Petr S. Sokolov

On melting of B4C boron carbide under pressure

The pressure dependence of melting temperatures for boron carbide and B4C-carbon eutectic has been studied up to 8 GPa, and it was found that in both cases the melting curves exhibit negative slope (−13 ± 6 K/GPa), that is indicative of higher density of the melt as compared to the solid phase.

Self-propagating high-temperature synthesis of boron phosphide

A new method of producing boron phosphide (BP) submicron powders by a self-propagating high-temperature reaction between boron phosphate and magnesium in the presence of an inert diluent (sodium chloride) has been proposed. Bulk polycrystalline BP with microhardness of HV = 28(2) GPa has been prepared by sintering the above powders at 7.7 GPa and 2600 K.

On melting of silicon carbide under pressure

The melting of silicon carbide has been studied at pressures 5–8 GPa and temperatures up to 3300 K. It has been found that SiC melts congruently, and its melting curve has negative slope of −44 ± 4 K/GPa.

Self-propagating high-temperature synthesis of boron subphosphide B12P2

Two new methods to produce nanopowders of B12P2 boron subphosphide by self-propagating high-temperature synthesis have been proposed. Bulk polycrystalline B12P2 with microhardness of HV = 35(3) GPa and stability in air up to 1300 K has been prepared by sintering these powders at 5.2 GPa and 2500 K.

Optical phonon modes in rhombohedral boron monosulfide under high pressure

Raman spectra of rhombohedral boron monosulfide (r-BS) were measured under pressures up to 34 GPa at room temperature. No pressure-induced structural phase transition was observed, while strong pressure shift of Raman bands towards higher wavenumbers has been revealed. IR spectroscopy as a complementary technique has been used in order to completely describe the phonon modes of r-BS. All experimentally observed bands have been compared with theoretically calculated ones and modes assignment has been performed. r-BS enriched by 10B isotope was synthesized, and the effect of boron isotopic substitution on Raman spectra was observed and analyzed.Raman spectra of rhombohedral boron monosulfide (r-BS) were measured under pressures up to 34 GPa at room temperature. No pressure-induced structural phase transition was observed, while strong pressure shift of Raman bands towards higher wavenumbers has been revealed. IR spectroscopy as a complementary technique has been used in order to completely describe the phonon modes of r-BS. All experimentally observed bands have been compared with theoretically calculated ones and modes assignment has been performed. r-BS enriched by 10B isotope was synthesized, and the effect of boron isotopic substitution on Raman spectra was observed and analyzed.

Congruent melting and rapid single-crystal growth of ZnO at 4 GPa

Transparent, colorless and contamination-free ZnO single crystals have been grown by rapid crystallization from the melt at ∼4 GPa and ∼1700 K. Recovered crystals exhibit needle-like (along the [0001] direction) morphology and have sizes up to 2 mm in length and 0.2 mm dia. Wurtzite structure (P63mc) has been confirmed by single-crystal X-ray diffraction, and lattice parameters (a = 3.2474(5) A, c = 5.2017(7) A) are in good agreement with literature data. Photoluminescence measurements revealed an intensive violet line at 398 nm, whose intensity depends non-linearly on the laser excitation power due to collective effects in photoexcited charge carriers or/and an effect of the stimulated emission in the ZnO crystals under study.

Melting of B12P2 boron subphosphide under pressure

ABSTRACT Melting of boron subphosphide (B12P2) to 26 GPa has been studied by in situ synchrotron X-ray powder diffraction in a laser-heated diamond anvil cell, and by quenching and electrical resistance measurements in a toroid-type high pressure apparatus. B12P2 melts congruently, and the melting curve has a positive slope of 23(6) K/GPa. No solid-state phase transition was observed up to the melting in the whole pressure range under study.