2, Shanghai University, Shanghai, , China
3, Tsinghua University, Beijing, , China
BiCuSeO-based materials are promising thermoelectrics for intermediate temperatures, primarily due to their ultralow lattice thermal conductivity. The intrinsically low carrier mobility in these materials, however, largely limits further improvements of their thermoelectric properties. In this talk, we show that the electrical transport properties of these materials can be enhanced by increasing the chemical bond covalency in the Cu-Se layer, and by rationally utilizing the multi-valley electronic band structure. High thermoelectric figure of merit ZT values of 1.2-1.3 can be achieved at 873 K. All samples were synthesized by nonequilibrium self-propagating high-temperature synthesis (SHS) processes. The resulting hierarchical structural features lead to lattice thermal conductivity values close to the amorphous limit.