Competing Grain Growth Pathways in Anisotropic Bi₂Te₃-Based Thermoelectric Nanoplates

Area of Science:

• Materials Science
• Nanotechnology
• Condensed Matter Physics

Background:

• Thermoelectric nanoplates from van der Waals (vdW) materials like Bi2Te3 are crucial for flexible electronics.
• Grain boundary (GB) microstructure critically impacts their performance.
• Atomic-scale mechanisms of grain growth in anisotropic vdW materials are not well understood.

Purpose of the Study:

• To investigate the competing atomic-scale mechanisms of grain growth in Bi2Te3 (BT) and Sb-doped Bi2Te3 (BST) nanoplates.
• To understand how Sb doping influences grain boundary evolution and nanoplate morphology.
• To provide insights for designing advanced thermoelectric materials.

Main Methods:

• In situ scanning transmission electron microscopy (STEM) for real-time observation.
• Density functional theory (DFT) for electronic structure calculations.
• Molecular dynamics (MD) simulations for atomic-level behavior.

Main Results:

• Undoped BT nanoplates exhibit preferential atomic reshaping, migrating atoms to stabilize facets.
• Sb doping in BST nanoplates introduces Sb-Te interfacial phases.
• Sb-Te phases promote grain boundary coalescence, shifting the dominant growth pathway to collective merging.

Conclusions:

• Chemical modification, specifically Sb doping, can steer grain boundary evolution in vdW nanoplates.
• The dominant grain growth mechanism (reshaping vs. merging) can be controlled.
• This understanding is vital for optimizing anisotropic layered materials for thermoelectric applications.