Bismuth Telluride (Bi2Te3) nanocrystallites: Studies on growth morphology and its influence on the thermoelectric properties

Abstract

Growth of Bismuth Telluride (Bi2Te3) nanocrystallites by solvothermal method resulted in an incomplete hexagonal flake-like (BTFL) structure for surfactant-free growth and complete hexagonal morphologies (BTHP) for the PVP surfactant mixed growth respectively identified through FESEM studies. XRD characterization revealed the crystallization of pure phase of Bi2Te3 at 210 °C for PVP-free growth and at 200 °C for PVP-assisted growth. Raman studies shows a noticeable difference in the appearance of peak positions for hexagonal nanoplatelets. Laser flash measurement of total thermal conductivity (κtot) resulted in the lowest value of 0.39 Wm−1K−1 for the BTFL pellet and 0.44 Wm−1K−1 for BTHP. Estimated lattice thermal conductivity resulted in 0.16 Wm−1K−1 for BTFL pellet and 0.25 Wm−1K−1 for the BTHP pellet. Temperature-dependent electrical conductivity studies reveal semiconductor behaviour for BTFL pellet and semi-metallic behaviour for BTHP pellet. Calculation of figure of merit (ZT) based on the measured values exhibits ZT value of 0.76 for BTFL and 0.64 for BTHP pellet. Details are presented in this paper.