Evidence of interstitial-mediated boron self-diffusion in boron carbide

Abstract

Boron carbide is an important high-temperature material with interesting structural and functional properties. However, self-diffusion is very poorly known on this material, and also the few impurity diffusion studies, devoted in particular to helium and lithium, overlook the possible diffusion coupling with intrinsic defects. In this paper we present a study of boron self-diffusion in boron carbide based on first principles calculations and kinetic cluster expansion. Our results show that boron self-diffusion may occur with a migration activation energy on the order of 1.5–1.6 eV and with a global activation energy between 4 and 5.5 eV, depending on the doping conditions, which is significantly lower than the self-diffusion activation energies in other semiconducting carbides, like silicon carbide.We believe that our results are of interest for many applications of boron carbide and for tuning the best conditions for controlling the synthesis routes at specific stoichiometries for boron carbide.