Advances in Magnesium-Based Thermoelectrics: A Critical Review

In recent years, magnesium-based thermoelectric materials have emerged as a key research direction toward large-scale applications, owing to their elemental abundance, low material cost, good environmental compatibility, and competitive thermoelectric performance in the low-to-mid temperature range. Given the rapid progress achieved in this field, this review systematically surveys the latest advances in three representative classes of magnesium-based thermoelectric materials: Mg₃X₂ (X = Sb, Bi), MgAgSb, and Mg₂X (X = Si, Ge, Sn). Emphasis is placed on their crystal structures and electronic band features, phonon transport behavior, and carrier scattering mechanisms, together with a discussion of bulk and thin-film fabrication strategies and their impacts on thermoelectric performance. Commonalities and distinct characteristics of performance optimization through carrier concentration tuning, band engineering, microstructural design, and interface engineering are summarized. Furthermore, key challenges associated with chemical and thermal stability as well as device integration are critically assessed, and device-level design principles such as electrode contacting, diffusion barrier layers, and substrate selection are systematically reviewed. Finally, considering the current physical and engineering bottlenecks, several critical directions for the future development of magnesium-based thermoelectric materials are proposed, highlighting the importance of a paradigm shift from "material-level performance optimization" toward "material-device-system co-design" to accelerate their practical deployment.