Enhanced thermoelectric performance of p -type Mg 3 Sb 2 by lithium doping and its tunability in an anionic framework

Mg3Sb2-based Zintl compounds are considered as promising thermoelectric materials due to their low thermal conductivity and high Seebeck coefficient. In this paper, we studied the thermoelectric properties of p-type lithium (Li)-doped Mg3Sb2 prepared by ball milling and hot pressing. A maximum ZT value ~ 0.6 at about 773 K was achieved in Mg2.975Li0.025Sb2, which was ascribed to the increased carrier concentration by Li doping. Mixed scattering mechanism is dominated at lower temperature, yielding higher carrier mobility. Isoelectronic substitution of Zn on the Mg site further increased the electrical conductivity by narrowing the band gap and decreased the lattice thermal conductivity by double substitution, contributing to an enhanced average ZT in Mg2.475Zn0.5Li0.025Sb2.