Microstructural behavior of the heat treated n-type 95% Bi2Te3–5% Bi2Se3 gas atomized thermoelectric powders

In this research, n-type 95% Bi2Te3–5% Bi2Se3 doped with 0.04% SbI3 thermoelectric powders were manufactured by gas atomization process and subsequently, the effects of rapid solidification and heat treatment on the microstructure of the powder particles were investigated. The crystal structures were analyzed by X-ray diffraction (XRD) and cross-sectional microstructures were observed by the scanning electron microscopy (SEM). The rapidly solidified powders consist of homogeneously distributed needle shape intermetallic compounds. However, the size of the intermetallic compounds increased with the increasing powder size, whereas the oxygen content in the produced powder decreased. Heat treatment of the powders for various temperatures and periods showed a significant increase in the grain size resulting in a reduction in hardness. In addition, with the increasing heat treatment temperatures and periods, the orientation factor of the powder particles decreased, which is also evident in case of the reduction treated powders.

Research highlights▶ The effect of high temperature on the microstructure of the 95% Bi2Te3–5% Bi2Se3 powder was studied. ▶ Powders heat treated at different conditions showed microstructural coarsening resulting in a reduction in hardness. ▶ The orientation factor was not much affected by the heat treatment and reduction treatment of the powders.