Low thermal conductivity and high thermoelectric performance in Cu₂Se/CuAgSe composite materials

As a typical superionic conductor, Cu₂Se has attracted much attention in recent years due to its good thermoelectric performance, low toxicity, and high elemental abundance. However, its relatively high thermal conductivity still restricts the further improvement in figure of merit (ZT). Here, we report a facile synthesis of CuAgSe/Cu₂Se composite ceramics to optimize the thermoelectric properties. Consequently, the thermal conductivity of the composite ceramics is greatly reduced due to the intrinsic low thermal conductivity of CuAgSe and the porous structures of the composites. Introducing a moderate amount CuAgSe can reduce the thermal conductivity to one-third of the value of pure Cu₂Se, while the corresponding power factor (PF) remains unchanged. Ultimately, the CuAgSe/Cu₂Se composite ceramics presented a good thermoelectric properties with a ZT value of 1.43 at 900 K. This work provides a simple and effective strategy to optimize Cu₂Se-based materials thermoelectric performance, which also are helpful to the optimization design of other thermoelectric systems.