Toward controlled thermoelectric properties of Pb and Sb co-doped nanostructured Thallium Telluride for energy applications

Abstract

Here, the structure-dependent electronic, thermal, and transport properties of nanostructured thallium telluride (Tl8PbxSb2−xTe6) through controlled variation in Pb and Sb (x = 1.96, 1.97, 1.98, 1.99) concentrations have been investigated. In the temperature and concentration-dependent electrical conductivity measurements, the highest electrical conductivity 131.96 × 103 W-1m-1 at 300 K was measured for x = 1.99 and the maximum observed Seebeck value for the optimized Tl8Pb1.96Sb0.04Te6 nanoparticles was 110.7 μV/K at 550 K. Such an increased value of the Seebeck coefficient led to the achievement of a significantly improved high-power factor, which was found to be increasing with temperature and decreasing with the increase of Pb concentration. The density functional theory calculations performed for Pb and Sb co-doped Tl5Te3 resulted in the enhanced σe and S with a significant reduction in electronic thermal conductivity (κe) and is found consistent with experimentally measured κe. The highest ZT = 0.35 and 0.18 were recorded experimentally and theoretically for Pb and Sb co-doped in Tl5Te3 nanoparticles.