Safdar Abbas Malik’s research while affiliated with Technical University of Denmark and other places

ZnSb is one of the promising low-cost p-type thermoelectric materials for constructing waste heat recovery devices operating in the medium temperature region (250 – 400 °C). To obtain high performance, these devices require stable and low resistance contacts between thermoelectric materials and metallic electrodes. In this paper, we investigate the joining of ZnSb to Ni and Ag electrodes using a commercial solder alloy S-Bond 400 and hot-pressing technique. Ti and Cr layers are also introduced as a diffusion barrier and microstructure at the interfaces is observed by scanning electron microscopy. We found that S-bond 400 solder reacts with Ag and Ni electrodes to form different alloys at the interfaces. Cr layer was found to be broken after joining, resulting in a thicker reaction/diffusion layer at the interface, while Ti layer was preserved.

The data presented in this article are related to the research article entitled: “Solder free joining as a highly effective method for making contact between thermoelectric materials and metallic electrodes” (Malik et al., 2017) [1]. This article presents microstructure obtained by scanning electron microscopy (SEM) and chemical analysis by energy dispersive X-ray spectroscopy (EDX) point measurements of the thermoelectric ZnSb legs after joining to metallic electrodes using solder (Zn-2Al) and free-soldering methods.

Quality of joining and interfacial evolution behavior play a critical role in the performance and reliability of thermoelectric (TE) devices. In this study, different joining methods using solder alloy (1) and solder-free joining with microlayers of Ti and Cr as interconnecting agents (2) were systematically investigated and demonstrated on the low-cost ZnSb TE system. ZnSb material, which was chosen to bond with Ag and Ni metallic electrodes, exhibited a maximum zT value of 0.8 at . With the joining method (1), Zn from the solder was found to diffuse/react with both Ag and Ni electrodes, and penetrate into ZnSb legs. SEM-EDX analysis recorded a significant excess of Zn in the ZnSb leg after joining. We found that, using microlayers of Ti and Cr as interconnecting agent, a very good interfacial contact was obtained, and the starting composition of ZnSb legs was preserved. The interfacial contact of was found to be stable after heat treatment at for 30 h, suggesting solder-free joining as an effective method for reliable contacts in TE devices in the medium temperature region ( ).