Investigating Phase Transition and Morphology of Bi-Te Thermoelectric System

Abstract

The optimization of secondary of secondary phase in a thermoelectric materials can help to improve the efficiency of the material. Being a potential candidate, Bismuth telluride (Bi 2 Te 3 ) nanoparticles were synthesized via different routes and profiles to optimize its pure single phase.Systematic characterizations were performed with the help of X-ray diffraction, Rietveld refinement, Field effect-Scanning electron microscopy(FE-SEM) for structural and morphological behavior. Rietveld refinement in XRD-data of the samples revealed that only a small amount (∼ 1.6%) of Bi 2 Te 3 was formed in co-precipitation method, while hydrothermal technique increases this phase with increment in synthesis duration. This work focussed on the phase evolution of Bi 2 Te 3 with increasing synthesis duration time at constant temperature. XRD Rietveld refinement revealed that 84% pure phase was obtained when sample is synthesized at 150 • C for 48 hours by hydrothermal technique. FE-SEM and Energy Dispersive X-ray (EDX) analysis also indicated that impure phase is decreased along with atomic percentage of oxygen from 37% to 11% in hydrothermally synthesized sample. The detailed analysis has generalized the growth mechanism in Bi 2 Te 3 phase evolution by the diffusion of Bi into Te nanorods to fabricate hexagonal Bi 2 Te 3 .