Effect of concentrated light on morphology and vibrational properties of boron and tantalum mixtures.

Heating a mixture of boron (impurities: carbon ∼ BC, boric acid - HBO) and tantalum (Ta) powders in nitrogen flow in a xenon high-flux optical furnace was performed. As-received powder composed of h-BN, HBO, TaB, BH and a number of other phases including β-rhombohedral boron, apparently, heavily doped with Ta. FT-IR examination of any sample of the material reveals the complicated vibration spectrum containing, in particular, an absorption band near 2260 cm. The shapes of these bands are different for samples because powders were synthesized at different temperatures. Known, that in β-rhombohedral boron lattice, there are nano-sized voids of different types, which allow an accommodation of single atoms or small groups of atoms. Theoretical calculations performed by the method of quasi-classical type yields the same value, 2260 cm, for the vibrations frequency of Ta atoms in D-type crystallographic voids in β-rhombohedral boron lattice. Since, Ta atoms are known to prefer accommodation just in D-voids the experimentally detected bands can be identified with localized vibrations of Ta atoms.