Enhancement in thermoelectric performance of hydrothermally synthesized Ca and Sb co-doped Bi₂Te₃ nanostructures

Abstract

Ca & Sb co-doped Bi2Te3 compounds have been prepared by hydrothermal method at 210 ℃ for 24 hr and investigated their thermoelectric properties. Phase purity and crystallinity were analyzed by XRD. All the prepared samples have rhombohedral crystal structure with space group R-3m. The hexagonal nanoplate-like morphology was examined by FESEM. Elemental analysis was done with EDX. Band gap energy of prepared samples has values in the range of ~0.40-0.65 eV, obtained by Tauc plot. The Raman shift was obtained at a lower frequency with doping. Carrier concentration increased with doping from 3.18×1020 cm-1 to 9.34×1020 cm-1. The high value of power factor (PF) of ~10.8 ×10-4 Wm-1K-2 was obtained due to high carrier concentration. An ultralow lattice thermal conductivity of ~0.28 and ~0.63 W/mK at 420 K, was obtained for Ca0.06Bi1.88Sb0.06Te3 and pure Bi2Te3, respectively. A maximum ZT of ~0.78 at 386 K was obtained for Ca0.03Bi1.94Sb0.03Te3. The value of ZT thus obtained is about ~ 51% higher than the ZT of pure Bi2Te3 (~0.39 at 386 K).