Potential Applications In Thermoelectric Devices Research Articles

Electrical transport properties of microwave-synthesized Bi2Se3−xTex nanosheet

Tellurium (Te) doped bismuth selenide (Bi2Se3−xTex) nanosheets have been successfully synthesized by the microwave-assisted method in the presence of ethylene glycol (EG). The obtained products were characterized by powder X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), selected-area electron diffraction (SAED), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy techniques. The electrical transport properties of the nanosheets are investigated by measuring the electrical conductivity and the Seebeck coefficient at temperatures ranging from 298 to 523 K. The power factor values of the Bi2Se3−xTex nanosheet vary with different doping concentrations of Te, and the maximum power factor can reach 178 μW m−1 K−2 at 523 K for Bi2Se2.7Te0.3, indicating the potential application in thermoelectric devices.

Molecular dynamics simulation for heat transport in thin diamond nanowires

The phonon thermal conductivity in diamond nanowires (DNW) is studied by molecular dynamics simulation. It is found that the thermal conductivity in narrower DNW is lower and does not show obvious temperature dependence; a very small value (about 2.0 W/m/K) of thermal conductivity is observed in ultra-narrow DNW, which may be of potential applications in thermoelectric devices. These two phenomena are probably due to the dominant surface effect and phonon confinement effect in narrow DNW. Our simulation reveals a high anisotropy in the heat transport of DNW. Specifically, the thermal conductivity in DNW along [110] growth direction is about five times larger than that of [100] and [111] growth directions. The anisotropy is believed to root in the anisotropic group velocity for acoustic phonon modes in DNW along three different growth directions.

Raman scattering investigation of Bi 2Te 3 hexagonal nanoplates prepared by a solvothermal process in the absence of NaOH

Hexagonal Bi 2Te 3 nanoplates were synthesized by a simple solvothermal process in the absence of NaOH. The composition, morphology and size of the as-prepared products were characterized by powder X-ray diffraction (XRD) and transmission electron microscopy (TEM). Raman scattering optical properties of the as-prepared Bi 2Te 3 nanoplates were investigated by micro-Raman spectroscopy. The Raman spectrum shows that infrared (IR) active mode (A 1u), which must be odd parity and is Raman forbidden for bulk crystal due to its inversion symmetry, is greatly activated and shown up clearly in Raman scattering spectrum. We attribute the appearance of infrared active (A 1u) in Raman spectrum to crystal symmetry breaking of Bi 2Te 3 hexagonal nanoplates. The as-grown Bi 2Te 3 hexagonal nanoplates, exhibiting novel Raman optical properties compared with bulk crystals, may find potential applications in thermoelectric devices.