Boosting room-temperature thermoelectric performance of Mg3Sb1.5Bi0.5 material through breaking the contradiction between carrier concentration and carrier mobility

Recently, low-cost Mg ₃Sb _{2- y}Bi _y-based materials with high performance near room temperatures have been reported, which are considered to be promising candidates for replacing commercial Bi ₂Te ₃-based materials. Herein, we report a high power factor of ∼3000 μW m ⁻¹ K ⁻¹ and a ZT value of 0.82 at room temperature in Ti _0.05Mg _3.15Sb _1.5Bi _0.49Te _0.01 . Ti dopant entering into the Mg1 sublattice slightly increases the carrier concentration by the introduction of impurity states and enhances the carrier mobility by the promotion of grain size growth. The two-donor doping strategy breaks the contradiction between carrier concentration and carrier mobility, thus significantly improving the electrical transport properties near room temperatures. In addition, the introduction of defects by Ti dopant contributes to the decreased lattice thermal conductivity. Consequently, a ZT_avg value of 1.19 is obtained at 50–250 ℃, ranking the top among reported n-type thermoelectric materials. Moreover, the as-fabricated single-leg device shows an high engineering efficiency considering the radiation calibration, i.e., 7.2 % and 11.8 % at temperature differences of 250 ℃ and 500 ℃ with T_c = 0 ℃, respectively, demonstrating the great potential of substituting the commercial Bi ₂Te ₃-family.