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Thermoelectric Effects - Early study of Thermoelectricity

In the years before the world wars thermoelectricity was discovered and developed in western Europe by academic scientists, with much of the activity centered in Berlin.

Seebeck Effect

In Thomas Johann Seebeck found that a circuit made from two dissimilar metals, with junctions at different temperatures would deflect a compass magnet [1].

Seebeck initially believed this was due to magnetism induced by the temperature difference and thought it might be related to the Earth's magnetic field. However, it was quickly realized that a "Thermoelectric Force" induced an electrical current, which by Ampree's law deflects the magnet.

Seebeck biography Thermoelements also have a much smaller heat capacity than conventional thermometers e. Then, copy and paste the text into your bibliography or works cited list. Complete Dictionary of Scientific Biography. Learn more about citation styles Citation styles Encyclopedia.

More specifically, the temperature difference produces and electric potential (voltage) which can drive an electric current in a closed circuit. Today, this is known as the Seebeck effect.

Thomas Seebeck

Instrument used by Seebeck to observe the deflection of a compass needle (a) due to a thermoelectric induced current from heating the junction of two different metals (n and o).

 

The voltage produced is proportional to the temperature difference between the two junctions. The proportionality constant (S or a) is known as the Seebeck coefficient, and often referred to as "thermopower" even though it is more related to potential than power.

In Gustav Magnus discovered the Seebeck voltage does not depend on the distribution of temperature along the metals between the junctions [2] an indication that the thermopower is a thermodynamic state function. This is the physical basis for a thermocouple, which is used often for temperature measurement.

Gustav Magnus

V = a(Th - Tc) The voltage difference, V, produced across the terminals of an open circuit made from a pair of dissimilar metals, A and B, whose two junctions are held at different temperatures, is directly proportional to the difference between the hot and cold junction temperatures, Th - Tc [2].

 

Seebeck surveyed many different materials: elements, alloys and minerals including zinc antimonide, chalcogenide minerals such as PbS and cobalt arsenide and made a qualitative ordering of their relative Seebeck effect.

Seebeck biography death These are color figures which originate inside glass volume after cooling. Victor Frederick Weisskopf. Seeberg, Reinhold. More From encyclopedia.

In Werner Haken, following the studies on ZnSb and CdSb of Becquerel [3], quantitatively characterized the Seebeck coefficient (now in uV/K) and electrical conductivity of many elements, alloys and compounds correctly identifying Sb2Te3, Bi2Te3, BiSb, SnTe, Cu-Ni alloys as good thermoelectric materials and even studied PbTe [4].

 

Peltier Effect In , a French watchmaker and part time physicist, Jean Charles Athanase Peltier found that an electrical current would produce heating or cooling at the junction of two dissimilar metals. In Lenz showed that depending on the direction of current flow, heat could be either removed from a junction to freeze water into ice, or by reversing the current, heat can be generated to melt ice. The heat absorbed or created at the junction is proportional to the electrical current. The proportionality constant is known as the Peltier coefficient.

Jean Charles A. Peltier

Thomson Effect Twenty years later, William Thomson (later Lord Kelvin) [5] issued a comprehensive explanation of the Seebeck and Peltier Effects and described their interrelationship (known as the Kelvin Relations). The Seebeck and Peltier coefficients are related through thermodynamics. The Peltier coefficient is simply the Seebeck coefficient times absolute temperature. This thermodynamic derivation led Thomson to predict a third thermoelectric effect, now known as the Thomson effect. In the Thomson effect, heat is absorbed or produced when current flows in a material with a temperature gradient. The heat is proportional to both the electric current and the temperature gradient. The proportionality constant, known as the Thomson coefficient is related by thermodynamics to the Seebeck coefficient.

William Thomson (Lord Kelvin)

 

Edmund Altenkirch was the first to use the constant property model to derive the maximum efficiency of a thermoelectric generator () as well as the performance of a cooler () when the design and operating conditions are fully optimized [6].

Seebeck meaning

Seebeck peltier and thomson effect

Relation between seebeck coefficient and peltier coefficient

Seebeck effect

This correct relationship, later developed into the 'figure of merit' zT, that good thermoelectric materials should possess large Seebeck coefficients, high electrical conductivity (to minimize Joule heating due to electrical resistance) and low thermal conductivity (to minimize heat loss). Early thermal conductivity measurements by A Eucken [7] on solids quickly revealed that point defects found in alloys significantly reduces lattice thermal conductivity - a strategy that becomes important for thermoelectric materials.

 

Thermoelectric Applications - Excitement and Disappointment -

During and after the world wars thermoelectricity was actively studied for use in valuable technologies, primarily cooling as well as power generation for military as well as civilian uses.

The political and economic importance of such devices made advances more difficult and slow to publicise particularly between the Eastern European and Western countries. By the 's, generator efficiencies had reached 5% and cooling from ambient to below 0 C was demonstrated which has ultimately lead to some viable industries.

Many thought thermoelectrics would soon replace conventional heat engines and refrigeration and interest and research in thermoelectricity grew rapidly at major appliance corporations such as Westinghouse, universities and national research laboratories [8]. However, by the end of the 's the pace of progress had slowed with some discussion that the upper limit of zT might be near 1 and many research programs were dismantled (despite several reports of zT > 1).

 

Abram F. Ioffe

Oil burning lamp powering a radio using the first commercial thermoelectric generator containing ZnSb and constantan built in USSR beginning in [9]

 

Figure of Merit zT
In Abram Fedorovich Ioffe developed the modern theory of thermoelectricity using the concept of the 'figure of merit' zT, culminating in the classic texts on Semiconductor Thermoelements and Thermoelectric Cooling () [9].

Ioffe also promoted the use of the semiconductors in thermoelectrics and semiconductor physics to analyze results and optimize performance. Materials with high thermoelectric figures of merit are typically heavily doped semiconductors, the best known are the tellurides of antimony, bismuth and lead. Ioffe and his institute in Saint Petersburg actively pursued thermoelectric research and development in USSR leading to some of the first commercial thermoelectric power generation and cooling devices.

Ioffe was one of the first to promote the use of alloying to reduce lattice thermal conductivity by point defects.

 

One of the first demonstrations of 0 C cooling was by H. Julian Goldsmid in using thermoelements based on Bi2Te3 [10]. Seebeck biography book Cite this article Pick a style below, and copy the text for your bibliography. A thermocouple consists of two wires of different metals that are joined to form a closed loop. See, Carolyn. Then, copy and paste the text into your bibliography or works cited list. Goldsmid was one of the first to utilize the thermoelectric quality factor, identifying the importance of high mobility and effective mass combination and low lattice thermal conductivity in semiconductors that when properly doped make good thermoelectric materials. Goldsmid authored many introductory books including Introduction to Thermoelecricity ().

H. Julian Goldsmid

 

In the search for high zT materials, a general strategy guided by the quality factor has been to look for small band gap semiconductors made from heavy elements. Glen Slack summarized the material requirements succintly in the "phonon-glass electron-crystal" concept that the phonons should be disrupted like in a glass but the electrons should have high mobility like they do in crystalline semiconductors [11].

 

Thermoelectric Industry - Niche Applications -

The reliability and simplicity of thermoelectricity enables niche applications for this solid-state technology even while conventional processes are more efficient.

Besides thermocouples, a small but stable industry to produce Peltier coolers based on Bi2Te3-Sb2Te3 formed which now produce coolers for a variety of products ranging from optoelectronics, small refrigerators and seat cooling/heating systems. The need for reliable, remote power sources provids some niche applications for thermoelectric power generation.

The maturity of the science, technology and commercial use of thermoelectricity has lead to a number of focused scientific meetings and organizations, the largest of which is the International Thermoelectric Society with meetings since

 

USA missions utilizing Radioisotope Thermoelectric Generators for Electrical Power

 

Thermoelectric Generators for Space For Space Exploration missions, particularly beyond the planet Mars, the light from the sun is too weak to power a spacecraft with solar panels. Seebeck biography wikipedia Seebeck experimentally verified Brewster's law, which relates the refractive index of a material to the angle of complete polarization. Thomas J. Science Dictionaries thesauruses pictures and press releases Seebeck, Thomas. Thomas Henry Huxley. Instead, the electrical power is provided by converting the heat from a Pu heat source into electricity using thermoelectric couples. Such Radioisotope Thermoelectric Generators (RTG) have been used by NASA in a variety of missions such as Apollo, Pioneer, Viking, Voyager, Galileo and Cassini. With no moving parts, the power sources for Voyager are still operating, allowing the spacecraft to continue to make scientific discoveries after over 35 years of operation. The Curiosity rover on Mars is the first rover powered by thermoelectrics using a Multi-Mission RTG (MMRTG).

Radioisotope Thermoelectric Generator (RTG)Used on Voyager 1 & 2

 

New Concepts in Thermoelectricity

Interest in thermoelectricity renewed in the 's with the influx of new ideas.

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The hope that engineered structures will improve zT, particularly at the nanometer scale has reinvigorated research in thermoelectric materials [12]. While some of these ideas have shown to be ineffective, others have lead to entirely new classes of complex thermoelectric materials [13].

The global need for alternative sources of energy has revived interest in commercial applications [14] (see Energy Sustainability Page) and stimulated interest in developing inexpensive and environmentally-friendly thermoelectric materials.

REFERENCES

[1] Th. J. Seebeck "Magnetische Polarisation der Metalle und Erze Durch Temperatur-Differenz" in Ostwald's Klassiker der Exakten Wissenshaften Nr. 70 (). Seebeck Biography 1. Seebeck Biography 2.
[2] G. Magnus, Poggendorf's Annalen der Physik 83 p ()

[3] E.

Becquerel, Ann. de chim. et phys. (4) 8. ()

[4] W. Haken, Annalen der Physik p ()

[5] W. Thomson "On the Dynamical Theory of Heat. Trans." R. Soc. Edinburgh: Earth Sci. 3,
91–98 (). Thomson Biography.
[6] E. Altenkirch, Physikalische Zeitschrift 10, – (); Physikalische Zeitschrift 12, ()

[7] A. Eucken and G.

Kuhn Z. Phys. Chem. p ()

[8] R. R. Heikes and R. W. Ur, "Thermoelectricity: Science and Engineering" Interscience
Publishers, (); I. B. Cadoff and E. Miller "Thermoelectric Materials and Devices"
Materials Technology Series. Reinhold Publishing Cooperation (); P. H. Egli "Thermoelectricity" John Wiley & Sons ()

[9] M.

V. Vedernikov and E. K. Iordanishvili "A. F. Ioffe and origin of modern semiconductor thermoelectric energy conversion" 17th Int. Conf.

Seebeck biography pdf: Half of the junctions of the thermopile are shielded within the detector, whereas the other half are exposed to external heat radiation which is recorded through a voltmeter in the thermopile circuit. Thomas Moran. Lipton Company. Thomas Kennerly Wolfe Jr.

on Thermoelectrics vol 1, pp 37–42 (); A. F. Ioffe "Semiconductor Thermoelements and Thermoelectric Cooling"

[10] H. J. Goldsmid and R. W. Douglas "The use of semiconductors in thermoelectric refrigeration" British J. Appl. Phys. 5, ()

[11] Glen Slack in CRC Handbook of Thermoelectrics (ed. Rowe, M.) p– ().
[12] M.S.

Dresselhaus, et al. "New directions for low-dimensional thermoelectric
materials" Adv. Mater. 19, – (); M. G. Kanatzidis "Nanostructured thermoelectrics: the new paradigm?" Chem. Mater. 22, – ()

[13] G. J. Snyder and E. Toberer "Complex Thermoelectric Materials" Nature Materials 7, ()

[14] L.

Bell "Cooling, Heating, Generating Power, and Recovering Waste Heat with Thermoelectric Systems" Science Vol. pp. ()