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Electrical Contact Fabrication and Measurements of Metals and Alloys to Thermoelectric Materials

Published online by Cambridge University Press:  01 February 2011

Jonathan James D'Angelo
Affiliation:
dangelo4@msu.edu, Michigan State University, Electrical and Computer Engineering, 2120 Engineering Building, East Lansing, MI, 48823, United States, 517-432-1965
Edward J Timm
Affiliation:
timm@egr.msu.edu, Michigan State University, Mechanical Engineering, East Lansing, MI, 48823, United States
Fei Ren
Affiliation:
renfei@egr.msu.edu, Michigan State University, Chemical Engineering and Material Science, East Lansing, MI, 48823, United States
Bradley D Hall
Affiliation:
hallbra6@msu.edu, Michigan State University, Chemical Engineering and Material Science, East Lansing, MI, 48823, United States
Eldon Case
Affiliation:
casee@egr.msu.edu, Michigan State University, Chemical Engineering and Material Science, East Lansing, MI, 48823, United States
Harold Schock
Affiliation:
schock@msu.edu, Michigan State University, Mechanical Engineering, East Lansing, MI, 48823, United States
Mercouri Kanatzidis
Affiliation:
m_kanatzidis@northwestern.edu, Northwestern University, Chemistry, Evanston, IL, 60208, United States
Duck Young Chung
Affiliation:
dychung@anl.gov, Argonne Nation Laboratory, Material Science Division, Argonne, IL, 60439, United States
Timothy P Hogan
Affiliation:
hogant@msu.edu, Michigan State University, Electrical and Computer Engineering, East Lansing, MI, 48823, United States
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Abstract

Low electrical contact resistance is essential for the fabrication of high efficiency thermoelectric generators in order to convert heat to electricity. These contacts must be stable to high temperatures and through thermal cycling. A ratio of the contact resistance to the leg resistance below 0.1 is the goal for fabrication of a high efficiency thermoelectric power generation device. Here we present the fabrication procedures and characterization of contacts of metal alloys to Pb-Sb-Ag-Te (LAST) and Pb-Sb-Ag-Sn-Te (LASTT) compounds. Contacts were fabricated and measured for both ingot and hot pressed materials. Stainless steel 316 has shown a low resistance contact to these thermoelectric materials when the proper bonding conditions are used. Different time-temperature-pressure conditions for bonding to n-type and to p-type legs are presented. Contact resistances below 10μΩcm2 have been measured. In addition, break tests have shown bond strengths exceeding the semiconductor fracture strength. One of the considerations used in selecting iron alloys for electrical interconnects is the similarity in the coefficient of thermal expansion to the LAST and LASTT materials which is 18 ppm/°C and relatively temperature insensitive. Contacts to the thermoelectric materials were accomplished by diffusion bonding in a furnace developed in our lab at Michigan State University. The furnace is capable of reaching temperatures of up to 1000°C with a controlled atmosphere of a reducing gas. Fabrication procedures and contact data are presented in this paper.

Type
Research Article
Copyright
Copyright © Materials Research Society 2008

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