Showing papers on "Thermoelectric effect published in 1969"

The thermoelectric powers of transition metals at high temperature

Abstract: This paper is concerned with a survey of the experimental data for the thermoelectric power† The thermoelectric power is hereinafter referred to as TEP of transition metals and with their discussion. For the first time a critical review of the main data, which are given in the literature and proved to be rather incomplete, is presented. When necessary, the author has conducted the TEP measurements within the temperature range of 80° to 1800°k, wherever it was possible. For the first time TEP data have been obtained for scandium, osmium and, effectively, for hafnium; erroneous data for thorium and ruthenium have been corrected; the temperature measuring range for many other metals has been substantially extended. Finally, from the data found in the literature and the new results, a fairly complete notion has been formed of the high-temperature behaviour of TEP for all transition metals (except technetium) in the 3d, 4d, and 5d series of the periodic system, as well as for uranium and thorium. Some...

Electrical conductivity and thermoelectric power of the molten Tl + Se and Tl + Te systems

Abstract: The electrical conductivity and thermoelectric power of the liquid T1 + Se and T1 + Te systems have been measured as a function of concentration and temperature. Both of the systems show a deep minimum in the electrical conductivity at the composition corresponding to T12Se and T12Te. The absolute thermoelectric power changes its sign around this composition, being negative for the T1-rich solutions and positive for the Se- and Te-rich solutions. The impurity effect was examined in the T12Se melt. The electrical conductivity of the saturation range, where the carrier density can be considered to be constant, is discussed in the light of the scattering model.

Temperature controlled centrifuge

Abstract: Peltier effect thermoelectric devices are mounted in a rotatable centrifuge head. Thermal conduction paths are attached between the thermoelectric devices and a position adjacent to the specimen being rotated in the centrifuge. A temperaturecontrolled device responds to the difference between a preselected temperature and the temperature of the specimen for maintaining the fluid at the preselected temperature.

Some electrical transport studies on compounds of the Tl-Te system

Abstract: Galvanomagnetic, thermoelectric and electrical conductivity measurements were made on single crystal specimens of Tl2Te3, TlTe and γ-phase in the temperature range from 77° K up to 500 to 700° K. All crystals were found to be of p-type conductivity. Measurements of the electrical conductivity versus composition have revealed that γ-phase represents solid solutions of Tl and Te in the compound with formula Tl5Te3. Also, it has been found that both TlTe and γ-phase samples exhibit a metallic behaviour in contrast to Tl2Te3, which has semiconducting properties. In the intrinsic conduction region a thermal energy gap of a 0.68 ± 0.03 eV was found, which was compared with that obtained from optical transmission measurements. The electrical properties of Tl-Te compounds are discussed on the basis of the general valence rule.

Thermal electric dental pulp tester

Abstract: A thermoelectric probe for applying heat or cold to a localized area of a body for medical treatment comprising a thermoelectric module mounted in thermal conductive contact with a heat transfer unit including a honeycomblike assembly for maximizing conduction of heat from the module, and a heat exchange system including a pair of concentric tubular units connected to one side of the honeycomblike unit. One of the tubular units is coupled at its remaining end to an air suction pump for drawing ambient air through the honeycomblike unit.

Fabrication of thermoelectric elements

Abstract: An isostatic hot compressing process step is employed to exert a pressure of from 5,000 p.s.i. to 50,000 p.s.i. on the exterior surfaces only of a hollow cylindrical thermoelectric element having thermoelectric material disposed between exterior and interior cylindrical shell members to plastically deform the exterior surfaces of the element and reducing the annular crosssectional area of the element from 1 percent to 15 percent to provide at least an intimate physical contact between the body of thermoelectric material contained therein and the inner and outer members of the element. The inner member of the element is in compression after the hot isostatic compression is removed. Isostatic cold compressing may be applied to the element prior to the isostatic hot compressing process step.

The thermoelectric properties of heavily doped hot-pressed germanium-silicon alloys

Abstract: The electrical resistivity and Seebeck coefficient have been measured on a series of hot-pressed Ge-Si alloys over the temperature range 300-1200 °K and Hall mobility in the range 300-1000 °K. The results indicate that some specimens possess mobilities and Seebeck coefficients close to single-crystal values. Making use of available thermal resistivity data the maximum efficiency of a single couple generating device constructed from the best p-type and n-type alloys was computed to be 8% when operating between 300-1000 °K.

Thermoelectric Power of Vacuum‐Evaporated Au–Ni Thin‐Film Thermocouples

Abstract: Continued investigations of the thermoelectric properties of Au–Ni thin‐film thermocouples have been made. The thickness dependence of the Seebeck coefficient for Ni films of variable thickness on bulk Au was determined and found to be sensitive to the thermal history of the thin film thermocouples. By developing suitable preparation techniques for these thermocouples, involving several periods of annealing, time‐invariant calibration curves were obtained. The thickness dependence of the Seebeck coefficient was found to follow closely the predictions of the size‐effect theory of Mayer.

Thermally cascaded thermoelectric generator

Abstract: A THERMALL CASCADED THERMOELECTRIC GENERATOR IS DISCLOSED. THE GNENERATOR INCLUDES A FIRST STAGE CONTAINING HIGHTEMPERATURE THERMOELECTRIC ELEMENTS AND A SECOND STAGE CONTAINING LOWER TEMPERATURE THERMOELECTRIC ELEMENTS. THE STAGES ARE CONNECTED IN THERMAL SERIES BY MEANS OF AN ELONGATED HEAT TRANSFER PIPE CONTAINING A LIQUID METAL AND A WICK. A PORTION OF THE HEAT RADIATED TO THE FIRST STAGE FROM A HIGH-TEMPERATURE RADIOISOTOPE SOURCE IS CONVERTED TO ELECTRICITY. THE HEAT REJECTED BY THE FIRST STAGE IS CONDUCTED TO THE HEAT PIPE AND ABSORBED BY THE LIQUID METAL AS LATENT HEAT OF VAPORIZATION. THE VAPOR RISED TO THE SECOND STAGE AND CONDENSES TO GIVE UP LATENT HEAT OF CONDENSATION WHICH IS TRANSFERRED TO THE SECOND STAGE AND IS CONVERTED TO ELECTRICITY THEREIN. THE CONDENSED LIQUID RETURNS ON THE WICK TO THE VICINITY OF THE FIRST STAGE.

The electric polarization induced by temperature gradient and associated thermoelectric effects

Abstract: It is shown that the possible existence of a direct effect, which consists in the production of electric polarization in a temperature gradient, is connected with the existence of effects that are analogous to the known thermoelectric effects. The thermoelectric effects under study play a role in a periodic regime of temperature and electric current.

Direct heat rejection path radioisotopic thermoelectric generator

Abstract: Compression springs on the hot side, bias the thermoelectric elements of the radioisotopic powered thermo-electric generator into contact with the casing wall. The bus straps, which electrically connect the cold ends of the thermoelectric elements are bonded directly to the inner wall of the casing by a pressure sensitive epoxy adhesive which is preferably a dielectric but a good thermal conductor thereby eliminating the need for cold-end hardware.

Errors in thermoelectric thermometers

Abstract: Hitherto, no quantitative relationship between errors in thermoelectric thermometers and their causes (i.e. changes in Seebeck coefficient and temperature distribution) has been demonstrated. A theory of the operation of thermocouples has therefore been developed. From this, an experimental method is derived, which distinguishes and measures the effect of various factors on a given type of thermocouple, and which enables the results to be used to calculate the performance of the thermocouple under given conditions. The effects of as-received inhomogeneity, plastic strain and heating up to 650°C are given for chromel-alumel, and in less detail for other common materials. It is shown that it is possible to predict drift and other instabilities in chromel-alumel under defined conditions, and reduce the uncertainty of measurements by an order of magnitude in favourable cases. It is also shown that the conventional concepts of calibration which are widely used in the application and investigation of the performance of thermocouples, are generally fallacious.

Direct-current generator for superconducting circuits

Abstract: A DC generator for a superconducting circuit includes a thermoelectric material member with superconductors connected across the member and the superconducting circuit. A heater attached to one end of the thermoelectric member creates a potential gradient along the member while the member is subject to an environmental temperature which maintains the superconductors in a superconducting state.

Thermomagnetic Effects in Bismuth. I. Thermoelectric Power

Abstract: Theoretical interpretation of an anomalous behavior of the thermoelectric effect in bismuth is presented. According to Farag and Tanuma, the thermoelectric power has sharp minimum at low temperatur...

Thermoelectric cooling devices

Abstract: : The book is dedicated to one of the youngest but rapidly developing fields of contemporary refrigeration engineering--that of thermoelectric cooling. The physical nature of thermoelectric cooling is set forth in an accessible format, with design and construction methods for thermoelectric cooling devices intended for various purposes. Various thermoelectric cooling devices are described which are intended for use in scientific practice and engineering. A large section of the book is devoted to the utilization of thermoelectric cooling in medicine.

Aluminum for bonding Si-Ge alloys to graphite

Abstract: Improved thermoelectric device and process, comprising the high-temperature, vacuum bonding of a graphite contact and silicon-germanium thermoelectric element by the use of a low void, aluminum, metallurgical shim with low electrical resistance sandwiched therebetween.

Thermoelecric Effect in Semiconducting Barium Titanate

Abstract: Thermoelectric measurements were carried out on polycrystalline semiconducting barium titanate systems. Doping elements used were erbium and terbium. The ambient temperature of the samples was varied from room temperature to 200°C. It was found that the thermoelectric power changes its sign beyond the transition temperature and becomes positive, even though the carrier concentration remains constant. A possible mechanism based on the idea of electron-phonon Umklapp process has been suggested to explain this reversal of sign.

Seebeck Effect in α‐Nb2O5 Near Stoichiometry

Abstract: The Seebeck coefficient, thermoelectric power Q, was measured in ceramic α‐Nb2O5 with respect to platinum over a range of temperature of 700°–1400°C and a range of ambient oxygen partial pressure of 1.0−10−5 atm. The data are interpreted on the basis of electrons moving in a narrow conduction band.

Instrument for measuring the net flux of radiant energy through a plane

Abstract: A pair of solar radiation-absorbing surfaces mounted on opposite sides of a probe utilize the Seebeck and Peltier effects to maintain equal surface temperatures thereby avoiding errors due to wind. The current produced by the effects is a measure of the net radiation.

Magnon-drag thermoelectric power

Abstract: The contribution of magnons to thermoelectric power may be appreciable in ferromagnets at sufficiently low temperatures. In this paper an analysis of the magnon-drag thermoelectric power has been given and a qualitative estimate of magnon contribution to the thermoelectric power and the effect of magnetic field has been obtained.