Synthesis-temperature-dependent phase composition manipulation toward high thermoelectric performance in tetrahedrites

Tetrahedrite, an Earth-abundant natural mineral, has attracted extensive research interest because of its excellent thermoelectric performance. Herein, tetrahedrite samples comprising Cu-poor Cu12Sb4S13 and Cu-rich Cu14Sb4S13 phases have been synthesized using a colloidal method, in which the ratio of two phases is manipulated by controlling the synthesis temperature to improve the thermoelectric performance. It is found that an ultralow total thermal conductivity of ∼0.3 W m−1 K−1 at 723 K is realized in the sample with a Cu-rich phase fraction of ∼50%, which can be attributed to maximized phonon scattering by phase boundaries. As a result, combined with a decent power factor, this sample obtains an optimal zT of 1.15, which is about 85% higher than that of the sample with a Cu-rich phase fraction of ∼64% and comparable to zT values of other eco-friendly, abundant Cu-based thermoelectric materials. This work demonstrates an effective synthesis-temperature-dependent phase composition manipulation strategy toward enhanced thermoelectric performance in tetrahedrites.