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Thermal Expansion Studies of Selected High Temperature Thermoelectric MaterialsRadioisotope thermoelectric generators (RTGs) generate electrical power by converting the heat released from the nuclear decay of radioactive isotopes (typically plutonium-238) into electricity using a thermoelectric converter. RTGs have been successfully used to power a number of space missions and have demonstrated their reliability over an extended period of time (tens of years) and are compact, rugged, radiation resistant, scalable, and produce no noise, vibration or torque during operation. System conversion efficiency for state-of-practice RTGs is about 6% and specific power less than or equal to 5.1 W/kg. Higher specific power would result in more on-board power for the same RTG mass, or less RTG mass for the same on-board power. The Jet Propulsion Laboratory has been leading, under the advanced thermoelectric converter (ATEC) project, the development of new high-temperature thermoelectric materials and components for integration into advanced, more efficient RTGs. Thermoelectric materials investigated to date include skutterudites, the Yb14MnSb11 compound, and SiGe alloys. The development of long-lived thermoelectric couples based on some of these materials has been initiated and is assisted by a thermo-mechanical stress analysis to ensure that all stresses under both fabrication and operation conditions will be within yield limits for those materials. Several physical parameters are needed as input to this analysis. Among those parameters, the coefficient of thermal expansion (CTE) is critically important. Thermal expansion coefficient measurements of several thermoelectric materials under consideration for ATEC are described in this paper. The stress response at the interfaces in material stacks subjected to changes in temperature is discussed, drawing on work from the literature and project-specific tools developed here. The degree of CTE mismatch and the associated effect on the formation of stress is highlighted.
Document ID
20150014700
Acquisition Source
Jet Propulsion Laboratory
Document Type
Conference Paper
External Source(s)
Authors
Ravi, Vilupanur
(Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA, United States)
Firdosy, Samad
(Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA, United States)
Caillat, Thierry
(Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA, United States)
Brandon, Erik
(Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA, United States)
Van Der Walde, Keith
(ATA Engineering, Inc. San Diego, CA, United States)
Maricic, Lina
(ATA Engineering, Inc. San Diego, CA, United States)
Sayir, Ali
(NASA Glenn Research Center Cleveland, OH, United States)
Date Acquired
August 3, 2015
Publication Date
August 3, 2008
Subject Category
Solid-State Physics
Meeting Information
Meeting: International Conference on Thermoelectrics
Location: Corvallis, OR
Country: United States
Start Date: August 3, 2008
End Date: August 7, 2008
Sponsors: Oregon State Univ.
Distribution Limits
Public
Copyright
Other
Keywords
silicon germanium
zintl

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