Solid-state thermoelectric generators (TEGs) are promising solution for waste heat recovery. However, they typically suffer from lower conversion efficiency, lack of reliable high temperature device fabrication process and long-term stability. In order to realize high electrical conversion efficiency (ECE) in TEGs, it is critical that in conjunction with high TE materials figure of merit, zT, there is also a reliable TE module fabrication process. This study demonstrates the TEG fabrication process that results in reduced thermal and electrical contact resistances between metal electrodes and TE legs, even at high temperatures (>600 °C). The fabrication approach is demonstrated using p-type ZrCoSb-based and n-type ZrNiSn-based half-Heusler TE materials. High temperature brazing material is used as a filler that enables direct bonding of TE legs to the copper electrode without metallizing legs. This technique improves the TEG performance and stability at high temperatures by minimizing the contact resistance and diffusion at TE leg/electrode interface. The fabricated modules exhibit a high power density of ~11.5 Wcm−2 and an ECE of 9.5% at 670 °C temperature gradient. The module was exposed to longtime soaking at 550 °C in air and was found to exhibit negligible deterioration. These results are highly promising for advancing the TE modules in waste heat recovery applications.
|Original language||English (US)|
|Journal||Journal of Power Sources|
|State||Published - May 1 2021|
Bibliographical noteFunding Information:
U.S., B.P. and H.Z. acknowledge the financial support from the DARPA MATRIX program (NETS). A.N. acknowledges the financial support through NSF-CREST grant number HRD 1547771 . S.P. and H.B.K. acknowledge the financial support through the Office of Naval Research through award number N00014-20-1-2602 . W.L. acknowledges the support through Army RIF program. C.D. acknowledges the support through the National Science Foundation IUCRC: Center for Energy Harvesting Materials and Systems.
- Air stability
- Contact resistance
- Direct bonding
- Waste heat recovery