Thermal conductivity of crystalline C60 fullerite and that compacted from powder

We have studied thermal conductivity of both crystalline and compacted-powder C-60 fullerite at temperatures below 250 K. It was found that the observed temperature dependence k(T) of a pure C-60 crystal can be described qualitatively on the basis of the Debye-Peierls phonon model, though even in the best crystal the effective mean free path of phonons at low temperatures (lambda(p) less than or equal to 10(-5)cm) is much less than the crystal dimensions and is limited by scattering from defects. The thermal conductivity k of compacted samples is less than that of the crystalline sample and it can be sensitive to the method of the sample preparations and its temperature history. In the temperature range from 90 to 250 K the Einstein model of the heat transport in an array of buckyballs, vibrating with random phases, is in much better agreement with the observed k(T) dependence than the Debye model.