Abstract
The thermal conductivity of a bulk sample of pyrolytic graphite has been measured from 3 to 300°K both perpendicular and parallel to the axis. Over the whole temperature range below 100°K the thermal conductivity in both directions appears to be limited by the crystallite size. The measured value of is 0.72 W/cm deg at 300°K, and decreases monotonically to 1.4× W/cm deg at 3°K. The measured anisotropy decreases monotonically from 47 at 300°K to 2.5 at 3°K. A theoretical calculation of the anisotropy from the elastic constants yields a value of 2.27 for K. A suggestion is offered to explain the rapid rise in the anisotropy with increasing temperature. Previous measurements of in natural and commercial graphite samples are much smaller.
- Received 21 March 1962
DOI:https://doi.org/10.1103/PhysRev.127.694
©1962 American Physical Society