Measurement and calculation of the thermal expansion coefficient of diamond

Abstract

Abstract Measurements of the thermal expansion coefficient and pecific heat from room temperature to 850 K on 300 μm polycrystalline diamond samples are described. The extrapolated room temperature thermal expansion coefficient is similar to single crystal diamond (0.7 × 10 −6 ±0.3 × 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 increasing temperature the thermal expansion coefficient is clearly higher than the recommended values for single crystal diamond. Also, the specific heat is larger than recommended values for single crystal diamond above room temperature. The temperature dependence of specific heat provides the main contribution to temperature dependence of the thermal expansion coefficient. Calculation of the thermal expansion coefficient from measured specific heat provides a better fit to our measurements between 500 and 700 K than the recommended data.