Improving Thermoelectric Conversion Efficiency of Mg₃(Sb, Bi)₂-Based TE Materials via Interface Contact Layer Optimization

Mg3(Sb, Bi)2-based compounds have recently attracted intense attention as thermoelectric (TE) materials for power generation and cooling applications because of their high TE performance. The contact interface layers play a crucial role in achieving a high conversion efficiency of TE devices. Iron contacts have often been used for the Mg3(Sb, Bi)2 compound; however, a large drawback for device fabrication is their incompatibility with solder. In this study, we developed cupronickel as a potential interface contact layer for Mg3(Sb, Bi)2. A crack-free interface with a low specific contact resistance of ∼5 μΩ cm2 enables a maximum conversion efficiency (ηmax) of ∼8% for the single-leg cupronickel/Mg3(Sb, Bi)2/cupronickel. Additionally, a ηmax of ∼7.8% is realized for a 2-pair module of Mg3(Sb, Bi)2 and MgAgSb at a temperature difference (ΔT) of 277 K. The optimization of the cupronickel contact layer in this study has the potential to enhance the conversion efficiency of Mg3(Sb, Bi)2-based compounds.