Effect of the Fabrication Technique on the Thermoelectric Performance of Mg-Based CompoundsA Case Study of n‑Type Mg₂Ge

High performance, low cost, and low toxicity have been the main characteristics associated with magnesium-based thermoelectric materials. Nevertheless, the high volatility of magnesium creates challenges in the synthesis of these materials. In this work, n-type Mg₂Ge is synthesized using a solid-state technique, fully characterized, and compared with Mg₂Ge fabricated through different processes. We have found that Bi is an ineffective dopant in Mg₂Ge and precipitates into Mg₂Bi₃. Regardless of the technique used, the loss of Mg by evaporation and formation of precipitates in Bi-doped samples resulted in a low charge carrier concentration and, consequently, a low power factor. The precipitates significantly reduced the lattice thermal conductivity, however, leading to a figure-of-merit, <i>zT</i>, of 0.4 at 725 K, improving the previously reported figure-of-merit, <i>zT</i>, of 0.2 for Sb-doped Mg₂Ge. This work highlights the impact of the fabrication technique on the thermoelectric performance of Mg-based compounds