Comparison of characteristics of Bi₂Te₃ and Bi₂Te_2.7Se_0.3 thermoelectric materials synthesized by hydrothermal process

In this research, a simple approach based on hydrothermal method was developed for the synthesis of high purity Bi₂Te_2.7Se_0.3 polyhedral nanoflakes and Bi₂Te₃ spherical nanoparticles. The synthesized Bi₂Te₃ and Bi₂Te_2.7Se_0.3 nanopowders were characterized by X-ray diffraction, Fourier transform infrared spectrometry, field emission electron microscopy, photoluminescence (PL) and ultraviolet–visible near-infrared spectroscopy. The results showed that the produced powders (Bi₂Te₃ and Bi₂Te_2.7Se_0.3) exhibit no chemical impurity formed during hydrothermal synthesis process. Besides, the ternary Bi₂Te_2.7Se_0.3 alloy showed less oxide bond versus the Bi₂Te₃ alloy. The results showed that Bi₂Te_2.7Se_0.3 powders possess a uniform nano-flake shape with an average size of 48 nm along with bandgap energy of 0.6 eV. Moreover, Bi₂Te₃ powders were characterized with a uniform spherical shape and an average size of 43 nm along with bandgap energy of 0.9 eV. The Bi₂Te_2.7Se_0.3 nanoplate powders exhibited a favorable bandgap and lower PL intensity due to the larger particle size compared with the spherical Bi₂Te₃ nanopowders. In conclusion, the obvious specifications of Bi₂Te₃-based materials were improved by the incorporation of selenium using a hydrothermal procedure. It is strongly believed that this synthesis approach and characterization methods will be important for the development of thermoelectric performance and applications of these groups of materials, such as sensors, laser diode, cooling system, fiber-optic systems.