Effect of isotopic purity on thermal conductivity of boron nitride: A theoretical study

In this letter we report the theoretical study of the effect of isotopic purity on the temperature dependence of the lattice thermal conductivity of cubic BN single crystals. The maximum thermal conductivity of pure BN is very high (∼105 W/m/K) and it is comparable to the thermal conductivity of the carbon nanotube. It is two orders of magnitude higher than that of BN with 50% 10B. We find that the very high contribution (∼ 95%) of the usually neglected N-drift scattering at the thermal conductivity peak is the reason for such an increase in thermal conductivity of pure BN, compared to that of natural BN. The thermal conductivity is nearly symmetric with respect to the isotopic composition of boron and it is minimum for 50% 10B and 50% 11B. The role of phonon scattering by boron isotopes present in BN, in controlling the temperature dependence of thermal conductivity has been accurately quantified