Bismuth telluride (Bi
2
Te
3
) is a promising thermoelectric material for applications near room temperature. To increase the thermoelectric performance of this material, its dimensions and thermal transport should be decreased. Two-dimensional nanoplates with nanopores are an ideal structure because thermal transport is disrupted by nanopores. We prepared Bi
2
Te
3
nanoplates with single nanopores by a solvothermal synthesis and investigated their structural and crystallographic properties. The nanoplates synthesized at a lower reaction temperature (190 °C) developed single nanopores (approximately 20 nm in diameter), whereas the nanoplates synthesized at a higher reaction temperature (200 °C) did not have nanopores. A crystal growth mechanism is proposed based on the experimental observations.
High-purity hexagonal bismuth telluride (Bi 2 Te 3 ) nanoplates were prepared by a solvothermal synthesis method, followed by the fabrication of nanoplate thin films by the drop-casting technique. The Bi 2 Te 3 nanoplates exhibited a single-crystalline phase with a rhombohedral crystal structure. The nanoplates had a flat surface with edge sizes ranging from 500 to 2000 nm (average size of 1000 nm) and a thickness of less than 50 nm. The resulting Bi 2 Te 3 nanoplate thin films were composed of well-aligned hexagonal nanoplates along the surface direction with an approximate film thickness of 40 µm. To tightly connect the nanoplates together within the thin films, thermal annealing was performed at different temperatures. We found that the thermoelectric properties, especially the Seebeck coefficient, were very sensitive to the annealing temperature. Finally, the optimum annealing temperature was determined to be 250°C and the Seebeck coefficient and power factor were %300 µV/K and 3.5 µW/(cm&K 2 ), respectively.
To investigate the effect of adding single-wall carbon nanotubes (SWCNTs) to Bi 2 Te 3 nanoplate thin films, we prepared Bi 2 Te 3 nanoplate/SWCNTs nanocomposite thin films with different amounts of SWCNTs using a drop-casting technique. The Bi 2 Te 3 nanoplates prepared by solvothermal synthesis exhibited a single-crystalline phase with rhombohedral crystal structure. The nanoplates had flat surfaces with edge size of approximately 1 μm. The completed nanocomposite thin films were thermally annealed at 250 °C to improve their electrical conductivity. The electrical conductivity of the nanocomposite thin films with added SWCNTs improved, but the power factor decreased compared to those of the Bi 2 Te 3 nanoplate thin film. This occurred because the quality of Bi 2 Te 3 nanoplates in the nanocomposite thin films decreased due to excessive annealing as the introduced SWCNTs have high thermal conductivity. Therefore, we reduced the annealing temperature of nanocomposite thin films to 225 °C and found that the power factor was significantly improved.
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