Exceptional thermoelectric performance in AB2Sb2-type Zintl phases through band shaping

Abstract

Advanced thermoelectric technology requires high-performance materials with exceptional electrical performance for large power output during service. AB₂Sb₂-type Zintl phases, especially Mg₃Sb₂, have attracted great attention recently because of the advantages of high-performance, low-cost and nontoxic components. Currently, remarkably high thermoelectric figures of merit zT values of 1.7–1.9 are reported in n-type Mg₃Sb₂-based materials, but they are quite low in p-type materials because of the small valence band degeneracy N_v and relatively high band effective mass . Here, we propose a band shaping strategy to effectively enhance the material's electrical transports. Through alloying Zn at the Mg2 sites of Mg₃Sb₂, double band degeneracy is achieved. Further alloying Yb at the Mg1 sites, band edge effective mass is greatly reduced. Combining the optimized carrier concentration by Li doping, the maximum power factor and zT values are increased to 15.9 μW cm⁻¹ K⁻² and 1.4, respectively, superior to those of the vast majority of reported p-type AB₂Sb₂ Zintl phases. This work demonstrates that band edge shaping is very successful for the optimization of electrical transport and thermoelectric performance in semiconductors.