The influence of heat treatment upon the low temperature heat capacity of pyrolytic graphite

Abstract

Measurements of the specific heat of two specimens of pyrolytic graphite are reported in the temperature range 4° to 70°K. Following deposition under identical conditions, one of the samples had been heat treated at 2975°C for 1 hour. In the case of both specimens the lattice heat capacity at constant strain varied essentially as T2 between approximately 5° and 60°K, though the effect of the heat treatment was to reduce the specific heat by approximately 20% over the greater part of this range.

A representative set of results has been shown to accord well with the lattice dynamics of Komatsu. Although the effect of the heat treatment is consistent with an increase in c44, attention is drawn to the desirability of conducting further experiments before unambiguous physical significance might be attached to explanations permitted formally by the lattice dynamics.