K. P. Burdina

High-Pressure Phase Transition of Hexagonal Alkali Pnictides

High-pressure studies of Li3P, Na3Sb, and Na3Bi at room temperature show that these compounds undergo a reversible transition from a hexagonal phase to a denser, cubic phase. The lattice parameters of the cubic phases are determined at pressures of up to 9.0 GPa.

On some alkali- and alkaline-earth-metal boron nitrides, unsaturated with boron

Abstract Three new lithium, magnesium and calcium boron nitrides, namely Ca6BN5(L), Mg6BN5(H) and Li3Mg3B2N5(L), were synthesized using a metal nitride–boron nitride sintering technique at low (L) or high (H) pressures. All these new compounds are typical metal boron nitride powders and, like previously known Mg3BN3, seem to have the N3− anion in their structures.

Cubic boron nitride synthesis by pyrolysis of certain polyammoniates of boron hydrides of metals at high pressure

Abstract Pyrolysis of certain polyammoniates of boron hydrides of metals (PABH Mes) at high pressures not exceeding 7.0 GPa and at a temperature not exceeding 1770 K was examined. These compounds have a general formula Me(BH4)n·mNH3, where n is determined by the metal valency, m=1–8, Me: Li, Mg, Zn, Al, Sc, La, Zr, Cr, Co. P,T regions of cubic boron nitride (cBN) synthesis in the process of PABH Me pyrolysis were determined. It was ascertained that the P,T regions differed widely for different compounds. The kinetics of cBN formation in the process of pyrolysis of PABH Mg and PABH Al were studied. Cubic boron nitride crystals were examined using the method of scanning electron microscopy (SEM). A mechanism of cubic boron nitride formation in the process of PABH Me pyrolysis is suggested.