Realizing 10% Conversion Efficiency by Contact Engineering of Mg3Sb1.5Bi0.5 for Medium Temperature Thermoelectric Power Generation

Parasitic losses at various interfaces play a crucial role in determining the thermoelectric (TE) generator performance. In this work, we adopt an approach wherein the interface contact resistance can be minimized by using a combination of the multilayer (ML) contacting technique and transient liquid phase (TLP) bonding. The technique was experimentally verified with doped Mg3Sb1.5Bi0.5. First, a contacted leg consisting of the TE material, the diffusion barrier layer, and an outer metallic (copper) layer was prepared by the ML process. This was then joined to a copper bridge (mimicked by copper holders) by using the TLP process with tin as the brazing element. Our contact resistance measurements indicate an extremely low value corresponding to 2.5% of the total resistance for the TLP-joined layer, which corresponds to a similar to 2.6% lowering of the peak efficiency (eta(max)) value compared to that of an uncontacted leg. Thermoelectric generator (TEG) measurements were obtained for the contacted leg. The contacted leg exhibited an eta(max) value of similar to 10% and a power output of 80 mW when it was subjected to a temperature gradient (Delta T) of 330 K. These results demonstrate that, by combining ML contacting with TLP bonding, interface contact engineering can be a potential method for enhancing TE performance.