ICT2014 Abstracts

Bi_0.5Sb_1.5Te₃ nano-composites prepared through hot pressing. Bi_0.5Sb_1.5Te₃ nano-composites were fabricated by mixsure of melt-spun nano-grain Bi_0.5Sb_1.5Te₃ and micro grain zone melting Bi_0.5Sb_1.5Te₃.  An annealing process was performed following by hot pressing process. Before annealing process, Seebeck coefficient is ~ 220 mV/K and ZT_max~1.2@400K for 40wt% nano-phase Bi_0.5Sb_1.5Te₃ nano-composite. After annealing process, the Seebeck coefficient increased from 220 to 243 mV/K. However, electrical and thermal conductivities are similar. Consequently, the ZT was enhanced from 1.2 to 1.42 with embedding Te nano-precipitations in Bi_0.5Sb_1.5Te₃.  SEM data shows there were aggregated Te precipitations inside the annealing sample, where grain size of Te precipitations are ~10-30 nm. The amount of aggregated Te precipitations is ~ 5.1 vol%. According to the theoretical and experimental studies in BiTe and PbTe compound, semiconductor with metal nano-inclusion will introduce carrier energy filtering effect, which will enhance Seebeck coefficient. We speculate that the aggregated Te nano-precipitations would introduce carrier energy filtering effect in Bi_0.5Sb_1.5Te₃ causing the improvement only on Seebeck coefficient.