Enhanced thermoelectric performance of Mg3Sb2-xBix thermoelectric thin films through carrier concentration modulation by Bi alloying

Abstract

Mg3Sb2-based alloys exhibit promising characteristics as thermoelectric materials owing to their non-toxicity, low cost, abundance of earth constituent elements, and high thermoelectric performance. However, the thermoelectric performance of Mg3Sb2-based films remains challenging due to their inherently low carrier concentration. To address this challenge, this work focuses on elevating the carrier concentration of Mg3Sb2-xBix films via alloying Bi in Mg3Sb2. The results demonstrate that the incorporation of the Bi element successfully increases the carrier concentration of Mg3Sb2-xBix (x=0, 0.5, 1.5, and 2) films from 1016 cm−3 (x=0) to 1020 cm−3 (x=2). Furthermore, the introduction of Bi in Mg3Sb2-xBix films suppresses the phonon transport by enhancing boundary scattering of phonon, leading to a decrease in thermal conductivity. Ultimately, the synergistic optimization drives the peak ZT value to 0.27 for x=1.5 in Mg3Sb2-xBix at 525 K, which is more than seven times higher compared to the Mg3Sb2 thin film (ZT ∼0.035 at 525 K). This work has improved the thermoelectric properties of Mg3Sb2-based films, making an essential contribution to the advancement of Mg3Sb2-based film materials in the field of Micro-thermoelectric devices.