Reproducible synthesis of α-MgAgSb with optimized carrier transport for low-temperature thermoelectric applications

Abstract

Developing reproducible, high-performance thermoelectric (TE) materials for cooling and low-grade heat recovery applications remains a pressing challenge, particularly for tellurium-free systems. In this study, we systematically optimize the synthesis of alpha-MgAgSb via two-step ball milling, spark plasma sintering (SPS), and targeted post-annealing. We demonstrate that sintering at 673 K, followed by a 3-days annealing period and an additional low-temperature stabilization step, yields MgAg0.97Sb samples with minimal secondary phases, high TE performance and excellent reproducibility. The optimized materials achieve a maximum zT of 0.84 near room temperature and reach 1.3 at 500 K, placing them among the highest-performing Te-free p-type TE materials reported to date. These significant enhancements are attributed to improved Hall mobility (mu similar to 130 cm2 V-1 s-1), minimized secondary-phase content, and suppressed thermal conductivity (kappa). Further analyses using weighted mobility (mu w) and the TE quality factor (B) confirm that the carrier concentration (n) closely approaches the theoretical optimum, providing strong alignment between experimental and predicted zT values. This research establishes a robust and scalable synthesis protocol, highlighting alpha-MgAgSb as a highly promising candidate for sustainable, efficient, and practical low-temperature TE module applications.