BASAL THERMAL CONDUCTIVITY OF HIGHLY ORIENTED PYROLYTIC GRAPHITE AS A FUNCTION OF DEGREE OF GRAPHITISATION

Measurements are reported of the temperature dependence of the thermal conductivity of well-oriented graphite deposited at 2100°-2200°C and heat-treated to various temperatures up to 3000°C. The results are analysed using the theory of crystallite-boundary limited conduction together with an empirical equation for the thermal resistance due to Umklapp processes. The theory leads to values of the crystallite dimension La parallel to the basal planes which are plotted as a function of heat treatment temperature and compared with similar values derived from electron-hole mobilities and X-ray studies on similar material. The value of La is quite well described by an exponential function of temperature for the values obtained from the thermal and electrical properties. The X-ray results are smaller by roughly a factor of ten. © 1969.