Effects of Ni and carbon-coated Ni addition on the thermoelectric properties of 25Bi2Te3+75Sb2Te3 base composites

In this paper, we report the effect of nickel (Ni) and carbon coated nickel (C-Ni) on the thermoelectric and mechanical properties of 25Bi(2)Te(3)+75Sb(2)Te(3) (GA) base composites. Ni and C-Ni powders were synthesized using pulse wire evaporation and mixed with 25Bi(2)Te(3)+75Sb(2)Te(3) in a planetary ball mill. The morphology of the Ni and C-Ni powders and GA + x (x = none, Ni, or C-Ni) composites were examined using transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The thermoelectric properties of the GA + x (x = none, Ni, or C-Ni) composites shows that the addition of Ni increases the carrier concentration while the presence of C-Ni reduces the carrier concentration to a level comparable to the bare sample (x = 0). Subsequently, the Seebeck coefficient of the GA + C-Ni sample increases by about 18% more than in the bare sample. The thermal conductivity of the GA + Ni and GA + C-Ni samples was considerably lower at room temperature compared to the bare sample. The mechanical properties of the GA + Ni and GA + C-Ni composite samples show a three-fold improvement compared to the bare sample. (C) 2017 Elsevier B.V. All rights reserved.