The thermal expansion of graphite from 15 c. to 800 c.: part I. Experimental

The variation with temperature of the a and c unti-cell dimensions of hexagonal Ceylon graphite has been measured over the temperature range 15°-800°c. by the X-ray powder method. At 14°·6c., a =2.4562±0.0001 kx. c =6.6943±0.0007 kx. The carbon-carbon bond length, C-C=1.4210±0.0001a. The a dimension shows a slight contraction up to about 400°c., a small expansion occurring above this temperature. The thermal expansion in the c direction is large; the average value for a over the temperature range is 28.3 × 10 -6 . The complex nature of the expansion in both directions is discussed qualitatively.