance with the control signal. The input power is time-averaged and an energy storage means, responsive to the periodic pulses of DC input power, is utilized to provide a controllable time averaged DC power output to the heat pump.

Thermoelectric devices having improved elements and element interconnects and method of making same

Abstract: A new and improved thermoelectric device and a method of manufacturing same takes advantage of the anisotropy of the materials employed to provide a substantially increased power output over prior art devices. The individual thermoelectric elements are pressed using techniques such as those employed in powdered metallurgy and electrically coupled such that a current path is established through the elements in a direction substantially perpendicular to the direction of pressing. The method and device of the present invention also achieve a substantially thinner device than was previously possible with no concomitant sacrifice in individual thermoelectric element integrity or increased resistance of the electrical connections between the individual thermoelectric elements. The individual thermoelectric elements are dimensioned such that each has a first dimension substantially greater than either its second or third dimensions. The individual elements are then electrically connected to one another in series along their first, greater dimensions so that the relationship between the length, cross-sectional area and resistivity of the electrical connections can be optimized.

Substrateless thermoelectric device and method of making same

Abstract: A new and improved thermoelectric device of the type which provides electrical energy in response to a temperature gradient applied across the device exhibits both structural integrity and improved efficiency. The new thermoelectric device includes a plurality of thermoelectric elements, coupling means on opposite respective sides of the thermoelectric elements for interconnecting the elements electrically in accordance with a predetermined pattern, and encapsulant means including an encapsulant material covering the exposed surfaces of the thermoelectric elements. The encapsulant forms void spaces between the elements for providing effective thermal insulation between the elements and confining substantially all of the heat flow from the temperature gradient to through the elements. The coupling means includes electrically conductive plate segments for electrically interconnecting the thermoelectric elements. The plate segments are joined to the elements on respective opposite sides thereof and are contacted and held in fixed relative relation by the encapsulant material. The plate segments further define an outer periphery of the device and the encapsulant material bridge across the plate segments at the periphery of the device. As a result, structural device integrity is obtained while more efficient use of the temperature gradient is made.

Thermoelectric actuator for mirror adjustment

Abstract: A thermoelectric apparatus for adjusting the shape or position of a mirrory application of pressure from a device which changes dimensionally with changes in temperature. The device is a metallic or non-metallic generally tubular member having a heat pump mounted thereon which in turn has a thermal connection to a controllable heat source. A temperature sensor is also mounted on the device and both the temperature sensor and the heat pump are electrically connected to a controller.

Anomalous temperature dependence of thermoelectric power of PbTe thin films

Abstract: PbTe thin films of thicknesses ranging from 400 to 4000 A have been prepared by vacuum evaporation at a pressure of 5×10−5 Torr on clean glass substrates held at room temperature. The thermoelectromotive force of these films has been measured in the temperature range 300–600 K. It is found that thermoelectric power, SF varies anomalously with temperature, being constant at lower temperatures, and rapidly decreasing at higher temperatures. SF is found to be positive indicating that the samples are p type. The anomalous behavior is explained by assuming that at higher temperatures additional donor levels are generated due to creation and ionization of defects in the system.

Multi-element thermoelectric non-destructive testing device and method

Abstract: A non-destructive testing device and method in which information is obtained from a plurality of thermoelectric junctions made between an unknown material and a plurality of test elements of different known characteristics to provide data for identifying the unknown material.

Thermoelectric power of aluminum films

Abstract: The thermoelectric power (TEP) of aluminum film was measured in the thickness range of 300–1600 A. From the size effect of electron diffusion term, the energy dependence of the mean free path of conduction electrons (U) and the Fermi surface area (V) were calculated to be U=0.957 and V=1.322. The phonon‐drag part of TEP also exhibited a size effect from which the mean free path of the dominant phonon mode was estimated to be 400 A. The effect of grain boundary scattering on thermoelectric power was also studied.

Thermoelectric device and manufacture thereof

Abstract: A thermoelectric device includes first and second sets of spaced apart copper plate segments. Thermoelectric elements which generate electricity are disposed between the sets of copper plate segments. The elements are electrically and thermally fastened thereto by a solder paste screen printed on the inner surfaces of the sets of copper plate segments. A ceramic potting compound which absorbs thermal expansion of the device fills the voids between the thermoelectric elements and the copper plate segments and a thick film ceramic insulator coats the outer surfaces of the sets of copper plate segments. Also disclosed is a method for manufacturing the device of the present invention.

Cation distribution of the system Zn 1-x Co x FeMnO 4 by x-ray, electrical conductivity and Mossbauer studies

Abstract: Structural, electrical and Mossbauer studies were carried out for the system Zn1−xCo x Fe MnO4. It is observed that forx⩽0.6, the ionic configuration of the system is Zn 1− 2+ Mn 2+ [Co 3+ Mn 1− 3+ Fe3+]O 4 2− and forx⩾0.8 Fe3+ ions occupy tetrahedral site also. On the basis of electrical and Mossbauer studies a probable valence distribution of CoMnFeO4 has been suggested. All the compounds showed positive values of thermoelectric coefficient and electrical conduction takes place by a hopping mechanism. Activation energy and thermoelectric coefficient values decreased with decrease in concentration of Zn2+ ions. The compounds possess low mobility values varying between 10−7 and 10−9 cm2/V sec.

Development of New Materials by Ionized-Cluster Beam Technique

Abstract: In the Ionized-Cluster Beam (ICB) technique, deposition by macroaggregates consisting of 500 to 2000 atoms loosely coupled together involves low ratios of charge to mass. Consequently, high mass density beams at low equivalent energy per atom in an optimum range for film formation can be transported without problems due to space charge repulsion forces and deposition onto insulating substrates is easily possible due to low accumulation of ion charge. The presence of ionic charge has great influence upon film formation mechanisms in spite of low content of ions in the total flux. Also, because of the kinetics of cluster breakup upon impact, enhancement of migration of adatoms upon a substrate surface can be achieved by increasing the acceleration voltage. It is possible to control the mechanical, crystallographic, optical and magnetic properties of films over three dimensions by variation of acceleration voltage or ion content in the total flux. Films of many materials have been formed at low temperatures with well-controlled characteristics. Among examples of interest are included metal and semiconductor material films for functional devices and VLSI applications, intermetallic compound films for magnetic or thermoelectric uses and organic material films. Results suggest that ICB offers exceptional potential for applications involving formation of new materials.