Enhancing thermoelectric and mechanical properties of p-type Cu₃SbSe₄-based materials via embedding nanoscale Sb₂Se₃

Cu₃SbSe₄, a promising p-type thermoelectric (TE) material consisting of earth-abundant, nontoxic, cost-efficient and eco-friendly constituent elements. However, its low TE performance is relatively poor because of the low carrier concentration and mobility. Herein, we synergistically optimize the electrical and thermal transport properties of Cu₃SbSe₄ via embedding nanoscale Sb₂Se₃. The Sb₂Se₃ nanophase markedly increases the carrier concentration and carrier effective mass simultaneously, resulting in a higher power factor of ∼1100 μW m⁻¹ K⁻². Surprisingly, Sb₂Se₃ nanophase induces high-density phase boundaries and dislocations, which significantly depress the lattice thermal conductivity. The multiple effects of incorporation of Sb₂Se₃ boost Cu₃SbSe₄ to an outstanding ZT value of ∼0.86 at 673 K for Cu₃SbSe₄ +1.5 mol% Sb₂Se₃ composite, which is ∼1.70 times as high as that of pristine Cu₃SbSe₄. It is highly remarkable that Cu₃SbSe₄ with nanoscale Sb₂Se₃ is mechanically robust, showing the Vickers hardness (H_v) and fracture toughness (K_IC) of ∼2.54 GPa and ∼0.73 ± 0.02 MPa m^½, which are ∼20% and ∼12% higher than those of pristine Cu₃SbSe₄, respectively. This work provides guidance for enhancing the comprehensive TE and mechanical properties of the copper-based chalcogenides by embedding nanophases.