Tailoring bismuth telluride nanostructures using a scalable sintering process and their thermoelectric properties

Abstract

Bismuth telluride (Bi₂Te₃) nanocrystals were synthesized using a wet chemical method, and 1 mm thick pellets of nanocrystals with a 10 mm diameter were made using a high pressure and high temperature sintering (HPHTS) process. The nanostructures were tailored using the sintering process, and the impact of the sintering temperature on the morphological evolution and phase transformation of the pelletized Bi₂Te₃ nanocrystals were studied using standard analytical techniques. A phase change from Bi₂Te₃ to BiTe was observed in pellets sintered at high temperatures, and the BiTe phase dominated in the pellets sintered at 773 K. The thermoelectric properties of the as-prepared and sintered pellets were measured. The Seebeck coefficient of the Bi₂Te₃ nanocrystals increased with sintering temperature, and decreased at higher sintering temperatures (>673 K). Moreover, the power factor of the Bi₂Te₃ nanocrystals was significantly enhanced by sintering. The variations in the Seebeck coefficient and power factor are explained with a proposed model using the phase and morphological changes in the sintered Bi₂Te₃ pellets.