High figure-of-merit in Zn, Sb co-doped Mg2Si0.3Sn0.7 alloy through simultaneous optimization of electrical and thermal transports

The derivatives of Mg₂Si have recently attracted wide attention as promising thermoelectric materials due to earth abundant and environment friendly low-cost constituents. The main challenge in optimizing the thermoelectric figure of merit ZT, is the low electrical and high thermal conductivities of Mg₂Si. The present study demonstrates high ZT of ∼1.55 at 673 K in Mg₂Si_0.3Sn_0.7 through simultaneous optimization of electrical and thermal transport through Sb and Zn co-doping. The ultra-low deformation and alloy scattering potentials in Sb and Zn co-doped samples helps in maintaining record high Hall mobility ∼70–90 cm²/V.s. The doping induced pudding mold band structure with hyperconvergence in conduction band balances high Seebeck coefficient and high electrical conductivity. The point defects and dislocations created by doping helps in lowering of lattice thermal conductivity as well. The uni-leg power generator fabricated using optimized Mg_1.96Zn_0.04(Si_0.3Sn_0.7)_0.98Sb_0.02 exhibits a record efficiency of ∼9.5 % at ΔT ∼ 329 K.