Experimental measurement of thermal conductivity along different crystallographic planes in graphite

Abstract

In this work, the time-domain thermoreflectance (TDTR) method is used to measure the thermal conductivity of graphite along different crystallographic planes at room temperature for the first time and the thermal conductivities along the non-principal axes of graphite are obtained. A focused ion beam is used to cut graphite samples along different crystallographic planes for the TDTR measurement. Then, a thermal model is developed to extract the thermal conductivity of graphite along different crystallographic planes from the measured signals of the TDTR method. The measured thermal conductivities along different crystallographic planes in graphite agree well with the anisotropy model, revealing that the traditional TDTR method can be used to measure the non-principal axis thermal conductivity of anisotropic layered materials. Moreover, the experimental results demonstrate that once the crystallographic plane deviates from the cross-plane direction, the in-plane phonon modes will dominate the heat transfer in graphite.