Synthesis And Properties Of Bi₂Se₃ Thermoelectric Nanostructures

Thermoelectric materials are also named temperature battery materials, which can convert electric energy directly to thermal energy and vice versa. It is a novel functional material which can be used in refrigeration and power generation. Bismuth selenide is not only an important Ⅴ-Ⅵ compound with a narrow band gap of 0.3eV but also a promising thermoelectric material. It has the high value of research.In the thesis, one-dimensional bismuth selenide nanowires were synthesized in a horizontal furnace via catalyst-free chemical vapor deposition using high-pure bismuth selenide powder, graphite paper and argon as source material, substrate and carrier gas, respectively. The morphologies and structures of obtained products were characterized by scanning electron microscopy(SEM), transmission electron microscopy(TEM), high-resolution transmission electron microscopy(HRTEM), selected area electron diffraction(SAED) and energy disperse X-ray spectroscopy(EDX). The results indicated that the samples were one-dimensional bismuth selenide nanowires with smooth surface and high quality crystallinity, which belonged to rhombohedral phase with space group R-3m. According to the growth characteristic and the relevant literature, we discussed the growth mechanism of the obtained bismuth selenide nanowires. The method is very novel and has not been reported, which provides a new method for synthesizing one dimensional nanostructures of other layered-like materials.Bismuth selenide nanosheets were fabricated by solvothermal technique using Bi(NO3)3 ·5H2O, SeO2, N,N-Dimethylformamide(DMF), Oleic acid(OA) and polyvinyl pyrrolidone(PVP). The phase, morphologies and structures of obtained products were characterized by XRD, SEM, TEM, HRTEM and SAED. The results showed that the products were bismuth selenide nanosheets with rhombohedral phase and high quality crystallinity, whose lateral dimension and thickness could reach to 6μm and 30 nm, respectively.We discussed the effects of the dosage of PVP on the products. The result indicates that the dosage of PVP affects not only the thikness but also the size of the bismuth selenide nanoplates. Due to the anisotropic properties of bismuth selenide nanoplates, we can integrate other electronic devices on the biemuth selenide nanoplates, and develop new devices with novel properties.