Effect of Elemental Magnesium on the Interfacial Thermal Stability of Mg ₃ Sb _1.5 Bi _0.5 -Based Thermoelectric Devices

Thermoelectric technology converts low-grade waste heat into electrical energy, offering an environmentally sustainable pathway for global development. N-type Mg 3 (Sb, Bi) 2 thermoelectric materials have garnered significant attention due to their outstanding thermoelectric performance over broad temperatures (27–500 °C). However, unavoidable Mg loss and interfacial element diffusion degrade the performance and service life of thermoelectric devices, thereby limiting the application of thermoelectric technology. Here, we introduce elemental Mg into thermoelectric interfacial materials (TEiMs) to suppress harmful Mg diffusion and compensate for Mg loss within the material, achieving dual stability in Mg 3 (Sb, Bi) 2 devices. After 30 days of aging, Mg 3 (Sb, Bi) 2 single-arm devices maintained an outstanding power density of 0.75 W/cm 2 and a remarkable conversion efficiency of 8.9%, demonstrating unprecedented stability. These findings offer design strategies for TEiMs and provide valuable references for interface engineering in diverse thermoelectric systems, thereby advancing the practical feasibility of thermoelectric energy harvesting in renewable energy and waste heat applications.