Question

Modulating temperature dependence of thermal conductivity by nanostructuring

Answer 1

At around room temperature and higher, thermal conductivity of single crystal commonly decreases as temperature increases and shows negative temperature dependence. Crystals with positive temperature dependence, which is often preferred in thermal management, requires high Debye temperature. While this narrows the selection of material candidate, the effective Debye temperature can be enhanced through nanostructuring the single crystals. By investigating heat conduction in nanocrystalline silicon, silicon carbide, and diamond, we here demonstrate that shift of temperature dependence of heat capacity and decrease in magnitude of negative temperature dependence of relaxation time by nanostructuring lead to positive temperature dependence of thermal conductivity.