LAUSR

As an environmentally friendly thermoelectric material with its constituents being free of Pb/Te, tetrahedrite Cu12Sb4S13 absorbs much research interest. However, its low thermoelectric performance inhibits its applications. Here, we show that through dual substitution of Se for S and Zn for Cu in the compound, both the electrical conductivity and the thermopower are enhanced, leading to the elevation of the power factor as high as ∼33% (at 723 K). Analyses indicate that the substitution of Se for S gives rise to changes in stoichiometry of Cu12Sb4S13 through precipitation of impurity phase Cu3SbS4, which causes variations of S vacancies and hole concentrations, while Zn2+ substitution for Cu1+ introduces donors, both of which tune and optimize the carrier concentration. Besides, the lattice thermal conductivity of dual substituted samples is reduced by as low as ∼30% (at 723 K) due to intensified phonon scattering of the impurities (Se and Zn). As a result, a large figure of merit ZT = 0.9 (at 723 K) is achieved in Cu12−yZnySb4S12.8Se0.2 samples with y = 0.025 and 0.05, which is ∼41% higher than that of pristine tetrahedrite Cu12Sb4S13, indicating that dual substitution is an effective approach to improving its thermoelectric performance.