Novel fast synthesis route for α-MgAgSb thermoelectric materials

Abstract

Thermoelectric (TE) materials capable of waste heat recovery in the temperature range of 300–525 K remain relatively underdeveloped compared to conventional Bi₂Te₃-based systems, which present inherent environmental, health, and cost challenges. Recently, MgAgSb-based compounds have garnered significant research interest for applications in this temperature range owing to their intrinsically low thermal conductivity, high figure of merit and higher abundance. However, synthesis of the desired low-temperature α-MgAgSb phase typically requires highly controlled production processes—such as multi-step mechanical alloying, followed by extensive, week-long annealing—to mitigate the formation of or transition to undesirable phases. This study proposes an original, rapid, and scalable synthesis strategy combining induction melting for only six minutes with the subsequent classic hot-pressing method. We investigated the effect of nominal stoichiometry on thermoelectric performance by synthesising three distinct compositions: MgAg_0.97Sb_0.995, MgAg_0.965Sb_0.985, and MgAg_0.955Sb_0.985. The MgAg_0.955Sb_0.985 composition exhibited optimal performance, achieving an average power factor (PF) of 12.8 μW K⁻² cm⁻¹ in the 300–525 K range. By considerably reducing the thermal budget and processing time, this approach significantly improves the energy payback time (EPBT) and reduces the carbon footprint of production, addressing the critical sustainability-performance trade-off that limits large-scale deployment. This result validates the capacity of the proposed fast synthesis route to yield performant MgAgSb-based samples and suggests that the optimal nominal composition is dependent on the specific production technique employed. Fundamentally, this work demonstrates the rapid and successful preparation of the desired α-MgAgSb phase using an easily scalable technique that does not require a perpetually inert atmosphere. This process utilises bulky precursor elements directly, significantly reducing production complexity, associated costs, and health hazards. This advancement provides a simpler and more industrially viable pathway for the transition of MgAgSb materials toward commercial availability.