Enhanced performance of thermoelectric nanocomposites based on Cu12Sb4S13 tetrahedrite

Fine-grained and nanostructured composites have long been known for their superiority in enhancing thermoelectric performance; however, exploring these structures based on Cu12Sb4S13 tetrahedrites is difficult due to the methods of synthesis. This study reports Nb2O5 nanoparticles-dispersed Cu11.5Ni0.5Sb4S13-δ composites synthesized by a facile method combining mechanical alloying (MA) and spark plasma sintering (SPS). The enhanced electrical conductivity and the high power factor were obtained over the entire temperature ranges, likely derived from the fine-grained nanostructures through the repeated MA and SPS process. The uniformly distributed Nb2O5 nanoparticles and nanopores indicate the effectiveness of reducing the lattice thermal conductivity, below 0.6 W m−1 K−1, due to strong low-mid frequency phonon scattering. A small quantity of Nb2O5 addition (0.3 vol%) led to a high ZT ~1.2 at 723 K, which increased by ~50% compared to the matrix sample. These nanocomposites also possessed high average ZT, thermoelectric conversion efficiency, and fracture toughness.