Room temperature Bi2Te3-based thermoelectric materials with high performance

Several off-stoichiometric compositions Bi0.5Sb1.5+xTe3+δ (x = 0.2; δ = 0, 0.12, 0.14) were deliberately synthesized to produce in-situ composites based on compositional engineering approach. The structural characterization of these materials employing XRD, SEM, and HR-TEM reveals the formation of in-situ-composites containing Bi0.5Sb1.5Te3 as matrix phase and minor phases of either Sb rich or Te rich in different compositions. Thermoelectric properties of these Bi0.5Sb1.5+xTe3+δ (x = 0.2; δ = 0, 0.12, 0.14) composites were studied in a wide range of temperatures extending from room temperature to 500 K. The electronic transport of these composites exhibits p-type semiconducting materials. The lowest thermal conductivity of ~ 0.69 W/m K @310 K was observed for Bi0.5Sb1.7Te3.12 composite, which was noted to be 14% reduced thermal conductivity when compared with that of the state-of-the-art Bi0.5Sb1.5Te3 (κ=\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$=$$\end{document} 0.82 W/m K) material. In addition to this, an enhanced power factor was also observed in Bi0.5Sb1.7Te3.12 which is primarily due to increased electrical conductivity of these materials. This enhanced power factor of the composition of Bi0.5Sb1.7Te3.12 coupled with reduced thermal conductivity yields to high ZT ~ 1.13 at nearly room temperature, making these materials viable for large scale applications.