Insight into the intrinsic microstructures of polycrystalline SnSe based compounds

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Tin selenide (SnSe) compounds exhibit remarkable thermoelectric properties, largely attributed to their ultra-low lattice thermal conductivity.
• Strong phonon anharmonicity is a primary factor, but microstructural contributions are also significant.

Purpose of the Study:

• To investigate the microstructures of undoped SnSe and Bi-doped SnSe using transmission electron microscopy.
• To elucidate the role of microstructural features in reducing lattice thermal conductivity in SnSe-based materials.

Main Methods:

• Transmission electron microscopy (TEM) was employed to examine the microstructures.
• Analysis focused on grain morphology, grain boundaries, dislocations, and stacking faults.

Main Results:

• A characteristic microstructure of lath-like grains was observed in SnSe-based compounds.
• A high density of low-angle grain boundaries, edge dislocations, and stacking faults was identified within the grains.
• These defects induce lattice mismatch and distortion, serving as effective phonon scattering centers.

Conclusions:

• The observed microstructures, including lath-like grains and various defects, significantly contribute to the phonon scattering and thus the low thermal conductivity of SnSe.
• This work deepens the understanding of the mechanisms behind the excellent thermoelectric performance of SnSe-based compounds.