On the Challenges of Reducing Contact Resistances in Thermoelectric Generators Based on Half-Heusler Alloys

A method using fast hot pressing to join half-Heusler (HH) thermoelectric materials directly to an electrical current collector (Ag electrode) without using a third filler material is introduced. The compositions of the HH alloys used are Hf0.5Zr0.5CoSn0.2Sb0.8 and Ti0.6Hf0.4NiSn for p- and n-type, respectively. Using this method, the quality of the HH–electrode contacts is improved due to their low electrical contact resistance and less reaction–diffusion layer. The microstructure and chemical composition of the joints were examined using a scanning electron microscope equipped with energy-dispersive x-ray analysis. The electrical characteristics of the interfaces at the contacts were studied based on electrical contact resistance and Seebeck scanning microprobe measurements. In this paper, we show that joining the HH to a Ag electrode directly using fast hot pressing resulted in lower contact resistance and better performance compared with the method of using active brazing filler alloy.

[1]  Krzysztof Tomasz Wojciechowski,et al.  High temperature CoSb3-Cu junctions , 2011, Microelectron. Reliab..

[2]  D. Rowe.  CRC Handbook of Thermoelectrics , 1995 .

[3]  M. Mikami,et al.  Power Generation Performance of Thermoelectric Module Consisting of Sb-Doped Heusler Fe2VAl Sintered Alloy , 2011 .

[4]  C. Liao,et al.  Effect of Interfacial Compound Formation on Contact Resistivity of Soldered Junctions Between Bismuth Telluride-Based Thermoelements and Copper , 2007 .

[5]  Hui Wang,et al.  Stronger phonon scattering by larger differences in atomic mass and size in p-type half-Heuslers Hf1−xTixCoSb0.8Sn0.2 , 2012 .

[6]  N. Pryds,et al.  Segmentation of low‐cost high efficiency oxide‐based thermoelectric materials , 2015 .

[7]  K. Kubo,et al.  Development of a Thermoelectric Module Using the Heusler Alloy Fe2VAl , 2009 .

[8]  Gang Chen,et al.  Enhanced thermoelectric figure of merit of p-type half-Heuslers. , 2011, Nano letters.

[9]  Yongfu Zhu,et al.  Brief review of oxidation kinetics of copper at 350 °C to 1050 °C , 2006 .

[10]  Xiangyang Huang,et al.  Enhanced thermoelectric performance by the combination of alloying and doping in TiCoSb-based half-Heusler compounds , 2009 .

[11]  I. Karakaya,et al.  The Ag-Zr (silver-zirconium) system , 1992 .

[12]  C. Goupil,et al.  Design of Apparatus for Ni/Mg2Si and Ni/MnSi1.75 Contact Resistance Determination for Thermoelectric Legs , 2014, Journal of Electronic Materials.

[13]  Yongfu Zhu,et al.  Oxidation Mechanism of Copper at 623-1073 K , 2002 .

[14]  B. Balke,et al.  Phase separation as a key to a thermoelectric high efficiency. , 2013, Physical chemistry chemical physics : PCCP.

[15]  Claudia Felser,et al.  Enhanced thermoelectric performance in the p-type half-Heusler (Ti/Zr/Hf)CoSb0.8Sn0.2 system via phase separation. , 2014, Physical chemistry chemical physics : PCCP.

[16]  G. J. Snyder,et al.  Bonding and interfacial reaction between Ni foil and n-type PbTe thermoelectric materials for thermoelectric module applications , 2014, Journal of Materials Science.

[17]  S. Sakurada,et al.  Effect of Ti substitution on the thermoelectric properties of (Zr,Hf)NiSn half-Heusler compounds , 2005 .

[18]  N. Pryds,et al.  Optimization of the Mechanical and Electrical Performance of a Thermoelectric Module , 2015, Journal of Electronic Materials.

[19]  Basel I. Ismail,et al.  Thermoelectric Power Generation Using Waste-Heat Energy as an Alternative Green Technology , 2009 .

[20]  Di Wu,et al.  Half-Heusler phases and nanocomposites as emerging high-ZT thermoelectric materials , 2011 .

[21]  Lidong Chen,et al.  Fabrication of a CoSb3-based thermoelectric module , 2010 .

[22]  J. Sharp,et al.  Practical Contact Resistance Measurement Method for Bulk Bi2Te3-Based Thermoelectric Devices , 2014, Journal of Electronic Materials.

[23]  F. C. Nix,et al.  The Thermal Expansion of Pure Metals. II: Molybdenum, Palladium, Silver, Tantalum, Tungsten, Platinum, and Lead , 1942 .

[24]  G. J. Snyder,et al.  Beneficial Contribution of Alloy Disorder to Electron and Phonon Transport in Half‐Heusler Thermoelectric Materials , 2013 .

[25]  N. Pryds,et al.  Characterization of the interface between an Fe–Cr alloy and the p-type thermoelectric oxide Ca3Co4O9 , 2014 .

[26]  A. Weidenkaff,et al.  Half-Heusler (TiZrHf)NiSn Unileg Module with High Powder Density , 2013, Materials.

[27]  G. J. Snyder,et al.  Towards high efficiency segmented thermoelectric unicouples , 2014 .

[28]  Gang Chen,et al.  Enhancement in Thermoelectric Figure‐Of‐Merit of an N‐Type Half‐Heusler Compound by the Nanocomposite Approach , 2011 .

[29]  M. Mikami,et al.  Development and Evaluation of High-Strength Fe2VAl Thermoelectric Module , 2008 .

[30]  G. J. Snyder,et al.  Segmented Thermoelectric Oxide‐Based Module for High‐Temperature Waste Heat Harvesting , 2015 .

[31]  A. Michaelis,et al.  Development of laser-based joining technology for the fabrication of ceramic thermoelectric modules , 2014 .

[32]  Soon-Mok Choi,et al.  A Resistance Ratio Analysis for CoSb3-Based Thermoelectric Unicouples , 2012, Journal of Electronic Materials.

[33]  K. Bartholomé,et al.  Thermoelectric Modules Based on Half-Heusler Materials Produced in Large Quantities , 2014, Journal of Electronic Materials.

[34]  H. Okamoto.  Cu-Ti (Copper-Titanium) , 2002 .

[35]  J. Dugué,et al.  Experimental study of the ternary Ag―Cu―In phase diagram , 2009 .