Heating a mixture of boron (impurities: carbon ∼ B50C2, boric acid – H3BO3) and tantalum (Ta) powders in nitrogen flow in a xenon high-flux optical furnace was performed. As-received powder composed of h-BN, H3BO3, TaB2, B9H11 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−1. 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−1, 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.

Results of the effect of concentrated light energy in a xenon high-flux optical furnace on transformation of boron nitride (BN) and boron (B) powders in a flow of nitrogen are presented. Raman, Auger Electron (AES), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning and transmission electron microscopes (SEM and TEM), and the measurement of band gap using transmittance technique have been employed for investigation of the properties of produced nanostructures. According Raman, AES and FTIR study the surface of all prepared nano powders is composed of BN. XRD disclosed pure amorphous boron inside particle. Gradient transformation pure boron to BN in the framework of one particle as well as layered nanostructure was observed by TEM study. Dependence of a square of the optical absorption coefficient for a deposited BN film versus the photon energy of incident light has confirmed a gradient and layered nature of the prepared BN nanostructures. * Corresponding AuthorFax: +380 (0) 44-4242131 E-Mail: sart@ipms.kiev.ua [a

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