Influence of group Ш elements doping on thermoelectric properties of Mg3Sb1.5Bi0.5 alloy

[Display omitted] •Defect formation energy of Sc-, Y-, and Mg-doped Mg3Sb1.5Bi0.5 alloys are determined.•Contribution of doping elements to the carrier effective mass is achieved.•Sc-doped alloy depicted optimal electronic transport performances.•The top value of ZT reached 1.21 at T = 700 K for Y-doped Mg3Sb1.5Bi0.5 alloy. Some studies have shown that the performance of Mg3Sb1.5Bi0.5 alloys can further be optimized through donor doping. Accordingly, the first-principles calculations and directional solidification methods were used in this work to analyze the defect formation energies and electronic structures of alloys containing Sc, Y, and Al substituting different Mg sites. Sc and Y elements changed the carrier effective mass, leading to optimized Seebeck coefficient. The doped Sc atoms resulted in a balanced influence on the Seebeck coefficient and carrier mobility. The doped Al atoms illustrated a stronger scattering effect on phonons, leading to the lowest lattice thermal conductivity. The significant electronic transport performance of Sc and Y-doped alloys resulted in higher values of the figure of merit at low (T 450 K) temperatures, respectively. Overall, significant reference data for optimizing the thermoelectric performance of n-type Mg3(Sb, Bi)2-based materials by doping method were provided.