Effect of CaCO3 on carbothermic formation of hexagonal boron nitride (h-BN) was investigated. B2O3–C mixtures containing CaCO3 additive were reacted at 1500 for 120 min in nitrogen atmosphere. Formed phases in the reaction products were determined by powder-XRD analyses, and amounts of the constituents were determined by chemical analyses. Particle size and morphology of the formed h-BN powde...