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

Additional cation doping is one of the potential strategies to enhance the thermoelectric (TE) performance of Mg 3 Sb 2 -based materials with precise regulation of interaction between cations and the host. In this work, using Mg 3 Sb 1.5 Bi 0.5 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 Mg 3.2 Y 0.04 La 0.01 Sb 1.5 Bi 0.5 . 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 .