Highly Effective Solid Solution towards High Thermoelectric and Mechanical Properties in Cu₃SbSe₄-Cu₂GeSe₃ Bulk...

In the pursuit of high-performance thermoelectric materials, the challenge often lies in achieving high doping concentrations, which are essential for enhancing electrical properties. Traditional doping methods may prove insufficient, as the solid solution effect is not optimal. In this study, we introduce a doping approach termed "quasi-homogenization". This doping strategy utilizes two structurally and compositionally similar compounds, allowing for a more efficient solid solution of Ge in Cu₃SbSe₄.This approach demonstrates superior efficiency compared to prior endeavors aimed at optimizing the thermoelectric properties of Cu₃SbSe₄ through Ge doping. The efficient solid solution of Ge not only provides a substantial number of carriers, thereby enhancing the electrical properties of the material, but also induces notable changes in its microstructure. Following Ge solid solution, the material exhibits increased porosity and reduced grain size, dislocations and second phase generation. These structural modifications contribute to a significant reduction in the lattice thermal conductivity of the material. In the Cu₃SbSe₄ + 1.0 wt % Cu₂GeSe₃ sample, a peak ZT of 1.0 was attained at 723 K, while an average ZT of 0.56 was achieved within the temperature range of 323 to 723 K. Furthermore, nanoindentation tests revealed a significant enhancement in the mechanical properties of the material, evidenced by a 10% increase in hardness and a 6% increase in modulus. This work underscores the feasibility of enhancing the efficient solid solution of ternary elements through "quasi-homogenization", a doping method that holds promise for broader applications across various ternary systems.