Hydrostatic Pressure Tuning of Thermal Conductivity for PbTe and PbSe Considering Pressure-Induced Phase Transitions.

Flexibly modulating thermal conductivity is of great significance to improve the application potential of materials. PbTe and PbSe are promising thermoelectric materials with pressure-induced phase transitions. Herein, the lattice thermal conductivities of PbTe and PbSe are investigated as a function of hydrostatic pressure by first-principles calculations. The thermal conductivities of both PbTe and PbSe in NaCl phase and phase exhibit complex pressure-dependence, which is mainly ascribed to the nonmonotonic variation of a phonon lifetime. In addition, the thermal transport properties of the phase behave anisotropically. The thermal conductivity of -PbTe is reduced below 1.1 W/m·K along the -axis direction at 7-12 GPa. The mean free path for 50% cumulative thermal conductivity increases from 7 nm for NaCl-PbSe at 0 GPa to 47 nm for the -PbSe in the -axis direction at 7 GPa, making it convenient for further thermal conductivity reduction by nanostructuring. The thermal conductivities of -PbTe in the -axis direction and -PbSe in the -axis direction are extremely low and hypersensitive to the nanostructure, showing important potential in thermoelectric applications. This work provides a comprehensive understanding of phonon behaviors to tune the thermal conductivity of PbTe and PbSe by hydrostatic pressure.