Synthesis, Evolution of Morphology, Transport Properties for Bi₂Te₃ Nanoplates

Bi₂Te₃ has an extensive application as thermoelectric materials. Here, large scale Bi₂Te₃ single-crystal hexagonal nanoplates(NPs) with size of 0.4–0.8 μm were synthesized successfully by hydro-thermal method. X-ray diffraction (XRD), scanning electron microscope (SEM), and transmission electron microscope (TEM) were used to characterize the Bi₂Te₃ nanoplates, which confirm the single crystal quality and smooth surface morphology with large size. We discussed the morphology-evolution in detail the influence of various reaction factors which including: the reaction temperature, the reaction time, the surfactants of the polyvinyl pyrrolidone (PVP) and pH value. The synthesis method is not only green, but also shortens the reaction time and improves the reaction efficiency. The Bi₂Te₃ nanopowders were hot-pressed into solid state pellets through spark plasma sintering (SPS). The values of the electrical conductivity <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mi>σ</mi></semantics></math></inline-formula> were about 0.16 × 10⁻⁵ Sm⁻¹ and 0.22 × 10⁻⁵ Sm⁻¹ at room temperature and 530 K, respectively. The values of the Seebeck coefficient S were around −81 μVK⁻¹ and −118 μVK⁻¹ at room temperature and 530 K, respectively.