ICT2014 Abstracts

Bismuth telluride based alloys are among state-of-the-art thermoelectric materials with high figure-of-merit and have been scaled up for commercial application, of which zone melting (ZM) has long been proved to be the most effective and promising method for mass production. However, the inferior mechanical properties and machinability of ZM ingots are detrimental for the long-term use and reliability in application. Melt spinning combined with rapid sintering has generally been regarded as a fast and novel technique to introduce multiscale nanostructures to enhance thermoelectric performance. Accordingly, in the current study, melt spinning and plasma activated sintering (MS-PAS) were employed to fabricate p-type Bi_0.5Sb_1.5Te₃ alloys, aiming at improving machinability and mechanical properties. Young’s modulus, Vickers hardness, fracture toughness, and temperature dependent flexural strength and compressive strength were investigated as a function of MS linear speed and grain size. Specimens prepared by MS-PAS exhibit over 200 % increase of compressive strength and 20-30% increase of flexural strength at room temperature in comparison with ZM samples cut along ZM direction. Moreover, the Vickers hardness of MS-PAS samples shows ~50-70%  increase over ZM ingots, indicating more superior machinability. The enhancement of these mechanical properties can be mainly attributed to remarkable reduction in grain size and also abundant nanostructures at grain boundaries induced by MS-PAS technique.