Growth of boron suboxide crystals in the B–B2O3 system at high pressure and high temperature

Abstract
B6O crystal growth from the B–B2O3 system was investigated at 1700–2200 °C and 4.5–6.5 GPa by using two different sample assemblies. Single B6O crystals over 100 μm in size have been synthesized at 5.5 GPa and 2100 °C. This makes it possible to study the properties of this interesting material. The factors affecting the B6O crystal morphology, size, color, and growth process were discussed. The solubility of B6O in B2O3 flux was estimated at 5.5 GPa and different temperatures. On the basis of the experimental results, we suggest two methods to grow large B6O crystals.