Excellent Room Temperature Thermoelectric Performance in Mg₃Sb₂-Based Alloys via Multi-Functional Doping of Nb

Mg₃Sb₂-based alloys are attracting increasing attention due to the excellent room temperature thermoelectric properties. However, due to the presence and easy segregation of charged Mg vacancies, the carrier mobility in Mg₃Sb₂-based alloys is always severely compromised that significantly restricts the room temperature performance. General vacancy compensation strategies cannot synergistically optimize the complicated Mg₃Sb₂ structures involving both interior and boundary scattering. Herein, due to the multi-functional doping effect of Nb, the electron scattering inside and across grains is significantly suppressed by inhibiting the accumulation of Mg vacancies, and leading to a smooth transmission channel of electrons. The increased Mg vacancies migration barrier and optimized interface potential are also confirmed theoretically and experimentally, respectively. As a result, a leading room temperature zT of 1.02 is achieved. This work reveals the multi-functional doping effect as an efficient approach in improving room temperature thermoelectric performance in complicated defect/interface associated Mg₃Sb₂-based alloys.