Intermetallic Growth at the Interfaces Between Zn4Sb3 Thermoelectric Material and Various Metallic Electrodes

Abstract

Zn 4 Sb 3 has received interest for thermoelectric (TE) applications due to its low cost and low environmental impact. In this study, the Zn 4 Sb 3 TE material was diffusion-bonded with multiple electrode materials of Ni, Ag, Cu, Pd and Ti for evaluation of the manufacturing of TE modules. Intermetallic compounds formed at the interfaces of the Zn 4 Sb 3 diffusion couples, with Ni, Ag, Cu, and Pd exhibiting the selective reaction effect with zinc due to its high chemical affinity and low formation energies. Optimized bonding strengths of 6.6 to 8.2 MPa were achieved in Zn 4 Sb 3 bonded with Ni, Ag and Cu materials at 350 °C. The Pd material could only bond at a temperature above 300 °C, and cracks presented after longer bonding times. As for the titanium, Zn 4 Sb 3 /Ti was successfully joined only at temperatures between 400 °C and 500 °C. It was observed that a rather thin TiSb 2 intermetallic compound formed during the interfacial reactions between Zn 4 Sb 3 and Ti, which grew significantly more slowly than those formed at the interfaces of Zn 4 Sb 3 diffusion-coupled with Ni, Ag, Cu, and Pd metallic materials. Our results provide a reference for evaluating these common materials as suitable electrode and barrier layer candidates for utilizing the Zn 4 Sb 3 TE material.