Amorphous carbon nano-inclusions for strategical enhancement of thermoelectric performance in Earth-abundant Cu₃SbS₄

Cu₃SbS₄ is an effective, low cost and non-toxic thermoelectric compound for intermediate temperature applications. However, its tetragonal structure needs to be tuned for efficient phonon scattering to reduce thermal conductivity and enhance zT. In this present article, the semiconductive carbon black nano-inclusions effect on Cu₃SbS₄ thermoelectric performance is studied. The thermoelectric properties of the fabricated samples are investigated in the temperature range of 300–623 K. Addition of amorphous carbon nano-inclusions in Cu₃SbS₄ causes a reduction in the thermal conductivity by phonon scattering and improvement in the Seebeck coefficient by carrier energy filtering mechanisms. The maximum figure of merit of 0.51 is obtained for 3 mol.% carbon nano-inclusion sample at 623 K. Additionally, enhancement of thermal stability and mechanical stability (hardness) with increased carbon nano-inclusion concentration is observed. It is found that grain boundary hardening and dispersion strengthening are the reasons for the enhancement. Moreover, our detailed studies demonstrate that the addition of carbon nano-inclusions in Cu₃SbS₄ can produce efficient, non-toxic, and inexpensive state-of-the-art thermoelectric devices.