N-Type Mg <sub>3</sub> Sb <sub> 2- <i>x</i> </sub> Bi <i> <sub>x</sub> </i> Alloys as Promising Thermoelectric Materials
Hongjing Shang, Zhongxin Liang, Congcong Xu, Jun Mao, Hongwei Gu, Fazhu Ding, Zhifeng Ren
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 ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi>z</mml:mi> <mml:mi>T</mml:mi> </mml:math> ), 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.