Boron, the 5th element of the Periodic Table, is a nonmetallic, hard material with high melting point and boiling temperature. Despite decades of extensive investigations, boron and boron-rich solids remain in the focus of modern research, because there are many outstanding fundamental questions related to boron chemistry, crystal-chemistry, bonding, polymorphism, and physical properties of boron allotropes and compounds. There are also a number of theoretical predictions, which require experimental verification. New knowledge is gained by contemporary progress in material synthesis and methods of their investigations.
My research is aimed at the development of high-pressure high-temperature (HPHT) synthesis of single crystals of boron allotropes and boron-rich compounds, which can be used further for precise investigations of their structures, properties, and behavior at extreme conditions. The HPHT synthesis using the large-volume-press technique yields single crystals of especially high purity and quality. I performed the synthesis of inorganic materials at high pressures and high temperatures (boron-rich compounds, iron carbides, nanodiamonds, aluminum-nickel alloys) using the large-volume press with toroidal anvils (toroidal press) recently installed in the Laboratory of Crystallography. I contributed to the development of the toroidal cell assembly and conducted pressure and temperature calibrations of this new press.
Diamond anvil cell (DAC) technique was used for in situ studies of single crystals at high pressures and room temperature, as well as at extreme HPHT conditions with double-sided laser heating of samples in DACs. Various analytical techniques I used include synchrotron and in house XRD, Raman and infra-red (IR) spectroscopy, SEM and TEM.
In this study, I focused on high-pressure investigations of α-B, β-B and stoichiometric boron carbide, B13C2. The present work resulted in the HPHT synthesis of the previously unknown non-icosahedral boron allotrope, ζ-B, for the first-time and confirmed earlier theoretical predictions. Structural stability of α-B and β-B in the Mbar pressure range and B13C2 up to 73 GPa was experimentally proven. Careful tracing of the bond lengths in structures of these solids under compression shed light into mechanics of their HP behavior.