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Silicon-germanium (SiGe) thermoelectrics have been used for converting heat into power in spacecrafts designed for deep-space NASA missions since 1976. This material is used in the radioisotope thermoelectric generators (RTGs) that power ''Voyager 1'', ''Voyager 2'', ''Galileo'', ''Ulysses'', ''Cassini'', and ''New Horizons'' spacecrafts. SiGe thermoelectric material converts enough radiated heat into electrical power to fully meet the power demands of each spacecraft. The properties of the material and the remaining components of the RTG contribute towards the efficiency of this thermoelectric conversion. == Properties == Heavily doped semiconductors, such as silicon-germanium (SiGe) thermoelectric couples (also called thermocouples or unicouples), are used in space exploration. SiGe alloys consist of thermoelectric properties. Their performance in thermoelectric power production is characterized by high dimensionless figures-of-merit (ZT) under high temperatures, which has been shown to be near 2 in some nanostructured-SiGe models. SiGe alloy devices are mechanically rugged and can withstand severe shock and vibration due to its high tensile strength (i.e. >7000 psi) and low dislocation density.〔〔(【引用サイトリンク】first1=Jeremy G. )〕 SiGe material is malleable with standard metallurgical equipment and bonds easily to construct components.〔 SiGe alloy devices can operate under high temperatures (i.e. >1300 ˚C) without degradation due to their electronic stability, low thermal expansion coefficient and high oxidation resistance.〔〔 Near the sun, solar cell performance deteriorates from high incident particle flux and high temperatures from heat flux. However, thermoelectric energy conversion systems that use thermoelectric materials (e.g. SiGe alloys) as a supplemental source of power for missions near the sun can operate unprotected in vacuum and air environments under high temperatures due to their low sensitivity to radiation damage.〔 Such properties have made SiGe thermoelectrics convenient for power generation in space. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Application of silicon-germanium thermoelectrics in space exploration」の詳細全文を読む スポンサード リンク
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