Nanostructure Engineering and Performance Enhancement in Fe₂O₃-Dispersed Cu₁₂Sb₄S₁₃ Thermoelectric Composites with Earth-Abundant Elements

Nanostructuring and defect engineering are increasingly employed as processing strategies for thermoelectric performance enhancement, and special attention has been paid to nanostructured interfaces and dislocations that can effectively scatter low- and mid-frequency phonons. This work demonstrated that their combination was realized in Fe₂O₃-dispersed tetrahedrite (Cu₁₂Sb₄S₁₃) nanocomposites, leading to significantly reduced thermal conductivities around 0.9 W m^-1 K^-1 at all temperatures and hence a high ZT value of ∼1.0, which increases by ∼33% compared with that of the matrix. The plausible enhancement mechanisms have been analyzed with an emphasis on the incorporation of magnetic γ-Fe₂O₃ nanoparticles (NPs) into Cu_11.5Ni_0.5Sb₄S₁₃, leading to various nanostructures (NPs, nanoprecipitates, and nanotwins) and dislocations. A calculated efficiency of ∼9.3% and an average ZT of 0.63 also reveal the potential application of tetrahedrite at medium temperatures. Additionally, the mechanical properties are improved because of a second phase strengthening and nanotwin structures.