Enhancing thermoelectric performance in P-Type Mg3Sb2-based zintls through optimization of band gap structure and nanostructuring

P-type Mg3Sb2-based Zintls have attracted considerable interest in the thermoelectric (TE) field due to their environmental friendliness and low cost. However, compared to their n-type counterparts, they show relatively low TE performance, limiting their application in TE devices. In this work, we simul-taneously introduce Bi alloying at Sb sites and Ag doping at Mg sites into the Mg3Sb2 to coopera-tively optimize the electrical and thermal properties for the first time, acquiring the highest ZT value of & SIM;0.85 at 723 K and a high average ZT of 0.39 in the temperature range of 323-723 K in sample Mg2.94Ag0.06Sb1.9Bi0.1. The first-principle calculations show that the co-doping of Ag and Bi can shift the Fermi level into the valence band and narrow the band gap, resulting in the increased carrier concentration from 3.50 x 10 17 cm -3 in the reference Mg3Sb0.9Bi0.1 to & SIM;7.88 x 10 19 cm -3 in sample Mg2.94Ag0.06Sb0.9Bi0.1. As a result, a remarkable power factor of & SIM;778.9 & mu;W m -1 K -2 at 723 K is achieved in sample Mg2.94Ag0.06Sb0.9Bi0.1. Meanwhile, a low lattice thermal conductivity of & SIM;0.48 W m -1 K -1 at 723 K is also obtained with the help of phonon scattering at the distorted lattice, point defects, and nano-precipitates in sample Mg2.94Ag0.06Sb0.9Bi0.1. The synergistic effect of using the multi-element co-doping/-alloying to optimize electrical properties in Mg3Sb2 holds promise for further improving the TE performance of Zintl phase materials or even others.& COPY; 2023 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.