Ultralow Thermal Conductivity and Extraordinary Thermoelectric Performance Realized in Codoped Cu3SbSe4 by Plasma Spark Sintering

Cu₃SbSe₄-based materials have attracted much attention for thermoelectric power generation in the mid-temperature range due to their low cost, ecofriendliness, and abundant elements on the earth. However, the peak figure of merit (ZT) for the Cu₃SbSe₄-based system prepared by the fusion method is usually smaller than unity because of its high thermal conductivity. Here, we show that through a coprecipitation method combined with spark plasma sintering ultrafine-grained Cu₃Sb_0.94Sn_0.06Se_4-yS_y (y = 0, 0.5) embedded with Cu₃SbSe₃ nanoprecipitates can be prepared. Due to the ultralow thermal conductivity and enhanced Seebeck coefficient, a record-high ZT value of 1.32 is achieved for the sample Cu₃Sb_0.94Sn_0.06Se_3.5Se_0.5. The ultralow thermal conductivity is attributed to the enhanced phonon scattering caused by the nanoprecipitates and fine grains of the samples, and the improved Seebeck coefficient originates from the enhancement of electronic density-of-state effective mass. Present results demonstrate that excellent thermoelectric performance can be realized in dual-substituted and fine-grained Cu₃Sb_0.94Sn_0.06Se_4-yS_y with nanoprecipitates.