Decoding Thermal Stability: <i>In Situ</i> Insights into Phase Controlled Phosphine-Free Colloidal Bi-Te Nanosheets.
basic_science · Level V
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- Record sourced from PubMed, PMID 42435342.
- Also identified by DOI 10.1021/acsnano.6c07572.
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Abstract
Bismuth telluride (Bi<sub>2</sub>Te<sub>3</sub>) is a prototypical V-VI semiconductor of interest for both thermoelectric and topological applications; however, phase-selective synthesis and thermal stability across the bismuth-telluride homologous series remain poorly understood. We report a facile and phosphine-free colloidal synthesis approach for a phase-selective synthesis of Bi<sub>2</sub>Te<sub>3</sub>, BiTe, and Bi<sub>4</sub>Te<sub>5</sub> nanosheets with well-defined hexagonal morphology. By controlling precursor chemistry and reaction temperature, we achieved the selective formation of different phases within the (Bi<sub>2</sub>)<sub><i>m</i></sub>(Bi<sub>2</sub>Te<sub>3</sub>)<sub><i>n</i></sub> homologous series. Based on <i>in situ</i> heating studies, BiTe and Bi<sub>4</sub>Te<sub>5</sub> nanosheets transform into Bi<sub>2</sub>Te<sub>3</sub> at ∼340 °C, followed by preferential Te sublimation under vacuum or oxidation in air at higher temperatures. We discuss plausible mechanisms for these phase transformations. EDS analysis and FFT analysis of STEM images provide direct evidence for the temperature-dependent compositional and structural changes and highlight the close thermal relationship among these phases. These results not only advance fundamental understanding of phase stability and thermal behavior in bismuth-tellurides at the nanoscale but also establish a framework for understanding structural evolution in related homologous series, providing insights into their potential future applications in thermoelectric, spintronic, and topological systems.