PhD student at University of Tsukuba, majoring Materials Innovation, affiliated to the National Institute for Materials Science (NIMS) as a NIMS Junior Researcher, Thermal Energy Materials Group, Research Center for Materials Nanoarchitectonics (MANA).

Thermoelectric generators offer a promising solution for sustainable off-grid energy supply by harvesting waste heat. However, achieving high power density in thermoelectric generators is also highly desirable in confined areas, yet remains challenging. Here, we develop an eco-friendly magnesium-based thermoelectric generator with exceptional power output performance through synergistic material and device-level engineering. By selecting p-type MgAgSb, one of the most promising p-type materials to replace Bi2Te3 for power generation, we enhance its power factor while maintaining high zT. Through Cu doping and high-temperature annealing, optimized carrier concentration and improved carrier mobility are simultaneously achieved, resulting in a power factor and zT exceeding 24 µW cm-1 K-2 and 1.2, respectively. Based on this high-performance p-type MgAgSb, we further couple it with n-type Mg2Sn-based material, which intrinsically exhibits a higher power factor, exceeding 30 µW cm-1 K-2, than the conventional n-type Mg3Sb2, to fabricate a fully magnesium-based thermoelectric two-pair module. By leveraging the semiconductor-to-metal transition in MgAgSb, together with an increased temperature gradient across the device, the internal resistance is significantly reduced and the output voltage is increased, thereby substantially boosting power output performance. As a result, the device delivers a maximum power output of 0.4 W and a conversion efficiency of 6%, while also exhibiting high stability with no noticeable degradation after extended high-temperature operation. This work presents a promising fully magnesium-based thermoelectric generator beyond conventional MgAgSb-Mg2Sn-based couples. Despite moderate conversion efficiency, the remarkably high-power output performance highlights its strong potential to meet diverse power demands.

1. Wang, L.; Babu, J.; Mori, T. Nat. Sustain. 9 (7), 947–949 (2026) ttps://doi.org/10.1038/s41893-026-01826-7
2. Liu, Z.; Guo, Z.; Li, A.; Wang, L.; Sui, J.; Mori, T. Nat. Rev. Mater, 2058-8437 (2026) https://doi.org/10.1038/s41578-026-00923-5