Isotope Effects on Thermal Conductivity of Boron Carbide

Abstract

The isotopically enriched disk samples of 10B4 12C, (10B0.75 11B0.25)4 12C, (10B0.20 11B0.80)4 12C, 10B4 13C, 10B4 (12C0.50 13C0.50), 11B4 (12C0.50 13C0.50), 11B4 12C, 11B4 13C and natural nB4 nC were prepared by the spark plasma sintering method. The thermal diffusivity for each sample was measured by the laser flash method over the temperature range from 290 to 1,450 K. The isotope effects on the thermal conductivities, which were calculated from the measured thermal diffusivities, the heat capacity for natural B4C and densities, were discussed in terms of the phonon-velocity and the scattering probability of phonon by isotopic impurity. The thermal conductivity decreased only with increasing the mean mass of boron. In the single-atom model, the phonon-velocity decreases with increasing the mass of atoms. The thermal conductivity obtained in this study was seen to be independent on the scattering probability of phonon by isotopic impurity, but to depend on the phonon-velocity. Isotope effects are thought to be difficult to detect in polycrystalline boron carbide.