Abstract Thermoelectric materials are attractive for sustainable energy applications due to their ability to convert waste heat into electricity. However, one of the main hindrances to their widespread adoption is the stringent requirements during their synthesis and processing, and therefore affects their overall cost and sustainability. For instance, Mg-containing compounds generally requires processing in high vacuum or Argon protected atmosphere, which are less readily available. In this work, we demonstrate higher thermoelectric performance by synthesizing Mg2Si-based compounds in N2 compared to Ar atmosphere. The high performance originated from simultaneous improvement in electrical conductivity and reduced thermal conductivity. In addition, the introduction of Sn-alloying as well as Zn- and Bi- co-doping further improved both electronic and thermal transport properties, resulting in peak zT near 1.0 at 760 K for Mg1.9925Zn0.0075Si0.48Sn0.5Bi0.02. Owing to the much lower cost of N2 compared to Ar owing to their much higher relative abundance, such processing strategy is expected to reduce cost and improve sustainability. Furthermore, the insights derived from this work can potentially be applied to other compounds containing Mg- and other reactive elements. Fundamentally, this result will also motivate further studies on the intrinsic defect formation in N2 vs Ar atmosphere, which affects both electronic and thermal transports.
