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

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 10(16) cm(-3) (x=0) to 10(20) 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 similar to 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