Search

We report fabrication of nanostructured Bi2−xSbxTe3 using hydrothermal method followed by cold-pressing and evacuated-and-encapsulated sintering techniques. To obtain lower resistivity, the reaction temperature in the hydrothermal synthesis is investigated, and the effects on the ZT values of Bi2−xSbxTe3 are reported. Both the x = 1.52 and 1.55 samples hydrothermally synthesized at 160°C show lower resistivity than the x = 1.55 sample hydrothermally synthesized at 140°C. However, the power factor is lower for the samples synthesized at 160°C due to the accompanying smaller thermopower. All three samples exhibit remarkably low thermal conductivity of around 0.41 W m−1 K−1 at room temperature. The peak ZT value occurs at 270 K for all three samples, being ZT = 1.75, 1.29, and 1.17 for x = 1.55 (synthesized at 140°C), 1.55 (synthesized at 160°C), and 1.52 (synthesized at 160°C), respectively.

We report fabrication of compacted Bi0.5Sb1.5Te3 nanoplatelets using hydrothermal methods followed by cold pressing and sintering in an evacuated ampoule at various temperature of 300–380 °C. The compacted Bi0.5Sb1.5Te3 sintered at 340 °C has the highest power factor of 11.6 μW/cm·K2 and its thermal conductivity is 0.37 W/m·K at 295 K, which is very low as compared to the typical value of 1 W/m·K. The resulting dimensionless figure of merit ZT is 0.93 at 295 K.

High ZT values of nanostructured Bi2−xSbxTe3 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 = 1.55 exhibits a dimensionless figure of merit ZT = 1.65 at 290 K and 1.75 at 270 K with significant 60–70% improvement of that of the commercial state-of-the-art Bi2Te3 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.