The synthesis and characterization of B6O, B4C and ZrB2 at a pressure of 6 GPa

We obtained a series of B₆O, B₄C, ZrB₂ crystals at a pressure of 6 GPa and temperature of 1673–1973 K. These crystals were characterized by XRD and SEM. At a pressure of 6 GPa, the minimum synthesis temperature for B₆O is 1673 K. The grain size of B₆O in all the samples remained consistent at around 30–50 nm, with a uniform distribution in each sample. The bonding force between B₆O grains is weak, and the B₆O grain size remains relatively stable, showing minimal change with increasing temperature and time. In the sample synthesized at 1973 K, B₆O icosahedra (multiply twinned particles, MTPs) with a diameter of 12 μm, B₄C particles with a diameter of 25 μm, and flaky ZrB₂ were observed. We conducted theoretical calculations on B₆O and B₄C using density functional theory (DFT).