Rapid one-step synthesis and compaction of high-performance n-type Mg3Sb2 thermoelectrics

Abstract

n-type Mg3Sb2-based compounds are emerging as a promising class of low-cost thermoelectric materials due to their extraordinary performance at low and intermediate temperatures. However, so far high thermoelectric performance has merely been reported in n-type Mg3Sb2-Mg3Bi2 alloys with a large amount of Bi. Moreover, current synthesis methods of n-type Mg3Sb2 bulk thermoelectrics involve multi-step processes that are time- and energy-consuming. Here we report a fast and straightforward approach to fabricate n-type Mg3Sb2 thermoelectrics using spark plasma sintering, which combines the synthesis and compaction in one step. Using this method, we achieve a high thermoelectric figure of merit zT of ~0.4-1.5 at 300-725 K in n-type (Sc, Te)-doped Mg3Sb2 without alloying with Mg3Bi2. In comparison with the currently reported synthesis methods, the complexity, process time, and cost of the new method are significantly reduced. This work demonstrates a simple, low-cost route for the potential large-scale production of n-type Mg3Sb2 thermoelectrics.