Transformation of boron nitride under high pressure and shear deformation

Abstract

Boron nitride cannot be found in nature and can be only synthesized. BN is isoelectronic to carbon and, like carbon, can exist as several polymorphic modifications. It is important material for many applications due to its prominent mechanical, chemical, and thermal properties. In our study, we consider certain phase transformations of boron nitride treated in a high-pressure diamond anvil cell with shear deformation. We studied wurtzitic BN (wBN) treated under pressure from 8 to 17 GPa and graphite-like BN (hBN) treated under pressure from 2.5 to 6 GPa with different shear deformation degrees. The samples were studied in a transmission electron microscope (TEM). It was found that wBN transforms into hBN under 8 GPa and 20°-shear angle, and forms onion-like curved structures. We have analyzed our results and characterized transformations of hBN under pressure up to 20 GPa and shear deformation.