Effects of Nanoparticle Size on the Thermoelectric and Mechanical Properties of Skutterudite Nanocomposites

Nano-Co4Sb11.5Te0.5/Co4Sb11.5Te0.5 composites with different nanoparticle sizes and contents were obtained by ultrasonic dispersion followed by ball-milling and spark plasma sintering (SPS) processes. It was found that the nanoparticles obviously grew in size after SPS; most of them were larger than 200 nm in the 5%50 h and 10%50 h samples, while they were 100 nm to 200 nm in the 3%100 h and 5%100 h samples. The thermoelectric (TE) and mechanical properties of the nanocomposites with different sizes and contents were then characterized. Our results show that the TE properties were not noticeably affected, while the flexural strength and fracture toughness increased remarkably with the nanoparticle content, and the nanoparticle size had a notable effect on the mechanical properties of the nanocomposites; that is, the smaller the nanoparticles, the greater their reinforcing and toughening effects.