Preparation of Te nanopowder by vacuum distillation

Nanosize thermoelectric powder can exhibit improved performance index owing to reduction of lattice thermal conductivity. Currently, chemical or physical processes such as polyol synthesis, gas atomization, and mechanical milling are employed to prepare such powders. In this study, Te nanopowders of 5N purity were prepared using an evaporation–condensation process. The formation mechanisms for Te nanopowders and coarse crystals are discussed and correlated with condensation temperature gradient and Ar flow rate. Prepared Te powders exhibited particle sizes ranging from tens to hundreds of micrometers upon high-temperature processing to as low as tens of nanometers at low-temperature processing (room temperature). In addition, these nanopowders began to oxidize at 225 °C, and subsequently, began to evaporate at 733 °C, as observed through thermogravimetric analysis. The procedure presented here has been found to be an economical method for preparing high-purity Te nanopowders from low-purity Te feedstock.