Evolution of Nanometer-Scale Microstructure within Grains and in the Intergranular Region in Thermoelectric Mg(Sb, Bi) Alloys.

n-type MgSb-MgBi alloys have been investigated as one of the most promising thermoelectric materials. To achieve high performance, a detailed understanding of the microstructure is required. Although MgSb-MgBi is usually considered to be a complete solid solution, nanosized compositional fluctuations were observed within a matrix and in the vicinity of the grain boundary.

Metallic n-Type Mg Sb Single Crystals Demonstrate the Absence of Ionized Impurity Scattering and Enhanced Thermoelectric Performance.

Mg (Sb,Bi) alloys have recently been discovered as a competitive alternative to the state-of-the-art n-type Bi (Te,Se) thermoelectric alloys. Previous theoretical studies predict that single crystals Mg (Sb,Bi) can exhibit higher thermoelectric performance near room temperature by eliminating grain boundary resistance. However, the intrinsic Mg defect chemistry makes it challenging to grow n-type Mg (Sb,Bi) single crystals.

Improvement of Low-Temperature zT in a Mg Sb -Mg Bi Solid Solution via Mg-Vapor Annealing.

Materials with high zT over a wide temperature range are essential for thermoelectric applications. n-Type Mg Sb -based compounds have been shown to achieve high zT at 700 K, but their performance at low temperatures (<500 K) is compromised due to their highly resistive grain boundaries. Syntheses and optimization processes to mitigate this grain-boundary effect has been limited due to loss of Mg, which hinders a sample's n-type dopability.