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Bismuth telluride (Bi₂Te₃) is a grey powder that is a compound of bismuth and tellurium also known as Bismuth(III) telluride. It is a semiconductor which is an efficient thermoelectric material for refrigeration or portable power generation.

Thermoelectric properties

Bismuth Telluride is a narrow gap layered semiconductor with a trigonal unit cell and point group symmetry of R3barm. The valence and conduction band structure can be described as a many ellipsoidal model with 6 constant energy ellipsoids that are centered on the reflection planes.² Bi₂Te₃ cleaves easily along the trigonal axis due to Van der Waals bonding between neighboring tellurium atoms. Due to this, Bismuth Telluride based material that is used for power generation or cooling applications must be polycrystalline. Furthermore, The Seebeck Coefficient of bulk Bi₂Te₃ becomes compensated around room temperature, forcing the materials used in power generation devices to be an alloy of Bismuth, Antimony, Tellurium, and Selenium.³

Recently, researchers have attempted to improve the efficiency of Bi₂Te₃ based materials by creating structures where one or more dimension is reduced, such as nanowires or thin films. In one such instance N-type bismuth telluride was shown to have an improved Seebeck coefficient (voltage per unit temperature difference) of -287 μV/K at 54 Celsius, ⁴ Its thermoelectric utility is also assisted by the combination of its high electrical conductivity of 1.1 × 10⁵ Siemens per meter with its very low latticethermal conductivity of 1.20W/(m*K), similar to ordinary glass.⁵

Occurrence

The mineral form of Bi₂Te₃ is tellurobismuthite which is moderately rare. There are many natural bismuth tellurides of different stoichiometry, as well as compounds of the Bi-Te-S-(Se) system, like Bi₂Te₂S (tetradymite).

See also

• Thermoelectricity
• Thermoelectric effect

References

1. ^ [Electrical and Thermal Properties of Bi2Te3. Phys. Rev. vol 108. no 5 1957 ]
2. ^ [Anisotropy of the constant energy surfaces in p-type Bi2Te3 and Bi2Se3from galvanomagnetic coefficients. Phys. Rev. B. vol 2. no 8. 1970]
3. ^ [Electrical and Thermal Properties of Bi₂Te₃. Phys. Rev. vol 108. no 5 1957 ]
4. ^ Thermoelectric properties of bismuth telluride thin films deposited by radio frequency magnetron sputtering
5. ^ Thermal conductivity measurements of Bismuth Telluride thin films by using the 3 Omega method

• The performance of bismuth telluride thermojunctions, H. J. Goldsmid, A. R. Sheard and D. A. Wright, Br. J. Appl. Phys. vol. 9 pp. 365-370 (1958) doi:10.1088/0508-3443/9/9/306

External links

• Thermoelectricity diagrams
• How kerosene refrigerator works
• Image:Kerosene_radio.jpg
• History of thermoelectric devices
• International Thermoelectric Society
• Thermoelectric News
• Tellurex thermoelectric module
• Amerigon
• MSDS at espimetals.com

Wikipedia content modification information:

• This page was last modified on 17 November 2008, at 11:39.

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