Thermal conductivity of high purity synthetic single crystal diamonds

Thermal conductivity of three high purity synthetic single crystalline diamonds has been measured with high accuracy at temperatures from 6 to 410 K. The crystals grown by chemical vapor deposition and by high-pressure high-temperature technique demonstrate almost identical temperature dependencies kappa(T) and high values of thermal conductivity, up to 24 W cm(-1) K-1 at room temperature. At conductivity maximum near 63 K, the magnitude of thermal conductivity reaches 285 W cm(-1) K-1, the highest value ever measured for diamonds with the natural carbon isotope composition. Experimental data were fitted with the classical Callaway model for the lattice thermal conductivity. A set of expressions for the anharmonic phonon scattering processes (normal and umklapp) has been proposed which gives an excellent fit to the experimental kappa(T) data over almost the whole temperature range explored. The model provides the strong isotope effect, nearly 45%, and the high thermal conductivity (> 24 W cm(-1) K-1) for the defect-free diamond with the natural isotopic abundance at room temperature.