Room-temperature transition of rhombohedral-type boron nitride under high static pressure

Abstract
Rhombohedral-type boron nitride (rBN) has been studied to pressures of 61 GPa at room temperature in a diamond-anvil cell by in situ x-ray diffraction. Synchrotron radiation was employed as an x-ray source. A precursory structural change occurs at ∼5 GPa. A transition to the cubic zinc-blende form (cBN) takes place at ∼8 GPa and is completed above 20 GPa. For pressurization above 55 GPa, the cubic phase can be quenched to the ambient pressure.