Enhanced Thermoelectric Performance of Vertical Bridgman-Grown Mg 2 Si by Codoping with Sb and Zn

To improve the thermoelectric (TE) performance of Mg 2 Si by optimizing the carrier concentration and reducing thermal conductivity, we focus on codoping Sb and Zn using theoretical and experimental methods. First-principles calculations show that Sb is a stable and controllable n -type dopant for Mg 2 Si, whereas Zn considerably shrinks the Mg 2 Si cell. We fabricate dense and high-purity polycrystalline Mg 2 M x Si (M = Sb, Zn; x = 0, 0.1, 0.3, and 0.5 at.%) via the all-melt process of the conventional vertical Bridgman (VB) method and examine the influence of dilute codoping of Sb and Zn on the TE properties of Mg 2 Si. VB-grown Mg 2 Si doped with 0.5 at.% Zn and Sb shows higher electrical conductivity than pure Mg 2 Si, achieving an increased power factor by 4.62–15.23% over that of the sintered specimen under the same doping rate at 323–873 K. Because the decreased lattice thermal conductivity of the codoped specimens nullifies the increased electronic thermal conductivity, the total thermal conductivity is similar to that of pure Mg 2 Si. Consequently, the dimensionless figure of merit of VB-grown Mg 2 Si doped with 0.5 at.% Zn and Sb reaches 0.82 at 873 K. Graphical Abstract