Lattice thermal conductivity in layered BiCuSeO.

Area of Science:

• Materials Science
• Solid-State Physics
• Thermodynamics

Background:

• Bismuth copper selenide oxide (BiCuSeO) exhibits a high figure of merit, making it a promising thermoelectric material.
• Understanding the factors contributing to its thermal conductivity is crucial for optimizing thermoelectric performance.

Purpose of the Study:

• To quantify the low lattice thermal conductivity in layered BiCuSeO.
• To investigate the underlying mechanisms responsible for reduced thermal conductivity.
• To provide guidance for tuning the thermal properties of BiCuSeO.

Main Methods:

• Phonon dispersion analysis to understand scattering mechanisms.
• Quantification of lattice thermal conductivity contributions from acoustic and optical phonons.
• Analysis of phonon mean free path distribution at various temperatures.

Main Results:

• Acoustic to optical phonon scattering is significantly enhanced due to the unique phonon dispersion structure.
• Optical phonons contribute substantially (42%) to the lattice thermal conductivity at room temperature.
• Lattice thermal conductivity exhibits anisotropy, with a detailed distribution of phonon mean free paths determined.

Conclusions:

• The special phonon dispersion in BiCuSeO strongly enhances phonon scattering, leading to low lattice thermal conductivity.
• The significant contribution of optical phonons highlights their importance in heat transport.
• Understanding thermal anisotropy and phonon behavior provides a roadmap for engineering BiCuSeO's thermoelectric properties.