(Bi,Sb)2Te3/SiC nanocomposites with enhanced thermoelectric performance: Effect of SiC nanoparticle size and compositional modulation

Abstract

Fabrication of nanoparticle-dispersed composites is an effective strategy for enhancing the performance of thermoelectric materials, and in particular SiC nanoparticles have been often used to create composites with Bi2Te3-based applied thermoelectric materials. However, the effect of particle size on the thermoelectric performance is unclear. This work systematically investigated the electrical and thermal properties of a series of (Bi,Sb)2Te3-based nanocomposites containing dispersed SiC nanoparticles of different sizes. It was found that particle size has a significant impact on the electrical properties with smaller SiC nanoparticles giving rise to higher electrical conductivity. Even though the dispersed SiC nanoparticles enhanced the Seebeck coefficient, no apparent dependence of the enhancement on the particle size was observed. It was also found that smaller SiC nanoparticles scatter phonons to some extent while the larger nanoparticles contribute to increased thermal conductivity. Eventually, the highest ZT value of 1.12 was obtained in 30 nm-SiC dispersed sample, corresponding to an increase by 18% from 0.95 for the matrix made from commercial scraps, and then the ZT was further boosted to 1.33 by optimizing the matrix composition and expelling excess Te during the optimized spark plasma sintering process. This work proves that the dispersion of smaller SiC nanoparticles in p-type (Bi,Sb)2Te3 materials is more effective than the dispersion of larger nanoparticles. In addition, it is revealed that additional compositional and/or processing optimization is vital and effective for obtaining further performance enhancement for nanocomposites of SiC nanoparticles dispersed in (Bi,Sb)2Te3.