Solvothermally optimizing AgTe/AgS composites with high thermoelectric performance and plasticity.

Silver-based fast ionic conductors show promising potential in thermoelectric applications. Among these, AgS offers unique high plasticity but low electrical conductivity, whereas AgTe exhibits high intrinsic electrical conductivity yet faces limitations due to high thermal conductivity and poor plasticity. Developing a composite thermoelectric material that combines the benefits of both is therefore essential. Here, this study reports the successful synthesis of AgTe/AgS composites a facile and low-cost solvothermal method. By finely adjusting the composition of AgS and AgTe to obtain the optimized carrier concentration and the enhanced mobility, the figure of merit of AgTe/AgS composites reached ∼0.42 at 373 K and ∼0.38 at 298 K, both surpassing those of pure AgS and AgTe. This increase in also benefits from lattice defects created by the solvothermally synthesized biphasic composition, effectively scattering phonons of various wavelengths and reducing thermal conductivity compared to pure AgTe. Additionally, the plasticity of the AgTe/AgS composites improved considerably over pure AgTe, achieving a bending strain of ∼2.5% ( ∼1.2% for intrinsic AgTe). This study can fill a critical gap in the research on composite silver-based fast ionic conductors synthesized wet chemical methods and provide valuable guidance for future exploration.