Thermoelectric properties of nanostructured bismuth telluride (Bi2Te3) with annealing time and its composite with reduced graphene oxide (RGO)

In the present work, thermoelectric performance of ethylenediaminetetraacetic acid assisted bismuth telluride (Bi2Te3), prepared by hydrothermal technique has been investigated. The samples after preparation are annealed in a vacuum chamber at 100 °C for 6 h and 10 h to compare its properties with the sample without annealing. The results show that the materials are nanocrystalline in nature, having rhombohedral lattice structure with a preferred orientation along (015) direction. Lattice parameters from Rietveld refinement show that ‘a’ decreases while ‘c’ increases with annealing time for Bi2Te3. Thermoelectric performance of the samples improve significantly with annealing time by one order of magnitude. These observations are in tune with the presence of antisite defects where Bi lattice sites are occupied by excess Te. Composites of Bi2Te3 with reduced graphene oxide (RGO) (1 and 3 wt%) (10 h) have been prepared and characterized to investigate thermoelectric performance. For Bi2Te3–RGO (1 wt%) composite, a maximum value of ZT (0.29), higher than Bi2Te3, at room temperature is obtained due to an increase in electrical conductivity of the composites.