THE EFFECT OF SINGLE WALLED CARBON NANOTUBES ON THE THERMOELECTRIC PROPERTIES OF BISMUTH TELLURIDE

Abstract

Modern new technologies, including carbon nanomaterials, polymers performed electronically, and their nanocomposites enhance the performance of thermoelectric materials. Thermoelectrical responses can be improved by simultaneously tuning different properties within the material, such as nano structuring, nanocomposites, and doping. The purpose of this work is to determine the effect of single walled carbon nanotubes (SWCNT) on the thermoelectric properties of an n-type bismuth telluride alloy. Mechanical alloying and compaction sintering techniques are used to prepare SWCNT/Bi2Te2.55Se0.45 composites. Experiments are conducted with different concentrations (0.01, 0.025, 0.1 and 0.5 weight percent) and duration times of 20 hours. The results of the thermoelectric characteristics of SWCNT indicates that ball milling technique influences both its structure and agglomeration. The CNT filler is added during the step of mechanical milling, as this preserves SWCNT structure and increases its electrical conductivity. Additionally, it is demonstrated that SWCNT milling technique improves the Seebeck coefficient. While an increase in thermal conductivity is expected as a result of the high electrical conductivity due to increased scattering at the new interfaces, a significant drop in the lattice thermal conductivity is attained. The figure-of-merit for the optimal sample with 0.1 percent SWCNT added in 20 milling hours has improved by 13% at room temperature indicating a value of 0.3, and by 32% at 156.9°C indicating the highest ZT value of 0.6.