Characterizations of several cubic phases directly transformed from the graphitic BC2N

The graphitic BC2N was transformed to cubic phases similar to diamond and cBN without any additive above 2150 °C under 7.7 GPa. X-ray diffraction patterns indicated that these cubic phases tended to segregate to cBN and diamond with increasing temperature to 2400 °C. This tendency was also supported by elemental mapping analysis of Auger electron spectroscopy (AES). Detailed spot analyses by AES, however, did not detect pure BN or C domains in the cubic crystals. This may imply that cBN grains contain tiny crystals of diamond and vice versa.