Reliable metal alloy contact for Mg3+δBi1.5Sb0.5 thermoelectric devices

Proper contacts between thermoelectric (TE) materials and electrodes are critical for TE power generation or refrigeration. The Bi-rich n-type Zintl material Mg3+δBi2-xSbx exhibits very good performance near room temperature, which makes Mg3+δBi2-xSbx-based compounds highly promising candidates to replace the Bi2Te3-ySey alloys, but ideal that can match their have not yet been well studied. Here we investigate different metal (Ni Fe) alloy (NiFe, NiCr, NiCrFe, stainless steel) on Mg3+δBi1.5Sb0.5. It is first shown low Schottky barrier narrow depletion region resulting from band degeneracy high carrier concentration of a heavily doped beneficial formation low-resistivity ohmic contact with alloy. Most fully optimized take advantage this. Second, it found NiFe/Mg3+δBi1.5Sb0.5 excellent thermal stability lowest resistivity among those studied after aging over 2100 h, attributed metallic NiMgBi NiFe Mg3+δBi1.5Sb0.5 layers. As buffer phase, effectively prevent elemental diffusion without negatively affecting electron transport. Benefiting such resistance, Mg3+δBi1.5Sb0.5/Bi0.4Sb1.6Te3 unicouple competitive conversion efficiency, 6% 150 K temperature difference hot-side 448 K.