Multifunctional composite magnet realizing record-high transverse thermoelectric generation†

Abstract

Permanent magnets are used in various products and essential for human society. If omnipresent permanent magnets could directly convert heat into electricity, they would lead to innovative energy harvesting and thermal management technologies. However, achieving such “multifunctionality” has been difficult due to poor thermoelectric performance of conventional magnets. In this work, we develop a multifunctional composite magnet (MCM) that enables giant transverse thermoelectric conversion while possessing permanent magnet features. MCM comprising alternately and obliquely stacked SmCo₅/Bi_0.2Sb_1.8Te₃ multilayers exhibits an excellent transverse thermoelectric figure of merit z_xyT of 0.20 at room temperature owing to the optimized anisotropic structure and extremely low interfacial electrical and thermal resistivities between the SmCo₅ and Bi_0.2Sb_1.8Te₃ layers. The MCM-based thermopile module generates a maximum of 204 mW at a temperature difference of 152 K, whose power density normalized by the heat transfer area and temperature gradient is not only record-high among transverse thermoelectric modules but also comparable to those of commercial thermoelectric modules utilizing the Seebeck effect. The multifunctionality of our MCM provides unprecedented opportunities for energy harvesting and thermal management everywhere permanent magnets are currently used.