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 α-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 MgAg_0.97Sb 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 (μ ∼130 cm² V⁻¹ s⁻¹), minimized secondary-phase content, and suppressed thermal conductivity (κ). Further analyses using weighted mobility (μ_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 α-MgAgSb as a highly promising candidate for sustainable, efficient, and practical low-temperature TE module applications.