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

Recently, low-cost Mg3Sb2-yBiy-based materials with high performance near room temperatures have been reported, which are considered to be promising candidates for replacing commercial Bi2Te3-based materials. Herein, we report a high power factor of similar to 3000 mu W m(-1) K-1 and a ZT value of 0.82 at room temperature in Ti0.05Mg3.15Sb1.5Bi0.49Te0.01. 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 degree celsius, 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 degree celsius and 500 degree celsius with T-c = 0 degree celsius, respectively, demonstrating the great potential of substituting the commercial Bi2Te3-family.