N-Type Mg ₃ Sb _{2- x} Bi _x Alloys as Promising Thermoelectric Materials

Abstract

N-type Mg3Sb2-xBix alloys have been extensively studied in recent years due to their significantly enhanced thermoelectric figure of merit (zT), thus promoting them as potential candidates for waste heat recovery and cooling applications. In this review, the effects resulting from alloying Mg3Bi2 with Mg3Sb2, including narrowed bandgap, decreased effective mass, and increased carrier mobility, are summarized. Subsequently, defect-controlled electrical properties in n-type Mg3Sb2-xBix 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 Mg3Sb2-xBix thermoelectric materials. Finally, we review the present status of, and future outlook for, these materials in power generation and cooling applications.

Maximizing the performance of n-type Mg3Bi2 based materials for room-temperature power generation and thermoelectric cooling

“…However, one of the main reasons that limit its further wide applications is the scarcity of Tellurium (Te) element. During the past decade, some new Te-free thermoelectric candidates with high zTs, such as α-MgAgSb [22][23][24] , Mg 3 Bi 2 [25][26][27][28][29][30] , SnSe 31,32 , enable the potential replacement of Bi 2 Te 3 , in which a high power-generation performance of Mg 3 Sb 2 / MgAgSb module, with the target for harvesting low-temperature waste heat, has already been demonstrated very recently 33,34 . P-type α-MgAgSb shows the large enhancement of thermoelectric performance at the low-temperature range by suitable doping 22,35 .…”

Realizing High Thermoelectric Performance in N‐Type Mg3(Sb, Bi)2‐Based Materials via Synergetic Mo Addition and Sb–Bi Ratio Refining

“…Mg 3 Sb 2 , which crystalizes in CaAl 2 Si 2 -type structure, consists of a tetrahedrally coordinated anion [Mg 2 Sb 2 ] 2− layer and octahedrally coordinated cation Mg 2+ layer stacked in the z direction, [36,40] which contributes to the excellent electrical properties and intrinsically low 𝜅 lat . Considering the design principles of GB segregation explored in previous reports, when the added element is far from the host in the periodic table, then the oversized or undersized atom prefers to modify in-terfaces in various ways.…”

Perspective— Powerful Micro/Nano-Scale Heat Engine: Thermoelectric Converter on Chip

“…Besides, the trend of thermoelectric materials is to develop new material systems containing cheap and earthabundant elements, such as the recently emerged Mg(Sb,Bi)-based materials to replace Te. 10 The development of organic thermoelectric materials enables devices flexible. However, the zT value of the organic material systems is generally lower than that of the inorganic material, and its stability faces challenges.…”