Improved thermoelectric performance of BiCuSeO by Ag substitution at Cu site
BiCuSeO oxyselenide-based thermoelectric materials are attracting much attention due to their ultra-low intrinsic thermal conductivity (ĸ) and moderate Seebeck coefficient (S). However, the low conversion efficiency limits their application in energy conversion systems. This paper investigated the effect of monovalent Ag-doping in BiCuSeO at Cu site in the presence of polyvinyl alcohol (PVA). The results show that Ag is effectively doped at Cu site. The heavy atom substitution in BiCu1−xAgxSeO at Cu site can enhance S and reduce its total thermal conductivity (k) by phonon scattering. Further, the incorporation of heavy atom (Ag) with different ionic radii results in the improved ZT of 0.64 for BiCu1−xAgxSeO, which is 16% more than that for pure BiCuSeO (ZT = 0.55) at 923 K. It is believed that the Cu site should be an efficient dopant site to improve the efficiency of oxyselenide-based thermoelectric materials.