Synergistically Tuning Thermoelectric Properties of BaCdPF via Strain Engineering

The layered BaCdPF compound with the ZrSiCuAs-type structure emerges as a promising thermoelectric (TE) material due to the excellent electronic transport properties under the <i>p</i>-type doping circumstance. However, the fundamental mechanisms that regulate its thermal and electronic transport under strain engineering remain largely unexplored, hindering its practical applications. In current work, the crystal structure, thermal transport, and electronic transport properties of layered BaCdPF under strain engineering are systematically investigated by first-principles calculations in combination with a machine-learning interatomic potential approach. The BaCdPF maintains mechanical robustness, high dynamic and thermal stabilities across a wide range of strain conditions. The coexistence of band degeneracy and anisotropic band dispersions (heavy and light bands) at the valence band maximum plays a critical role in enhancing electronic transport properties. Under tensile strain, the chemical bond softening and four-phonon scattering favors two-dimensional (2D) phonon transport characteristics, yielding a low lattice thermal conductivity of 1.08 W m^-1K^-1 at 300 K under a -4% tensile strain. Conversely, compressive strain significantly enhances the carrier mobility, promoting three-dimensional (3D) electronic transport. The current work not only provides effective strategies for optimizing the TE performance of layered BaCdPF but also sheds light on the distinct interplay of 3D charge and 2D phonon transport under strain engineering, which offers broader implications for the design of strain-modulated TE materials.