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

Abstract − Ca & Sb co-doped Bi 2 Te 3 compounds have been prepared by hydrothermal method at 210 °C for 24 h 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 × 10 20 cm −1 to 9.34 × 10 20 cm −1 . The high value of power factor (PF) of ∼10.8 × 10 –4 Wm −1 K −2 was obtained due to high carrier concentration. An ultralow lattice thermal conductivity of ∼0.28 and ∼0.63 W mK −1 at 420 K, was obtained for Ca 0.06 Bi 1.88 Sb 0.06 Te 3 and pure Bi 2 Te 3 , respectively. A maximum ZT of ∼0.78 at 386 K was obtained for Ca 0.03 Bi 1.94 Sb 0.03 Te 3 . The value of ZT thus obtained is about ∼ 51% higher than the ZT of pure Bi 2 Te 3 (∼0.39 at 386 K).