Enhanced thermoelectric performance in n-type Mg3.2Sb1.5Bi0.5 doping with lanthanides at the Mg site

Abstract

• Gd and Ho have increased the DOS of the valence band near the Fermi level, and the d electrons of Gd and Ho have made extraordinary contributions. • Gd and Ho are effective n-type cation site dopants with higher doping efficiency and better carrier concentration than the anion site dopants chalcogenide elements. • For Mg 3.2 Gd 0.02 Sb 1.5 Bi 0.5 and Mg 3.2 Ho 0.02 Sb 1.5 Bi 0.5 samples, we obtain high zT values of 1.61 and 1.55 at 725 K, respectively. • Gd as well as Ho are an alternative effective n-type doping element for higher thermoelectric performance. Mg-based thermoelectric materials have attracted more and more attention because of their rich composition elements, green environmental protection, and lower price. In recent years, the thermoelectric properties of n-type Mg 3 Sb 2 materials have been optimized by doping chalcogenide elements (S, Se, and Te) at the anionic position. In this work, n-type Mg 3.2 A x Sb 1.5 Bi 0.5 ( A = Gd, Ho; x = 0.01, 0.02, 0.03, and 0.4) samples were prepared by the cation site doping of lanthanide elements (Gd and Ho). The research results show that Gd and Ho doped n-type Mg 3.2 Sb 1.5 Bi 0.5 samples are entirely comparable to the S, Se, and Te doped n-type Mg 3.2 Sb 1.5 Bi 0.5 samples, demonstrating more excellent thermoelectric properties. Doping with lanthanides (Gd and Ho) at the Mg site increases the carrier concentration of the material to 8.161 × 10 19 cm −3 . Doping induces the contribution of more electron, thus obtaining higher conductivity. The maximum zT value of the Mg 3.2 Gd 0.02 Sb 1.5 Bi 0.5 and the Mg 3.2 Ho 0.02 Sb 1.5 Bi 0.5 samples reaches 1.61 and 1.55, respectively. This work theoretically and experimentally demonstrates Gd and Ho are efficient n-type dopants for Mg 3.2 Sb 1.5 Bi 0.5 thermoelectric material.