Cyclic formation of boron suboxide crystallites into star-shaped nanoplates

Star-shaped boron suboxide (B6O) nanoplates were formed through a liquid-phase reaction of amorphous boron and boron oxide. The formation of the five-vertex B6O crystal is attributed to the oxygen-deficient state of B6Ox, where x < 1, which correlates to the lattice parameters. The mechanical properties of spark plasma sintered B6O show a hardness of 34.8 GPa and a fracture toughness of 4.0 MPa.m1/2. The understanding of the relationship between crystal atomic structure and crystal morphology could be employed in the design of other boron-rich compounds.