Enhanced Thermoelectric Performance of Sn-Doped Permingeatites Cu3Sb1-ySnySe4

Abstract

In this study, Cu3Sb1-ySnySe4 (0 ≤ y ≤ 0.08) permingeatites were synthesized via mechanical alloying followed by hot pressing. The phase transformation, microstructure, charge transport parameters of the permingeatites, and their thermoelectric properties were analyzed. The permingeatites were present in a single phase with a tetragonal structure, and secondary phases were not detected. The permingeatites had relative densities of 97.2%–98.5%. The lattice constants of the a- and c-axis increased when Sn was substituted at the Sb sites. With increasing Sn content, the carrier concentration increased to (2.2–4.1) × 10<sup>19</sup> cm<sup>-3</sup>; however, mobility did not change significantly, at 58–66 cm<sup>2</sup>V<sup>-1</sup>s<sup>-1</sup>. The undoped Cu3SbSe4 behaved as a non-degenerate semiconductor. Its Lorenz number was calculated to be (1.57–1.56) × 10<sup>-8</sup>V<sup>2</sup>K<sup>-2</sup> at 323–623 K, and a maximum dimensionless figure of merit (<i>ZT</i>) of 0.39 was obtained at the temperature of 623 K, power factor of 0.49 mWm<sup>-1</sup>K<sup>-2</sup>, and thermal conductivity of 0.76 Wm<sup>-1</sup>K<sup>-1</sup>. However, the Sn-doped specimens behaved as degenerate semiconductors. Their Lorenz numbers increased to (1.63–1.94) × 10<sup>-8</sup>V<sup>2</sup>K<sup>-2</sup> at 323–623 K. Cu3Sb0.96Sn0.04Se4 exhibited a remarkably enhanced <i>ZT</i> of 0.71 at a temperature of 623 K, power factor of 1.18 mWm<sup>-1</sup>K<sup>-2</sup>, and thermal conductivity of 1.01 Wm<sup>-1</sup>K<sup>-1</sup>.