Charge Transport and Thermoelectric Properties of Mn-Doped Tetrahedrites Cu12-xMnxSb4S13

Abstract

Mn-doped tetrahedrites Cu12-xMnxSb4S13 (0.1 ≤ x ≤ 0.4) were synthesized by mechanical alloying (MA) and sintered by hot pressing (HP). A single tetrahedrite phase was synthesized by MA without post-annealing, and it was stable without any phase changes after HP. The hot-pressed specimens had a relative density higher than 98.6%. The lattice constant of the Mn-doped samples increased compared to that of undoped Cu12Sb4S13, but no significant change in the lattice constant was observed with a change in Mn content. All Mn-doped tetrahedrites acted as p-type semiconductors, as confirmed from positive Hall and Seebeck coefficient values. The Seebeck coefficient increased with increasing temperature but decreased with increasing Mn content; maximum Seebeck coefficient values of 200−219 μVK-1 were obtained at 323−723 K for x = 0.1. Electrical conductivity increased with increasing temperature and Mn content; the highest electrical conductivity values of (1.76−2.45) × 104 Sm-1 were obtained at 323−723 K for x = 0.4. As a result, Cu11.6Mn0.4Sb4S13 exhibited a maximum power factor of 0.80 mWm-1K-2 at 723 K. As the Mn content increased, both the electronic and lattice thermal conductivities increased, and thus, the total thermal conductivity was the lowest at 0.48–0.63Wm-1K-1 at 323–723 K for x = 0.1. A maximum dimensionless figure of merit of 0.75 was obtained at 723 K for Cu11.7Mn0.3Sb4S13. The MA-HP process is suitable for preparing doped tetrahedrites exhibiting excellent thermoelectric performance.