High-Performance N-type Mg₃Sb₂ towards Thermoelectric Application near Room Temperature

Se-doped Mg_3.2Sb_1.5Bi_0.5-based thermoelectric materials are revisited in this study. An increased ZT value ≈1.4 at about 723 K is obtained in Mg_3.2Sb_1.5Bi_0.49Se_0.01 with optimized carrier concentration ≈1.9 × 10¹⁹ cm⁻³. Based on this composition, Co and Mn are incorporated for the manipulation of the carrier scattering mechanism, which are beneficial to the dramatically enhanced electrical conductivity and power factor around room temperature range. Combined with the lowered lattice thermal conductivity due to the introduction of effective phonon scattering centers in Se&Mn-codoped sample, a highest room temperature ZT value ≈0.63 and a peak ZT value ≈1.70 at 623 K are achieved for Mg_3.15Mn_0.05Sb_1.5Bi_0.49Se_0.01, leading to a high average ZT ≈1.33 from 323 to 673 K. In particular, a remarkable average ZT ≈1.18 between the temperature of 323 and 523 K is achieved, suggesting the competitive substitution for the commercialized n-type Bi₂Te₃-based thermoelectric materials.