Thermoelectric enhancement achieved by Y and La Co-doping in n-type Mg3.2Sb1.5Bi0.5

Abstract

Additional cation doping is one of the potential strategies to enhance the thermoelectric (TE) performance of Mg3Sb2-based materials with precise regulation of interaction between cations and the host. In this work, using Mg3Sb1.5Bi0.5 as an example, we confirmed that co-doping rare-earth elements with Y and La is capable to simultaneously improve its power factor and suppress the thermal conductivity: Y is an effective n-type dopant to regulate the optimal carrier concentration, while La doping can modulate the band structure and increase the effective mass that related to the improved Seebeck coefficient. A promising power factor of 18.3 μW cm-1 K-2 is obtained after co-doping. Meanwhile, the lattice thermal conductivity is dramatically reduced to 0.39 W m-1 K-1 at 750 K thanks to the extra defect scattering introduced by Y and La. As a result, a peak figure of merit (zT) of 1.76 and a competitive average zT of 1.1 among 300–750 K are achieved in Mg3.2Y0.04La0.01Sb1.5Bi0.5. The synergistic effect stemming from dual-cations doping provides profound insights for controllable host-dopant design and modulation toward high-efficient n-type TE materials.