Surfactant-Induced Structural Phase Transitions and Enhanced Room Temperature Thermoelectric Performance in n-Type Bi₂Te₃ Nanostructures Synthesized via Chemical Route

A systematic study of surfactant-assisted aqueous-based low-temperature chemical method for the synthesis of different phases of Bi–Te-based nanostructures with different morphologies ranging from nanocrystals to nanorods/nanosheets is investigated. The n-type Bi2Te3 nanostructures are inherited from the low-temperature reflux reaction, and a structural phase transition is established for different surfactant concentrations and reaction time. Simultaneous optimization of reaction time and surfactant concentration yields the formation of hexagonal Bi2Te3 nanocrystals even with lower reaction time, which is the desirable crystal structure for obtaining enhanced thermoelectric properties. Tuning the surfactant concentration from 50 to 100 mmol facilitates the formation of low-dimensional structures of Bi2Te3, which is evident from the refined X-ray diffraction results and high-resolution transmission electron microscopy analysis. Bi2Te3 nanostructures inherited from 24 h reaction time with 100 mmol surfactant concentration exhibit a promising figure of merit of 0.75 at 300 K. An in-depth understanding of the reaction mechanism to form BT nanostructures is explained. The present study provides an efficient and simple method to develop low dimensional nanostructures for improved thermoelectric performance.