Preparation and thermoelectric properties of inhomogeneous bismuth telluride alloyed nanorods

Abstract

We herein report a large-scale hydrothermal synthesis of bismuth telluride nanorods. The effects of different additives, e.g. EDTA ligand, NH4Cl, SDBS and hydrazine hydrate, on the morphology of final product have been systematically investigated. The dimensional sizes of the resultant bismuth telluride alloyed (BTA) nanorods were around 500nm in length and 20nm in diameter. Different analytical methods were utilized to determine the chemical composition of the BTA nanorods. HRTEM observation revealed that the nanorods are not homogeneous in terms of composition along the c axis of each nanorod. The formation of such 1D nanorods was proposed to be closely related to the lattice stress caused by the spiral chain along the c axis of trigonal Te during the transition from one dimensional nanowires of Te template to BTA nanorods. To measure the thermoelectric properties of our products, the BTA nanorods were consolidated into bulk pellets by both spark plasma sintering (SPS) or high pressure and high temperature (HPHT) sintering. The corresponding maximal figure of merits (ZT values) for the pellets made by SPS and HPHT are 0.42 and 0.47 at 430K, respectively.