High ZT values of nanostructured Bi 2Àx Sb x Te 3 for energy conversion are fabricated by hydrothermal methods followed by cold-pressing and sintering in an evacuated and encapsulated ampoule. We show that the sample with a nominal composition of x ¼ 1.55 exhibits a dimensionless figure of merit ZT ¼ 1.65 at 290 K and 1.75 at 270 K with significant 60-70% improvement of that of the commercial stateof-the-art Bi 2 Te 3 materials around room temperature. The significant ZT improvement arises from the much-reduced thermal conductivity. The low thermal conductivity is mainly due to the increased phonon scattering in the nanostructured materials.
Analysis of optical properties of porous silicon nanostructure single and gradient-porosity layers for optical applications J. Appl. Phys. 112, 053506 (2012) Holographic modification of TiO2 nanostructure for enhanced charge transport in dye-sensitized solar cell J. Appl. Phys. 112, 043110 (2012) Universal ultrafast sandpaper assisting rubbing method for room temperature fabrication of two-dimensional nanosheets directly on flexible polymer substrate Appl. Phys. Lett. 101, 073113 (2012) Local structure, paramagnetic properties, and porosity of natural coals: Spectroscopic studies Abstract. Nanoplatelets of Bi 2-x Sb x Te 3 with nominal composition of x = 1.5 are synthesized using hydrothermal methods. The resulting powders are cold pressed and sintered in an evacuated and encapsulated ampoule at 340°C. Scanning electron microscope atomic force microscope, and transmission electron microscope are used to observe the microstructure of nanoplatelets and consolidated Bi 0.5 Sb 1.5 Te 3 . The consolidated Bi 0.5 Sb 1.5 Te 3 is in fact nanostructured bulk. The power factor and thermal conductivity are 11.6 μW/cm-K 2 and 0.37 W/m K at 295 K, respectively. The small thermal conductivity could be largely attributed to its nanostructured nature of the consolidated bulk. The resulting dimensionless figure of merit ZT is 0.93 at 295 K.
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