ISSN Online: 2377-424X
ISBN Print: 978-1-56700-474-8
ISBN Online: 978-1-56700-473-1
International Heat Transfer Conference 16
NEGATIVE PRESSURE EFFECT ON THE THERMAL CONDUCTIVITY OF WURTZITE ZINC OXIDE
Abstrakt
The lattice thermal conductivity of wurtzite zinc oxide (w-ZnO) as a function of the pressure is investigated by combining first-principle calculations and the phonon Boltzmann equation. It is found that the room-temperature thermal conductivity of w-ZnO is 38.96 W/mK and 59.12 W/mK along the α and c crystal axis, respectively, showing obvious anisotropy. Moreover, the thermal conductivity decreases with pressure at low temperatures, while it slightly alters over the entire pressure region at room temperature. The results show that negative pressure dependent thermal conductivity at low temperatures is mainly attributed to the significant reduction of phonon relaxation time of acoustic and low-frequency optical modes with pressure, despite the enhancement of phonon group velocity. Further analysis indicates that the reduction of phonon relaxation time originates from the phonon anharmonicity, which is due to the large negative Grüneisen parameters. These results shed light on the role of pressure on the tuning of lattice thermal conductivity.