Achieving enhanced thermoelectric performance in chemically fluctuating AgCuTe-based material

AgCuTe has attracted significant interest due to their superior electrical and thermal transport characteristics. In this work, we focuses on investigating the effects of Se and S solid solution on AgCuTe thermoelectric properties. A series of AgCu(Te, Se, S) solid solutions were synthesized via melting reaction. We found these compositions effectively inhibited the typical hexagonal-to-cubic phase transition and showed features of secondary phase segregation, such as Ag${}_2$Te, Cu${}_2$Te, and Cu${}_2$S. These nano- to microscale chemistry fluctuations significantly affect the thermoelectric transport properties, particularly thermal transport, resulting in an exceptional low lattice thermal conductivity of 0.19 W m⁻¹ K⁻¹, which was approaching the amorphous limits. Consequently, a maximum figure of merit zT up to 1.4 was obtained at 723 K for AgCuTe_0.65Se_0.1S_0.25 sample. This work investigates the relationships between composition, structure, and thermoelectric properties of AgCuTe, providing substantial support for the further development of high-performance AgCuTe-based materials.