Interface Potential Induced High Thermoelectric Performance of the Heterostructured Ca ₃ Co ₄ O ₉ /AgNWs Composites Ceramics

Nano‐inclusions are crucial for hole carrier transport in high‐performance thermoelectric materials. However, nanoparticles often exhibit limited effectiveness due to energy barriers that impede phonon scattering, resulting in undesirably high lattice thermal conductivity. In contrast, nanowires provide directional carrier transport channels while leveraging size effects to effectively suppress lattice thermal conductivity. Herein, the silver nanowires (AgNWs) were introduced into the (Ca 0.87 Ag 0.1 La 0.03 ) 3 Co 4 O 9 matrix, and the Ag bundles were formed. The (Ca 0.87 Ag 0.1 La 0.03 ) 3 Co 4 O 9 /AgNWs composites ceramics were prepared by the spark plasma sintering process, and the interface potential regulation was used to successfully synergistically optimize electrical and thermal parameters. The ρ values of all samples significantly decreased in the entire temperature range and varied from 89.2 mΩ·cm at 323 K to 15.4 mΩ·cm at 1073 K. The peak Seebeck coefficient of 195.3 µV/K was obtained, and the total thermal conductivity reached 0.99 W/(m·K). As a result, a maximum ZT value of 0.25 at 1073 K. By introducing AgNWs and forming the Ag bundles as the additional phonon scattering sources, the lattice thermal conductivity of the composite ceramics was reduced. The present work undoubtedly elucidates a new strategy for offering a comprehensive understanding of the role of the heterojunction interface and interface potential in improving thermoelectric performance.