Effect of ionic liquid amount (C8H15BrN2) on the morphology of Bi2Te3 nanoplates synthesized via a microwave-assisted heating approach

Bi2Te3 crystals with plate-like morphology have been successfully synthesized via a microwave-assisted heating approach in room temperature ionic liquid (RTIL) of 1-butyl-3-methylimidazolium bromide (C8H15BrN2). Scanning electronic microscopy (SEM) observation of as-synthesized Bi2Te3 confirmed their morphology of the hexagonal plates. It was observed that the edge and thickness values of as-synthesized Bi2Te3 were in the size of 0.5-2 mu m and less than 100 nm, respectively. High-resolution transmission electronic microscopy (HR-TEM) and selected area electron diffraction (SAED) results revealed that the Bi2Te3 plates are of single-crystal in nature with the growth direction of < 1 1 (2) over bar 0 >. In addition, as increasing the amount of ionic liquid, SEM results showed a novel evolution process of Bi2Te3 morphologies from mixture of Bi2Te3 nanorods and nanoplates to regular hexagonal plates, and then nanoplates with many small flecks. Furthermore, a possible mechanism regarding the formation of Bi2Te3 plates was proposed as well on the basis of the experimental results. The power factor of Bi2Te3 nanoplates is examined to evaluate its thermoelectric property. (C) 2011 Published by Elsevier B.V.