N-Type Mg 3 Sb 2- x Bi x Alloys as Promising Thermoelectric Materials

Abstract

N-type Mg 3 Sb 2- x Bi x alloys have been extensively studied in recent years due to their significantly enhanced thermoelectric figure of merit ( z T ), thus promoting them as potential candidates for waste heat recovery and cooling applications. In this review, the effects resulting from alloying Mg 3 Bi 2 with Mg 3 Sb 2 , including narrowed bandgap, decreased effective mass, and increased carrier mobility, are summarized. Subsequently, defect-controlled electrical properties in n-type Mg 3 Sb 2- x Bi x are revealed. On one hand, manipulation of intrinsic and extrinsic defects can achieve optimal carrier concentration. On the other hand, Mg vacancies dominate carrier-scattering mechanisms (ionized impurity scattering and grain boundary scattering). Both aspects are discussed for Mg 3 Sb 2- x Bi x thermoelectric materials. Finally, we review the present status of, and future outlook for, these materials in power generation and cooling applications.