Enhanced Thermoelectric Properties of Cu_3SbSe_4 Compounds by Isovalent Bismuth Doping

摘要

Cu_3SbSe_4, featuring its earth-abundant, cheap, nontoxic and environmentally friendly constituent elements, can be considered as a promising intermediate temperature thermoelectric (TE) material. Herein, a series of p-type Bi-doped Cu_3Sb_(1-x)Bi_xSe_4 (x = 0-0.04) samples were fabricated through melting and hot pressing process, and the effects of isovalent Bi-doping on their TE properties were comparatively investigated by experimental and computational methods. TEM analysis indicates that Bi-doped samples consist of Cu_3SbSe_4 and Cu_(2-x)Se impurity phases, which is in good agreement with the results of XRD, SEM and XPS. For Bi-doped samples, the reduced electrical resistivity (ρ) caused by the optimized carrier concentrations and enhanced Seebeck coefficient derived from the densities of states near the Fermi level give rise to a high power factor of ～ 1000 μWm~(-1) K~(-2) at 673 K for the Cu_3Sb_(0.985)Bi_(0.015)Se_4 sample. Additionally, the multiscale defects of Cu_3SbSe_4-based materials involving point defects, nanoprecipitates, amorphous phases and grain boundaries can strongly scatter phonons to depress lattice thermal conductivity (K_(lat))/resulting in a low K_(lat) of ～ 0.53 Wm~(-1) K~(-1) and thermal conductivity (K_(tot)) of ～ 0.62 Wm~(-1) K~(-1) at 673 K for the Cu_3Sb_(0.98)Bi_(0.02)Se_4 sample. As a consequence, a maximum ZT value ～ 0.95 at 673 K is obtained for the Cu_3Sb_(0.985)Bi_(0.015)Se_4 sample, which is ～ 1.9 times higher than that of pristine Cu_3SbSe_4. This work shows that isovalent heavy element doping is an effective strategy to optimize thermoelectric properties of copper-based chalcogenides.