MEASUREMENT AND CALCULATION OF THE THERMAL-EXPANSION COEFFICIENT OF DIAMOND

Measurements of the thermal expansion coefficient and specific heat fr om room temperature to 850 K on 300 mu m polycrystalline diamond sampl es are described. The extrapolated room temperature thermal expansion coefficient is similar to single crystal diamond (0.7 x 10(-6) +/- 0.3 x 10(-6) K-1). At 313 K the measured specific heat is 7.05 J mol(-1) K-1 which agrees with the recommended single crystal data. With increa sing temperature the thermal expansion coefficient is clearly higher t han the recommended values for single crystal diamond. Also, the speci fic heat is larger than recommended values for single crystal diamond above room temperature. The temperature dependence of specific heat pr ovides the main contribution to temperature dependence of the thermal expansion coefficient. Calculation of the thermal expansion coefficien t from measured specific heat provides a better fit to our measurement s between 500 and 700 K than the recommended data. (C) 1997 Elsevier S cience S.A.